To cause an  allergic dermatitis  reaction, the urushiol is first oxidized to create two double-bonded oxygens on the chemical. It then reacts with a protein  nucleophile  to trigger a reaction within the skin.  Dermatitis  is mediated by an  acquired immune response . Urushiol is too small to directly activate an immune response. Instead, it attaches to certain proteins of the skin, where it acts as a  hapten , leading to a  type IV hypersensitivity  reaction. [ 21 ] [ self-published source? ] [ 22 ]


Hydrocortisone , the active ingredient in cortisone, works to alleviate this condition by stopping the release of chemicals that cause the dermatitis reaction. [ 23 ]  Hydrocortisone itself does not react with urushiol in any way.


Valdecoxib  is a  nonsteroidal anti-inflammatory drug  (NSAID) used in the treatment of  osteoarthritis ,  rheumatoid arthritis , and painful  menstruation  and menstrual symptoms. It is a selective  cyclooxygenase-2 inhibitor . It was patented in 1995. [ 2 ]


Valdecoxib was manufactured and marketed under the brand name  Bextra  by  G. D. Searle & Company  as an anti-inflammatory arthritis drug. [ 3 ]  It was approved by the United States  Food and Drug Administration  (FDA) on November 20, 2001, to treat arthritis and menstrual cramps, [ 4 ] [ 5 ]  and was available by prescription in tablet form until 2005 when the FDA requested that Pfizer withdraw Bextra from the American market. [ 6 ]  The FDA cited "potential increased risk for serious cardiovascular (CV) adverse events," an "increased risk of serious skin reactions" and the "fact that Bextra has not been shown to offer any unique advantages over the other available NSAIDs." [ 6 ]


In 2009, Bextra was at the center of the "largest health-care fraud settlement and the largest criminal fine of any kind ever." [ 4 ] [ 7 ]  Pfizer paid a $2.3 billion civil and criminal fine.  Pharmacia & Upjohn , a Pfizer subsidiary, violated the United States  Food, Drug and Cosmetic Act  for misbranding Bextra "with the intent to defraud or mislead." [ 3 ]


A water-soluble and injectable  prodrug  of valdecoxib,  parecoxib , is marketed in the  European Union  under the tradename Dynastat.


In the United States, the FDA approved valdecoxib for the treatment of  osteoarthritis , adult  rheumatoid arthritis , and primary  dysmenorrhea . [ 8 ]


Valdecoxib was also used  off-label  for controlling acute pain and various types of surgical pain. [ 8 ]


On April 7, 2005, Pfizer withdrew Bextra from the U.S. market on recommendation by the FDA, citing an increased risk of  heart attack  and  stroke  and also the risk of a serious, sometimes fatal, skin reaction. This was a result of recent attention to prescription NSAIDs, such as  Merck's   Vioxx . Other reported side effects were  angina  and  Stevens–Johnson syndrome .


Pfizer first acknowledged cardiovascular risks associated with Bextra in October 2004. The  American Heart Association  soon after was presented with a report indicating patients using Bextra while recovering from heart surgery were 2.19 times more likely to suffer a stroke or heart attack than those taking  placebos .


In a large study published in  The Journal of the American Medical Association  in 2006, valdecoxib appeared less adverse for renal (kidney) disease and heart arrhythmia compared to Vioxx, but elevated renal risks were slightly suggested. [ 9 ]


On September 2, 2009, the  United States Department of Justice  fined Pfizer $2.3 billion after one of its  subsidiaries , Pharmacia & Upjohn Company, pleaded guilty to marketing four drugs, including Bextra, "with the intent to defraud or mislead." [ 10 ]  Pharmacia & Upjohn admitted to criminal conduct in the promotion of Bextra, and agreed to pay the largest criminal fine ever imposed in the United States for any matter, $1.195 billion. [ 11 ]  A former Pfizer district sales manager was  indicted  and sentenced to home confinement for destroying documents regarding the illegal promotion of Bextra. [ 12 ] [ 13 ]  In addition, a regional manager pleaded guilty to distribution of a misbranded product, and was fined $75,000 and 24 months on probation. [ 14 ]


The remaining $1 billion of the fine were paid to resolve allegations under the civil  False Claims Act  case and is the largest civil fraud settlement against a pharmaceutical company. Six whistleblowers were awarded more than $102 million for their role in the investigation. [ 15 ]  Former Pfizer sales representative John Kopchinski acted as a  qui tam  relator and filed a complaint in 2004 outlining the illegal conduct in the marketing of Bextra. [ 16 ]  Kopchinski was awarded $51.5 million for his role in the case because the improper marketing of Bextra was the largest piece of the settlement at $1.8 billion. [ 17 ]


Several HPLC-UV methods [ 18 ]  have been reported for valdecoxib estimation in biological samples like human urine. [ 19 ] [ 20 ]  Valdecoxib has analytical methods for bioequivalence studies, [ 21 ] [ 22 ]  metabolite determination, [ 23 ] [ 24 ] [ 19 ]  estimation of formulation, [ 25 ]  and an HPTLC method for simultaneous estimation in tablet dosage form. [ 26 ]


This is a list of  allergies , which includes the  allergen , potential reactions, and a brief description of the cause where applicable.


Many substances can cause an allergic reaction when in contact with the human  integumentary system .


Many  skin conditions  require a  skin biopsy  for confirmation of the diagnosis.  With several of these conditions there are features within the cells contained in the skin biopsy specimen that have elements in their cytoplasm or nucleus that have a characteristic appearance unique to the condition.  These elements are termed  inclusion bodies .


There are many different  keratin  proteins normally expressed in the human  integumentary system .


Acropustulosis  refers to  acrodermatitis  with  pustular  involvement.


Types include:


Albinism  is a  congenital condition  characterized in humans by the partial or complete absence of  pigment  in the skin, hair and eyes. Albinism is associated with a number of vision defects, such as  photophobia ,  nystagmus , and  amblyopia . Lack of skin pigmentation makes for more susceptibility to sunburn and skin cancers. In rare cases such as  Chédiak–Higashi syndrome , albinism may be associated with deficiencies in the transportation of melanin granules. This also affects essential granules present in immune cells, leading to increased susceptibility to infection. [ 3 ]


Albinism results from inheritance of  recessive gene   alleles  and is known to affect all  vertebrates , including  humans . It is due to absence or defect of  tyrosinase , a copper-containing enzyme involved in the production of  melanin . Unlike humans, other animals have multiple  pigments  and for these,  albinism  is considered to be a hereditary condition characterised by the absence of melanin in particular, in the eyes, skin, hair, scales, feathers or cuticle. [ 4 ]  While an organism with complete absence of melanin is called an albino, an organism with only a diminished amount of melanin is described as  leucistic  or albinoid. [ 5 ]  The term is from the  Latin   albus , "white".


There are two principal types of albinism:  oculocutaneous , affecting the eyes, skin and hair, and  ocular  affecting the eyes only.


There are different types of oculocutaneous albinism depending on which gene has undergone mutation. With some there is no pigment at all. The other end of the spectrum of albinism is "a form of albinism called rufous oculocutaneous albinism, which usually affects dark-skinned people". [ 6 ]


According to the  National Organization for Albinism and Hypopigmentation , "With ocular albinism, the color of the iris of the eye may vary from blue to green or even brown, and sometimes darkens with age. However, when an optometrist or ophthalmologist examines the eye by shining a light from the side of the eye, the light shines back through the iris since very little pigment is present." [ 7 ]


Because individuals with albinism have skin that entirely lacks the dark pigment melanin, which helps protect the skin from the sun's  ultraviolet   radiation , their skin can  burn  more easily from overexposure. [ 8 ]


The human eye normally produces enough pigment to color the  iris  blue, green or brown and lend opacity to the eye. In photographs, those with albinism are more likely to demonstrate "red eye", due to the red of the  retina  being visible through the iris. Lack of pigment in the eyes also results in problems with vision, both related and unrelated to  photosensitivity . [ 9 ]


Those with albinism are generally as healthy as the rest of the population (but see related disorders below), with growth and development occurring as normal, and albinism by itself does not cause mortality, [ 10 ]  although the lack of pigment blocking  ultraviolet   radiation  increases the risk of melanomas (skin cancers) and other problems. [ 11 ]


Development of the optical system is highly dependent on the presence of melanin. For this reason, the reduction or absence of this pigment in people with albinism may lead to:


Eye conditions common in albinism include:


The improper development of the  retinal pigment epithelium  (RPE), which in normal eyes absorbs most of the reflected sunlight, further increases glare due to light scattering within the eye. [ 13 ]  The resulting sensitivity (photophobia) generally leads to discomfort in bright light, but this can be reduced by the use of sunglasses or brimmed hats. [ 14 ]


Oculocutaneous albinism  is generally the result of the  biological inheritance  of  genetically recessive   alleles  ( genes ) passed from both parents of an individual such as  OCA1  and  OCA2 .  A mutation in the human TRP-1 gene may result in the deregulation of melanocyte tyrosinase enzymes, a change that is hypothesized to promote brown versus black melanin synthesis, resulting in a third oculocutaneous albinism (OCA) genotype, "OCA3". [ 15 ]  Some rare forms are inherited from only one parent. There are other  genetic mutations  which are proven to be associated with albinism. All alterations, however, lead to changes in melanin production in the body. [ 10 ] [ 16 ]


The chance of offspring with albinism resulting from the pairing of an organism with albinism and one without albinism is low. However, because organisms (including humans) can be carriers of genes for albinism without exhibiting any traits, albinistic offspring can be produced by two non-albinistic parents. Albinism usually occurs with equal frequency in both sexes. [ 10 ]  An exception to this is  ocular albinism , which it is passed on to offspring through X-linked inheritance. Thus, ocular albinism occurs more frequently in males as they have a single X and Y  chromosome , unlike females, whose genetics are characterized by two X chromosomes. [ 17 ]


There are two different forms of albinism: a partial lack of the melanin is known as hypomelanism, or hypomelanosis, and the total absence of melanin is known as  amelanism  or amelanosis. [ 18 ]


The enzyme defect responsible for OCA1-type albinism is tyrosine 3-monooxygenase (tyrosinase), which synthesizes melanin from the amino acid  tyrosine .
 [ 19 ]


It is suggested that the early genus  Homo  (humans in the broader sense) started to evolve in East Africa around 3 million years ago. [ 20 ]  The dramatic  phenotypic  change from the ape-like  Australopithecus  to early  Homo  is hypothesized to have involved the extreme loss of body hair – except for areas most exposed to UV radiation, such as the head – to allow for more efficient  thermoregulation  in the early hunter-gatherers. The skin that would have been exposed upon general body hair loss in these early proto-humans would have most likely been non-pigmented, reflecting the pale skin underlying the hair of our chimpanzee relatives. A positive advantage would have been conferred to early hominids inhabiting the African continent that were capable of producing darker skin – those who first expressed the  eumelanin -producing  MC1R   allele  – which protected them from harmful epithelium-damaging ultraviolet rays. Over time, the advantage conferred to those with darker skin may have led to the prevalence of darker skin on the continent. The positive advantage, however, would have had to be strong enough so as to produce a significantly higher reproductive fitness in those who produced more melanin. The cause of a selective pressure strong enough to cause this shift is an area of much debate. Some hypotheses include the existence of significantly lower reproductive fitness in people with less melanin due to lethal skin cancer, lethal kidney disease due to excess  vitamin D  formation in the skin of people with less melanin, or simply natural selection due to mate preference and sexual selection. [ 20 ]


When comparing the prevalence of albinism in Africa to its prevalence in other parts of the world, such as Europe and the United States, the potential evolutionary effects of skin cancer as a selective force due to its effect on these populations may not be insignificant. [ 20 ]  It would follow, then, that there would be stronger selective forces acting on albino individuals in Africa than on albinos in Europe and the US. [ 21 ]  In two separate studies in Nigeria, very few people with albinism appear to survive to old age. One study found that 89% of people diagnosed with albinism are between 0 and 30 years of age, while the other found that 77% of albinos were under the age of 20. [ 21 ]


However, it has also been theorized that albinism may have been able to spread in some Native American communities, because albino males were culturally revered and assumed as having divine origins. The very high incidence of albinism among the Hopi tribe has been frequently attributed to the privileged status of albino males in Hopi society, who were not required to perform physical work outdoors, shielding them from the harmful effects of UV radiation. This privileged status of albino males in Hopi society allowed them to reproduce with large numbers of non-albino women, spreading the genes that are associated with albinism. [ 22 ] [ 23 ]


Genetic testing  can confirm albinism and what variety it is, but offers no medical benefits, except in the case of non-OCA disorders. Such disorders cause other medical problems in conjunction with albinism, and may be treatable. Genetic tests are currently available for parents who want to find out if they are carriers of ty-neg albinism. Diagnosis of albinism involves carefully examining a person's eyes, skin and hairs. Genealogical analysis can also help.


Albinism can also be a feature of several syndromes: [ 24 ]


Since there is no cure for albinism, it is managed through lifestyle adjustments. People with albinism need to take care not to get sunburnt and should have regular healthy skin checks by a dermatologist. [ citation needed ]


For the most part, treatment of the eye conditions consists of visual rehabilitation. Surgery is possible on the  extra-ocular muscles  to decrease  strabismus . [ 8 ]   Nystagmus -damping surgery can also be performed, to reduce the "shaking" of the eyes back and forth. [ 25 ]  The effectiveness of all these procedures varies greatly and depends on individual circumstances. [ citation needed ]


Glasses  (often with tinted lenses), low vision aids,  large-print  materials, and bright angled reading lights can help individuals with albinism. Some people with albinism do well using  bifocals  (with a strong reading lens), prescription reading glasses, hand-held devices such as  magnifiers  or  monoculars  or wearable devices like  eSight
and  Brainport . [ 14 ] [ 26 ]


The condition may lead to abnormal development of the  optic nerve  and sunlight may damage the  retina  of the eye as the  iris  cannot filter out excess light due to a lack of pigmentation.  Photophobia  may be ameliorated by the use of sunglasses which filter out ultraviolet light. [ 27 ]  Some use  bioptics , glasses which have small telescopes mounted on, in, or behind their regular lenses, so that they can look through either the regular lens or the telescope. Newer designs of bioptics use smaller light-weight lenses. Some US states allow the use of bioptic telescopes for driving motor vehicles. [ citation needed ]  (See also  NOAH  bulletin "Low Vision Aids".)


There are a number of national support groups across the globe which come under the umbrella of the World Albinism Alliance. [ 28 ]


Albinism affects people of all ethnic backgrounds; its frequency worldwide is estimated to be approximately one in 17,000. Prevalence of the different forms of albinism varies considerably by population, and is highest overall in people of  sub-Saharan  African descent. [ 29 ]  Today, the prevalence of albinism in  sub-Saharan Africa  is around 1 in 5,000, while in Europe and the US it is around 1 in 20,000 of the European derived population. [ 30 ] [ 20 ]  Rates as high as 1 in 1,000 have been reported for some populations in Zimbabwe and other parts of  Southern Africa . [ 21 ]


Certain ethnic groups and populations in isolated areas exhibit heightened susceptibility to albinism, presumably due to genetic factors. These include notably the  Native American   Kuna ,  Zuni  and  Hopi  nations (respectively of  Panama ,  New Mexico  and  Arizona );  Japan , in which one particular form of albinism is unusually common (OCA 4); [ 31 ]  and  Ukerewe Island , the population of which shows a very high incidence of albinism. [ 32 ]


In some  Native American  and  South Pacific  cultures, people with albinism have been traditionally revered, because they were considered heavenly beings associated with the  sky . [ 34 ] [ 35 ]  Among various indigenous tribes in  South America , albinos were able to live luxurious lives due to their divine status. [ 36 ]  This special status was applied mainly to male albinos. [ 37 ]  It has been theorized that the very high level of albinism among some Native American tribes can be attributed to sexual privileges given to male albinos, which allowed them to reproduce with large numbers of non-albino women in their tribes, leading to the spread of genes that are associated with albinism. [ 34 ]


Humans with albinism often face social and cultural challenges (even threats), as the condition is often a source of ridicule, discrimination, or even fear and violence. It is especially socially stigmatised in many African societies. A study conducted in Nigeria on albino children stated that "they experienced alienation, avoided social interactions and were less emotionally stable. Furthermore, affected individuals were less likely to complete schooling, find employment, and find partners". [ 38 ]  Many cultures around the world have developed beliefs regarding people with albinism. [ citation needed ]


In African countries such as  Tanzania [ 39 ]  and  Burundi , [ 40 ] [ 41 ]  there has been an unprecedented rise in  witchcraft -related killings of people with albinism in recent years, because their body parts are used in potions sold by  witch doctors . [ 42 ]  Numerous authenticated incidents have occurred in Africa during the 21st century. [ 43 ] [ 44 ] [ 45 ] [ 46 ]  For example, in Tanzania, in September 2009, three men were convicted of killing a 14-year-old albino boy and severing his legs in order to sell them for witchcraft purposes. [ 47 ]   Again in Tanzania and Burundi in 2010, the murder and dismemberment of a kidnapped albino child was reported from the courts, [ 40 ]  as part of a continuing problem.  The US-based  National Geographic Society  estimated that in Tanzania a complete set of albino body parts is worth  US$ 75,000. [ 48 ] [ 49 ]


Another harmful and false belief is that sex with an albinistic woman will cure a man of  HIV . This has led, for example in  Zimbabwe , to rapes (and subsequent HIV infection). [ 50 ]


Famous people with albinism include historical figures such as  Oxford  don  William Archibald Spooner ; actor-comedian  Victor Varnado ; musicians such as  Johnny  and  Edgar Winter ,  Salif Keita ,  Winston "Yellowman" Foster ,  Brother Ali ,  Sivuca ,  Hermeto Pascoal ,  Willie "Piano Red" Perryman ,  Kalash Criminel ; actor-rapper  Krondon , and fashion models  Connie Chiu , Ryan "La Burnt" Byrne and  Shaun Ross .   Emperor Seinei  of Japan is thought to have albinism because he was said to have been born with white hair. [ citation needed ]


International Albinism Awareness Day  was established after a motion was accepted on 18 December 2014 by the  United Nations General Assembly , proclaiming that 13 June would be known as International Albinism Awareness Day as of 2015. [ 51 ]   This was followed by a mandate created by the  United Nations Human Rights Council  that appointed  Ms. Ikponwosa Ero , who is from Nigeria, as the first Independent Expert on the enjoyment of human rights by persons with albinism. [ 52 ]


Amelanism  (also known as  amelanosis ) is a pigmentation abnormality characterized by the lack of  pigments  called  melanins , commonly associated with a  genetic  loss of  tyrosinase  function. Amelanism can affect  fish ,  amphibians ,  reptiles ,  birds , and  mammals  including humans.  The appearance of an amelanistic animal depends on the remaining non-melanin pigments.  The opposite of amelanism is  melanism , a higher percentage of melanin. [ citation needed ]


A similar condition,  albinism , is a hereditary condition characterised in animals by the absence of pigment in the eyes, skin, hair, scales, feathers or cuticle. [ 1 ]  This results in an all white animal, usually with pink or red eyes.


Melanin  is a compound found in  plants ,  animals , and  protists , and is derived from the  amino acid   tyrosine . Melanin is a  photoprotectant , absorbing the  DNA-damaging   ultraviolet  radiation of the sun.  Vertebrates  have melanin in their  skin  and  hair ,  feathers , or  scales . They also have two layers of pigmented tissue in the eye: the  stroma , at the front of the  iris , and the  iris pigment epithelium , a thin but critical layer of pigmented cells at the back of the iris. Melanin is also present in the  inner ear , and is important for the early development of the  auditory system . [ 2 ]  Melanin is also found in parts of the  brain  and  adrenal gland . [ citation needed ]


Melanins are produced in  organelles  called  melanosomes . The production of melanins is called  melanogenesis . Melanosomes are found in specialized pigment cells called  melanocytes , but may also be engulfed by other cells, which are then called melanophages. Hair acquires pigment from melanocytes in the root bulb, which deposit melanosomes into the growing hair structure. A critical step in the production of melanins is the  catalysis  of  tyrosine  by an  enzyme  called  tyrosinase , producing dopaquinone. Dopaquinone may become eumelanin, or phaeomelanin. Eumelanin, meaning  true black , is a dense  compound  that absorbs most wavelengths of light, and appears black or brown as a result. Phaeomelanin, meaning  rufous-black , is characterized by the presence of  sulfur -containing  cysteine , and it appears reddish to yellowish as a result. Melanosomes containing eumelanin are eumelanosomes, while those containing phaeomelanin are phaeomelanosomes.  Melanocyte-stimulating hormone  (MSH) binds to the  Melanocortin 1 receptor  (MC1R) and commits melanocytes to the production of eumelanin. In the absence of this signal, melanocytes produce phaeomelanin. Another chemical,  Agouti signalling peptide  (ASP), can attach itself to MC1R and interfere with MSH/MC1R signalling. In many mammals, variation in the level of ASP switches melanocytes between eumelanin and phaeomelanin production, resulting in coloured patterns.


Melanocytes, and the parallel  melanophores  found in fishes, amphibians, and reptiles, are derived from a strip of tissue in the  embryo  called the  neural crest .  Stem cells  in the neural crest give rise to the cells of the  autonomic nervous system , supportive elements of the skeleton such as  chondrocytes , cells of the  endocrine system , and melanocytes. This strip of tissue is found along the dorsal midline of the  embryo , and  multipotent  cells migrate down along the sides of the embryo, or through  germ layers , to their ultimate destinations. Melanocyte stem cells are called melanoblasts. Conditions associated with abnormalities in the migration of melanoblasts are known collectively as  piebaldism . Pigment cells of the  iris pigment epithelium  have a separate embryological origin. [ 3 ]  Piebaldism and amelanism are distinct conditions.


The only pigments that mammals produce are melanins. For a mammal to be unable to chemically manufacture melanin renders it completely pigmentless. This condition is more commonly called  albinism . Amelanistic mammals have white hair, pink skin, and eyes that have a pink, red, or violet appearance. Reddish eyes are due to the lack of pigment in the  iris pigment epithelium . When the  stroma  is unpigmented but the iris pigment epithelium is not, mammalian eyes appear blue. Melanin in the pigment epithelium is critical for visual acuity and contrast. [ 4 ]


Loss of melanogenesis function is linked to the  gene  that encodes  tyrosinase . Certain  alleles  of this gene,  TYR , at the  Color  locus, cause  oculocutaneous albinism type 1  in humans and the familiar red-eyed albino conditions in  mice  and other mammals.


Other vertebrates, such as fishes, amphibians, reptiles and birds, produce a variety of non-melanin  pigments . Disruption of melanin production does not affect the production of these pigments. Non-melanin pigments in other vertebrates are produced by cells called  chromatophores . Within this categorization, xanthophores are cells that contain primarily yellowish pteridines, while erythrophores contain primarily orangish  carotenoids . Some species also possess iridophores or leucophores, which do not contain true pigments, but light-reflective structures that give iridescence. An extremely uncommon type of chromatophore, the cyanophore, produces a very vivid blue pigment. [ 5 ]  Amelanism in fishes, amphibians, reptiles and birds has the same  genetic   etiology  as in mammals: loss of  tyrosinase  function. However, due to the presence of other pigments, other amelanistic vertebrates are seldom white and red-eyed like amelanistic mammals.


Melanocytes depend on the  Melanocortin 1 receptor  (MC1R) to signal the production of eumelanin. Loss of melanocortin 1 receptor function or high activity of the MC1R-antagonist,  Agouti signalling peptide , can cause the widespread absence of eumelanin. Loss of MC1R function, a recessive trait, has been observed in many species. In humans, various  mutations  of the  MC1R  gene result in  red hair ,  blond hair , fair skin, and susceptibility to sundamaged skin and  melanoma . [ 6 ]  Aeumelanic hair coats, associated with mutations of the  MC1R  gene, have also been identified in mice, [ 7 ]  cattle, [ 8 ]  dogs, [ 9 ]  and horses. [ 10 ]  These coat colors are called "yellow" in mice and dogs, "red" in cattle and  chestnut  in horses. The loss of eumelanin in the coat is, in these species, harmless. The distinction between aeumelanism and hyperphaeomelanism – over abundance of phaeomelanin – is semantic.


Aphaeomelanism is the abnormal absence of phaeomelanin from the  integumentary system  and/or eyes. [ 11 ]  Phaeomelanin is produced by melanocytes in the absence of melanocortin 1 receptor. This absence is mediated by agouti signalling protein, which antagonizes melanocortin 1 receptor. Loss of function of agouti signalling protein can permit unmediated eumelanin production, producing a uniformly black-to-brown coat color. This condition can be observed in dogs, [ 12 ]  cats, [ 13 ]  and horses. [ 14 ]  The appearance of mammals with recessive agouti mutations is typically dense black. As with aeumelanism, the difference between lack of phaeomelanin and abundance of eumelanin is one of words. Some agouti alleles in mice are associated with health defects, but this is not the case in dogs, cats, or horses.


Atrophoderma  refers to conditions involving thinning of skin. [ 1 ]


Atypia  (from  Greek ,  a  +  typos , without type; a condition of being irregular or nonstandard) [ 1 ]  is a  histopathologic  term for a structural abnormality in a  cell , i.e. it is used to describe atypical cells.


Atypia can be caused by infection or irritation. If, for example it were diagnosed in a  Pap smear  in the  uterus  it is more likely to be precancerous.


The related concept of  dysplasia  refers to an abnormality of development, [ 2 ]  and includes abnormalities on larger,  histopathologic  scales.


Features that constitute atypia have different definitions for different diseases, but often include the following  nucleus  abnormalities: [ 3 ]


In  Barrett's esophagus , features that are classified as atypia but not as  dysplasia  are mainly: [ 5 ]


It may or may not be a  precancerous  indication associated with later  malignancy , but the level of appropriate concern is highly dependent on the context with which it is diagnosed.


For example, already differentiated, specialised cells such as epithelia displaying "cellular atypia" are far less likely to become problematic (cancerous/malignant) than are  myeloid progenitor cells  of the immune system. The 'further back' in an already specialised, differentiated cell's lineage, the more problematic cellular atypia is likely to be. This is due to the conferring of such atypia to progeny-cells further down the lineage of that cell type.


In  medicine ,  Breslow's depth  was used as a  prognostic factor  in  melanoma  of the  skin . It is a description of how deeply tumor cells have invaded. Currently, the standard Breslow's depth has been replaced by the AJCC depth, in the  AJCC staging system of melanoma . Originally, Breslow's depth was divided into 5 stages. [ 1 ]


Depth of invasion was first reported as a prognostic factor in melanoma by the  pathologist  Alexander Breslow, M.D. at George Washington University in 1970. [ 1 ]  In recognition of his contribution, the depth of invasion of melanoma is referred to by the  eponym   Breslow's depth .


Subsequent studies confirmed and refined the role of depth of invasion in the prognosis of malignant melanoma. [ 2 ] [ 3 ]  Currently, Breslow's depth is included in the  AJCC   staging  guidelines for melanoma as a major prognostic factor.


Tumor depth is most accurately measured by evaluating the entire tumor via an  excisional biopsy . Determination from specimens obtained using other  biopsy  techniques, such as a wedge or punch biopsy, are less accurate. Tumor depth cannot be calculated from a shave biopsy that only contains a portion of the tumor because it leads to an underestimation of its thickness.


Breslow's depth is determined by using an  ocular micrometer  at a  right angle  to the skin to directly measure the depth to which  tumor cells  have invaded the  skin . Breslow's depth is measured from the  granular layer  of the  epidermis  down to the deepest point of invasion (sometimes involving detached nests of cells).


Tumor depth is one of the cornerstones of the current  AJCC   TNM staging  of malignant melanoma. A large study validated the importance of tumor depth (but not Breslow's original description) as one of the three most important prognostic factors in melanoma (the others being T stage and ulceration). [ 4 ]  Breslow's depth also accurately predicted the risk for  lymph node   metastasis , with deeper tumors being more likely to involve the nodes. [ 5 ]


The above studies showed that depth was a continuous variable correlating with prognosis. However, for staging purposes, the most recent AJCC guidelines use cutoffs of 1 mm, 2 mm, and 4 mm to divide patients into stages.


Survival figures from British Association of Dermatologist Guidelines, 2002


Clark's level  is a related  staging system , used in conjunction with Breslow's depth, which describes the level of anatomical invasion of the melanoma in the skin. [ 6 ]  Clark's level was the primary factor in earlier AJCC staging schemas for melanoma.  [ citation needed ]  However, with further study, it has been shown that Clark's level has a lower predictive value, is less reproducible, and is more operator-dependent as compared with Breslow's depth.  [ citation needed ]  Thus, in the current (2010) AJCC staging system, Clark's level has prognostic significance only in patients with very thin (Breslow depth <1 mm) melanomas. [ 4 ]


Five anatomical levels are recognized, and higher levels have worsening prognostic implications. These levels are:


A  bruise , also known as a  contusion , is a type of  hematoma  of  tissue , [ 3 ]  the most common cause being  capillaries  damaged by  trauma , causing localized bleeding that  extravasates  into the surrounding  interstitial  tissues. Most bruises occur close enough to the epidermis such that the bleeding causes a visible discoloration. The bruise then remains visible until the blood is either absorbed by tissues or cleared by  immune system  action. Bruises which do not  blanch  under pressure can involve capillaries at the level of skin,  subcutaneous tissue , muscle, or bone. [ 4 ] [ 5 ]


Bruises are not to be confused with other similar-looking  lesions . Such lesions include  petechia  (less than 3 mm (0.12 in), resulting from numerous and diverse etiologies such as adverse reactions from medications such as warfarin, straining, asphyxiation,  platelet  disorders and diseases such as  cytomegalovirus ); [ 6 ]  and  purpura  (3–10 mm (0.12–0.39 in)), classified as palpable purpura or non-palpable purpura and indicating various pathologic conditions such as  thrombocytopenia . [ 7 ]  Additionally, although many  terminology  schemas treat an  ecchymosis  (plural, ecchymoses) (over 1 cm (0.39 in)) as synonymous with a bruise, [ 1 ]  in some other schemas, an ecchymosis is differentiated by its remoteness from the source and cause of bleeding, with blood dissecting through tissue planes and settling in an area remote from the site of trauma or even nontraumatic pathology, such as in  periorbital  ecchymosis (" raccoon eyes "), arising from a  basilar skull fracture  or from a  neuroblastoma . [ 8 ]


As a type of hematoma, a bruise is always caused by internal bleeding into the interstitial tissues which does not break through the skin, usually initiated by  blunt trauma , which causes damage through  physical compression  and  deceleration  forces. Trauma sufficient to cause bruising can occur from a wide variety of situations including accidents, falls, and surgeries. Disease states such as insufficient or malfunctioning  platelets , other  coagulation  deficiencies, or vascular disorders, such as venous blockage associated with severe  allergies [ 9 ]  can lead to the formation of purpura which is not to be confused with trauma-related bruising/contusion. [ 10 ]  If the trauma is sufficient to break the skin and allow blood to escape the interstitial tissues, the injury is not a bruise but bleeding, a different variety of hemorrhage. Such injuries may be accompanied by bruising elsewhere. [ 11 ]


Bruises often induce pain immediately after the trauma that results in their formation, but small bruises are not normally dangerous alone. Sometimes bruises can be serious, leading to other more life-threatening forms of hematoma, such as when associated with serious injuries, including  fractures  and more severe  internal bleeding .  The likelihood and severity of bruising depends on many factors, including type and healthiness of affected tissues. Minor bruises may be easily recognized in people with light skin color by characteristic blue or purple appearance (idiomatically described as "black and blue") in the days following the injury.


Hematomas can be subdivided by size. By definition, ecchymoses are 1 centimetres in size or larger, and are therefore larger than  petechiae  (less than 3 millimetres in diameter) [ 12 ]  or  purpura  (3 to 10 millimetres in diameter). [ 13 ]  Ecchymoses also have a more diffuse border than other purpura. [ 14 ]  A broader definition of ecchymosis is the escape of blood into the tissues from ruptured blood vessels. [ 15 ] [ 16 ]  The term also applies to the subcutaneous discoloration resulting from seepage of blood within the injured tissue.


Bruise colors vary from red, blue, or almost black, depending on the severity of broken capillaries or blood vessels within the bruise site. Broken  venules  or  arterioles  often result in a deep blue or dark red bruise, respectively. Darker colored bruises may result from a more severe bleeding from both blood vessels. Older bruises may appear yellow, green or brown. [ 11 ] [ 17 ]


There are many causes of subcutaneous hematomas including ecchymoses.  Coagulopathies  such as  hemophilia A  may cause ecchymosis formation in children. [ 18 ]  The medication  betamethasone  can have the adverse effect of causing ecchymosis. [ 19 ]


The presence of bruises may be seen in patients with  platelet  or  coagulation  disorders, or those who are being treated with an  anticoagulant . Unexplained bruising may be a warning sign of  child abuse ,  domestic abuse , or serious medical problems such as  leukemia  or  meningoccocal  infection. Unexplained bruising can also indicate internal bleeding or certain types of cancer. Long-term glucocorticoid therapy can cause easy bruising. Bruising present around the  navel  (belly button) with severe abdominal pain suggests acute  pancreatitis . Connective tissue disorders such as  Ehlers–Danlos syndrome  may cause relatively easy or spontaneous bruising depending on the severity. Spontaneous bruising or bruising with minimal trauma in the absence of other explanations and together with other minor or major criteria suggestive of vascular Ehlers–Danlos Syndrome (vEDS) suggests  genetic testing  for the condition. [ 20 ]


During an  autopsy , bruises accompanying  abrasions  indicate the abrasions occurred while the individual was alive, as opposed to damage incurred post mortem.


Bruise shapes may correspond directly to the instrument of injury or be modified by additional factors. Bruises often become more prominent as time lapses, resulting in additional size and swelling, and may grow to a large size over the course of the hours after the injury that caused the bruise was inflicted.


Bruises can be scored on a scale from 0–5 to categorize the severity and danger of the injury.


The harm score is determined by the extent and severity of the injuries to the organs and tissues causing the bruising, in turn depending on multiple factors.  For example, a  contracted  muscle will bruise more severely, as will tissues crushed against underlying bone.   Capillaries  vary in strength, stiffness and toughness, which can also vary by age and medical conditions.


Low levels of damaging forces produce small bruises and generally cause the individual to feel minor pain straight away. Repeated impacts worsen bruises, increasing the harm level. Normally, light bruises heal nearly completely within two weeks, although duration is affected by variation in severity and individual healing processes; [ 22 ]  generally, more severe or deeper bruises take somewhat longer.


Severe bruising (harm score 2–3) may be dangerous or cause serious complications.  Further bleeding and excess fluid may accumulate causing a hard, fluctuating lump or swelling hematoma.  This has the potential to cause  compartment syndrome  in which the swelling cuts off blood flow to the tissues.  The trauma that induced the bruise may also have caused other severe and potentially fatal harm to internal  organs .  For example, impacts to the head can cause  traumatic brain injury : bleeding, bruising and massive swelling of the brain with the potential to cause  concussion ,  coma  and death.  Treatment for brain bruising may involve emergency surgery to relieve the pressure on the brain.


Damage that causes bruising can also cause bones to be  broken ,  tendons  or muscles to be  strained ,  ligaments  to be  sprained , or other tissue to be damaged.  The symptoms and signs of these injuries may initially appear to be those of simple bruising. Abdominal bruising or severe injuries that cause difficulty in moving a limb or the feeling of liquid under the skin may indicate life-threatening injury and require the attention of a physician.


Increased distress to tissue causes  capillaries  to break under the skin, allowing blood to escape and build up. As time progresses, blood seeps into the surrounding tissues, causing the bruise to darken and spread.  Nerve  endings within the affected tissue detect the increased pressure, which, depending on severity and location, may be perceived as pain or pressure or be  asymptomatic . The damaged capillary  endothelium  releases  endothelin , a  hormone  that causes  narrowing of the blood vessel  to minimize bleeding. As the endothelium is destroyed, the underlying  von Willebrand factor  is exposed and initiates  coagulation , which creates a temporary  clot  to plug the wound and eventually leads to restoration of normal tissue.


During this time, larger bruises may change color due to the breakdown of  hemoglobin  from within escaped  red blood cells  in the extracellular space. The striking colors of a bruise are caused by the  phagocytosis  and sequential degradation of hemoglobin to  biliverdin  to  bilirubin  to  hemosiderin , with hemoglobin itself producing a red-blue color, biliverdin producing a green color, bilirubin producing a yellow color, and hemosiderin producing a golden-brown color. [ 11 ]  As these products are cleared from the area, the bruise disappears. Often the underlying tissue damage has been repaired long before this process is complete.


Treatment for light bruises is minimal and may include  RICE  ( rest ,  ice ,  compression , and  elevation ),  painkillers  (particularly  NSAIDs ) and, later in recovery, light stretching exercises. Particularly, immediate application of ice while elevating the area may reduce or completely prevent swelling by restricting blood flow to the area and preventing internal bleeding. Rest and preventing re-injury is essential for rapid recovery.


Very gently massaging the area and applying heat may encourage blood flow and relieve pain according to the  Gate control theory  of pain, although causing additional pain may indicate the massage is exacerbating the injury. [ 23 ]  As for most injuries, these techniques should not be applied until at least three days following the initial damage to ensure all internal bleeding has stopped, because although increasing blood flow will allow more healing factors into the area and encourage drainage, if the injury is still bleeding this will allow more blood to seep out of the wound and cause the bruise to become worse.


Folk medicine , including ancient medicine of Egyptians, Greeks, Celts, Turks, Slavs, Maya, Aztecs and Chinese, has used bruising as a treatment for some health problems. The methods vary widely and include cupping, scraping, and slapping.  Fire cupping  uses suction which causes bruising in patients. Scraping ( gua sha ) uses a small hand device with a rounded edge to gently scrape the scalp or the skin. Another ancient device that creates mild bruising is a  strigil , used by Greeks and Romans in the bath. Archaeologically there is no precedent for scraping tools before Greek archaeological evidence, not Chinese or Egyptian. [ 24 ]


The word  ecchymosis  ( / ˌ ɛ k ɪ ˈ m oʊ s ɪ s / ; plural  ecchymoses ,  / ˌ ɛ k ɪ ˈ m oʊ s iː s / ), comes to English from  Neo-Latin , based on  Greek   ἐκχύμωσις ,  ekchymōsis , from  ἐκχυμοῦσθαι ,  ekchymousthai , 'to extravasate blood', from  ἐκ- ,  ek-  (elided to  ἐ- ,  e- ) and  χυμός ,  chymos , 'juice'. [ 25 ]  Compare  enchyma , "tissue infused with organic juice"; elaboration from chyme, the formative juice of tissues.


Clark's level  is a  staging system , which describes the level of anatomical invasion of the  melanoma  in the skin. It was developed by  Wallace H. Clark Jr.  at  Harvard University  and  Massachusetts General Hospital  in the 1960s.


Five anatomical levels are recognized, and higher levels have worsening prognostic implications.  These levels are: [ 1 ]


In the  United States , the current staging system adopted by the  American Joint Committee on Cancer  (AJCC) no longer considers Clark's level, because it is less prognostic and more subjective than other alternatives. [ 2 ]


However, it is a mandatory component for melanoma pathology in  Sweden . [ 3 ]


A  comedo  (plural  comedones ) is a clogged  hair follicle  (pore) in the skin. [ 2 ]   Keratin  (skin debris) combines with oil to block the follicle. [ 3 ]  A comedo can be open ( blackhead ) or closed by skin ( whitehead ) and occur with or without  acne . [ 3 ]  The word  comedo  comes from  Latin   comedere  'to eat up' and was historically used to describe parasitic worms; in modern medical terminology, it is used to suggest the worm-like appearance of the expressed material. [ 1 ]


The chronic inflammatory condition that usually includes comedones, inflamed papules, and pustules ( pimples ) is called acne. [ 3 ] [ 4 ]  Infection causes inflammation and the development of  pus . [ 2 ]  Whether a skin condition classifies as acne depends on the number of comedones and infection. [ 4 ]  Comedones should not be confused with  sebaceous filaments .


Comedo-type  ductal carcinoma  in situ  (DCIS) is not related to the skin conditions discussed here. DCIS is a noninvasive form of breast cancer, but comedo-type DCIS may be more aggressive, so may be more likely to become invasive. [ 5 ]


Oil production in the  sebaceous glands  increases during puberty, causing comedones and  acne  to be common in adolescents. [ 3 ] [ 4 ]  Acne is also found premenstrually and in women with  polycystic ovarian syndrome . [ 3 ]  Smoking may worsen acne. [ 3 ]


Oxidation  rather than poor hygiene or dirt causes blackheads to be black. [ 2 ]  Washing or scrubbing the skin too much could make it worse, by irritating the skin. [ 2 ]  Touching and picking at comedones might cause irritation and spread infection. [ 2 ]  What effect shaving has on the development of comedones or acne is unclear. [ 2 ]


Some skin products might increase comedones by blocking pores, [ 2 ]  and greasy hair products (such as  pomades ) can worsen acne. [ 3 ]  Skin products that claim to not clog pores may be labeled  noncomedogenic  or nonacnegenic. [ 6 ]  Make-up and skin products that are oil-free and water-based may be less likely to cause acne. [ 6 ]  Whether dietary factors or sun exposure make comedones better, worse, or neither is unknown. [ 3 ]


A hair that does not emerge normally, an  ingrown hair , can also block the pore and cause a bulge or lead to infection (causing inflammation and  pus ). [ 4 ]


Genes may play a role in the chances of developing acne. [ 3 ]  Comedones may be more common in some ethnic groups. [ 3 ] [ 7 ]  People of  Latino  and recent African descent may experience more inflammation in comedones, more comedonal acne, and earlier onset of inflammation. [ 3 ] [ 7 ]


Comedones are associated with the  pilosebaceous unit , which includes a  hair follicle  and  sebaceous gland . These units are mostly on the face, neck, upper chest, shoulders, and back. [ 3 ]  Excess keratin combined with  sebum  can plug the opening of the follicle. [ 3 ] [ 8 ]  This small plug is called a microcomedo. [ 8 ]   Androgens  increase sebum (oil) production. [ 3 ]  If sebum continues to build up behind the plug, it can enlarge and form a visible comedo. [ 8 ]


A comedo may be open to the air ("blackhead") or closed by skin ("whitehead"). [ 2 ]  Being open to the air causes oxidation of the melanin pigment, which turns it black. [ 9 ] [ 2 ]   Cutibacterium acnes  is the suspected infectious agent in acne. [ 3 ]  It can proliferate in sebum and cause inflamed  pustules  (pimples) characteristic of acne. [ 3 ]   Nodules  are inflamed, painful, deep bumps under the skin. [ 3 ]


Comedones that are 1 mm or larger are called macrocomedones. [ 10 ]  They are closed comedones and are more frequent on the face than neck. [ 11 ]


Solar comedones (sometimes called senile comedones) are related to many years of exposure to the sun, usually on the cheeks, not to acne-related pathophysiology. [ 12 ]


Using nonoily cleansers and mild soap may not cause as much irritation to the skin as regular soap. [ 13 ] [ 14 ]  Blackheads can be removed across an area with commercially available  pore-cleansing strips  (which can still damage the skin by leaving the pores wide open and ripping excess skin) or the more aggressive  cyanoacrylate  method used by dermatologists. [ 15 ]


Squeezing blackheads and whiteheads can remove them, but  can also damage the skin. [ 2 ]  Doing so increases the risk of causing or transmitting infection and scarring, as well as potentially pushing any infection deeper into the skin. [ 2 ]  Comedo extractors are used with careful hygiene in beauty salons and by dermatologists, usually after using steam or warm water. [ 2 ]


Complementary medicine  options for acne in general have not been shown to be effective in trials. [ 3 ]  These include aloe vera,  pyridoxine  (vitamin B 6 ), fruit-derived acids,  kampo  (Japanese herbal medicine),  ayurvedic  herbal treatments, and acupuncture. [ 3 ]


Some  acne treatments  target infection specifically, but some treatments are aimed at the formation of comedones, as well. [ 16 ]  Others remove the dead layers of the skin and may help clear blocked pores. [ 2 ] [ 3 ] [ 4 ]


Dermatologists  can often extract open comedones with minimal skin trauma, but closed comedones are more difficult. [ 3 ]  Laser treatment for acne might reduce comedones, [ 17 ]  but dermabrasion and laser therapy have also been known to cause scarring. [ 10 ]


Macrocomedones (1 mm or larger) can be removed by a dermatologist using surgical instruments or cauterized with a device that uses light. [ 10 ] [ 11 ]  The acne drug  isotretinoin  can cause severe flare-ups of macrocomedones, so dermatologists recommend removal before starting the drug and during treatment. [ 10 ] [ 11 ]


Some research suggests that the common acne medications  retinoids  and  azelaic acid  are beneficial and do not cause increased pigmentation of the skin. [ 18 ]  If using a retinoid, sunscreen is recommended.


Favre–Racouchot syndrome  occurs in sun-damaged skin and includes open and closed comedones. [ 19 ]


Nevus comedonicus  or comedo nevus is a benign  hamartoma  (birthmark) of the  pilosebaceous unit  around the oil-producing gland in the skin. [ 20 ]  It has widened open hair follicles with dark keratin plugs that resemble comedones, but they are not actually comedones. [ 20 ] [ 21 ]


Dowling–Degos disease  is a genetic pigment disorder that includes comedo-like  lesions  and scars. [ 22 ] [ 23 ]


Familial dyskeratotic comedones are a rare  autosomal-dominant  genetic condition, with keratotic (tough) papules and comedo-like lesions. [ 24 ] [ 25 ]


A  cyst   / s ɪ s t /  is a closed  sac , having a distinct envelope and  division  compared with the nearby  tissue . Hence, it is a cluster of  cells  that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble); however, the distinguishing aspect of a cyst is that the cells forming the "shell" of such a sac are distinctly abnormal (in both appearance and behaviour) when compared with all surrounding cells for that given location. A cyst may contain air, fluids, or semi-solid material. A collection of  pus  is called an  abscess , not a cyst. Once formed, a cyst may resolve on its own. When a cyst fails to resolve, it may need to be removed  surgically , but that would depend upon its type and location.


Cancer -related cysts are formed as a defense mechanism for the body following the development of  mutations  that lead to an uncontrolled  cellular division . Once that mutation has occurred, the affected cells divide incessantly and become cancerous, forming a  tumor . The body encapsulates those cells to try to prevent them from continuing their division and contain the tumor, which becomes known as a cyst. That said, the cancerous cells still may mutate further and gain the ability to form their own  blood vessels , from which they receive nourishment before being contained. Once that happens, the capsule becomes useless, and the tumor may advance from  benign  to cancerous.


Some cysts are  neoplastic , and thus are called  cystic tumors . Many types of cysts are not neoplastic, they are  dysplastic  or  metaplastic .  Pseudocysts  are similar to cysts in that they have a sac filled with fluid, but lack an  epithelial  lining.


A  pseudocyst  is very similar to a cyst, but is a collection of cells without a distinct membrane ( epithelial  or  endothelial  cells).


A  syrinx  in the  spinal cord  or  brainstem  is sometimes inaccurately referred to as a "cyst".


Treatment ranges from simple  enucleation  of the cyst to  curettage  to  resection . There are cysts—e.g.,  buccal bifurcation cyst —that resolve on their own, in which just close observation may be employed, unless it is  infected  and  symptomatic . [ 15 ]


Despite being described in 1938 as "the  microscopic  appearance of cysts in the pancreas", [ 16 ]   cystic fibrosis  is an example of a  genetic disorder  whose name is related to fibrosis of the  cystic duct  (which serves the  gallbladder ) and does not involve cysts. [ 17 ]


This is just one example of how the Greek root  cyst- , which simply means a fluid-filled sac, also is found in medical terms that relate to the  urinary bladder  and the  gallbladder , neither of which involve cysts.


The Dermatology life Quality Index (DLQI)  is a ten-question questionnaire used to measure the impact of  skin disease  on the quality of life of an affected person.  It is designed for people aged 16 years and above.


The DLQI was created by Andrew Y Finlay and Gul Karim Khan from 1990 to 1994 at the Department of Dermatology,  University of Wales College of Medicine  (now Cardiff University), Cardiff, UK. [ 1 ]  120 patients with a variety of skin diseases completed a questionnaire that asked them to write down all of the ways that their skin disease affected their lives. 49 different ways were identified, and these were used as the basis of the questions of the DLQI. [ 2 ]


The DLQI was first presented at the  British Association of Dermatologists  annual meeting in July 1993 [ 3 ]  and described in an article published in 1994 in  Clinical and Experimental Dermatology . [ 4 ]  This article has become one of the most frequently cited articles in clinical dermatology. [ 5 ]  The DLQI is the most frequently used method for evaluating quality of life for patients with different skin conditions. [ 6 ]


There are 10 questions, covering the following topics: symptoms, embarrassment, shopping and home care, clothes, social and leisure, sport, work or study, close relationships, sex, treatment.  Each question refers to the impact of the skin disease on the patient’s life over the previous week. [ 7 ]


The DLQI has been translated into over 140 languages. The full translations are available at the Cardiff University Department of Dermatology website. [ 8 ]


Each question is scored from 0 to 3, giving a possible score range from 0 (meaning no impact of skin disease on quality of life) to 30 (meaning maximum impact on quality of life).


A series of validated “band descriptors” were described in 2005 to give meaning to the scores of the DLQI. [ 9 ]


These bands are as follows: 0-1 = No effect on patient’s life, 2-5 = Small effect, 6-10 = Moderate effect, 11-20 = Very large effect, 21-30 = Extremely large effect.


The Minimal Clinically Important Difference (MCID) is the score difference that is the minimum meaningful difference for a patient. Although previously considered to be 5, [ 10 ]  the DLQI MCID for inflammatory skin diseases should be considered to be a score difference of 4. [ 11 ]


DLQI scores can be converted to EQ-5D utility values. [ 12 ]


The DLQI can provide clinicians with more accurate insight into the impairment of quality of life experienced by individual patients. This may lead to more appropriate clinical decisions. [ 13 ]   The DLQI can also be used when required by national guidelines, for example in the management of  psoriasis [ 14 ]  or hand eczema. [ 15 ]


The DLQI is recommended for use in national treatment guidelines, and to assist management decisions, [ 16 ]  in many countries, including: Australia, [ 17 ]  Canada, [ 18 ]  Bulgaria, [ 19 ]  Croatia, [ 19 ]  Czech Republic, [ 19 ]  England and Wales, [ 20 ]  Europe, [ 21 ]  Germany, [ 22 ]  Hungary, [ 19 ]  Italy, [ 23 ]  Japan,  [ 24 ]  Norway, [ 25 ]  Poland, [ 19 ]  Romania, [ 19 ]  Saudi Arabia, [ 26 ]  Scotland, [ 27 ]  Singapore, [ 28 ]  South Africa, [ 29 ]  Spain, [ 30 ]  Sweden, [ 31 ]   Switzerland, [ 32 ]  Taiwan, [ 33 ]  Turkey [ 34 ]  and  Venezuela. [ 35 ]


The DLQI has been used as a patient reported outcome measure in many published clinical research studies. [ 36 ]   For example, it has been used to assess novel drugs, [ 37 ]  models of clinical care, in audit of clinical services and in assessment of teledermatology. [ 36 ]  The DLQI is the most widely used quality of life outcome measure in randomised controlled trials of therapies for psoriasis. [ 38 ]


The Rule of Tens is a concept to aid clinicians in making the diagnosis of “severe psoriasis”. [ 39 ]  It states that a patient is considered to have “severe psoriasis” if their  body surface area  affected is >10%, or if their Psoriasis Area and Severity Index (PASI) score is >10, or if the DLQI score is >10. [ 39 ]  The Rule of Tens has influenced national guidelines concerning the criteria to be fulfilled before starting a patient on  biological therapy . [ 14 ]


The DLQI is  copyrighted  but the originators allow it to be used for routine clinical purposes without seeking permission and without charge. [ 8 ]


The DLQI has been validated for use on tablets such as the iPad. [ 40 ]


Several systematic reviews have been carried out documenting the use of the DLQI.


The DLQI has been used as an outcome measure in 454 randomised controlled trials, involving 69 diseases and 43 countries. [ 41 ]   In 24 randomised control trials the DLQI was used as a primary outcome measure. [ 42 ]  The DLQI has been used as a benchmark in the validation of 101 quality of life instruments. [ 43 ]


A systematic review of 207 studies has described aspects of the validation of the DLQI. [ 44 ]   The 207 articles included 58,828 patients from >49 different countries and 41 diseases met the inclusion criteria. The DLQI demonstrated strong test–retest reliability; 43 studies confirmed good internal consistency, Twelve studies used anchors to assess change responsiveness with effect sizes from small to large, giving confidence that the DLQI responds appropriately to change. Forty-two studies tested known-groups validity, providing confidence in construct and use of the DLQI over many parameters, including disease severity, anxiety, depression, stigma, scarring, well-being, sexual function, disease location and duration.


A  dermatomycosis  is a  skin disease  caused by a  fungus . [ 1 ]


The most frequent form is  dermatophytosis  (ringworm, tinea).
Another example is cutaneous  candidiasis . These fungal infections impair superficial layers of the skin, hair and nails.


Dermatoscopy , also known as  dermoscopy [ 1 ]  or  epiluminescence microscopy , is the examination of  skin lesions  with a  dermatoscope . It is a tool similar to a camera to allow for inspection of skin lesions unobstructed by skin surface reflections. The  dermatoscope  consists of a magnifier, a light source (polarized or non-polarized), a transparent plate and sometimes a liquid medium between the instrument and the  skin . The dermatoscope is often handheld, although there are stationary cameras allowing the capture of whole body images in a single shot. When the images or video clips are digitally captured or processed, the instrument can be referred to as a  digital epiluminescence dermatoscope . The image is then analyzed automatically and given a score indicating how dangerous it is. This technique is useful to  dermatologists  and skin cancer practitioners in distinguishing benign from  malignant  (cancerous) lesions, especially in the diagnosis of  melanoma .


There are two main types of dermatoscopes, hand held portable and stationary mounted type.


A hand held dermatoscope is composed of a transilluminating light source and a magnifying optic (usually a 10-fold magnification). There are three main modes of dermatoscopy: [ 2 ]


Polarized light allows for visualization of deeper skin structures, while non-polarized light provide information about the superficial skin. Most modern dermatoscopes allow the physician to toggle between the two modes, which provide complementary information. Others may also allow the doctor to have different zoom levels and color overlay.


A stationary type allows a full body image to be captured in one snap. It is then transferred into image analysis algorithms that generates a three dimensional model of the person. Lesions on the person are marked and analyzed using  Artificial intelligence .


With doctors who are experts in dermatoscopy, the diagnostic accuracy for melanoma is significantly better than those who do not have any specialized training. [ 3 ]
Thus, there is considerable improvement in the   sensitivity  (detection of melanomas) as well as  specificity   (percentage of non-melanomas correctly diagnosed as benign), compared with naked eye examination. The accuracy by dermatoscopy was increased up to 20% in the case of sensitivity and up to 10% in the case of specificity, compared with naked eye examination. [ 4 ] [ 5 ]   By using dermatoscopy the specificity is thereby increased, reducing the frequency of unnecessary surgical excisions of benign lesions. [ 6 ] [ 7 ]


Artificial intelligence is used to automatically distinguish benign from malignant ( cancerous ) lesions. [ 25 ]  Modern software technology allows the usage of databases to aid in this process. [ 26 ] [ 27 ]  Patients will consent their lesion pictures to be stored in a database which acts as an archive and allow artificial intelligence programs to compare newly taken ones. The program then compares key features of a new image with known features of benign and malignant lesions. Oftentimes a score is given to a specific lesion, indicating how dangerous and likely it is to be a malignant lesion. It is then flagged for further examination through a  dermatologist . This speeds up the diagnosis process.


One limit is that since not many patients get their lesions documented, the sample size is minuscule compared to what an AI needs.


Proposed solutions include generating synthetic images of skin lesions to improve the algorithm. Then, the AI needs to differentiate whether the sample came from the synthetic samples or from real data sets. It needs to minimize the probability that it will predict its outputs as fake while also maximizing its probability to correctly distinguish between real and fake samples. [ 28 ]


Skin surface microscopy started in 1663 by Johan Christophorous Kolhaus and was improved with the addition of immersion oil in 1878 by  Ernst Abbe . [ 29 ]  The German dermatologist,  Johann Saphier , added a built-in light source to the instrument.  Leon Goldman  was the first dermatologist to coin the term "dermascopy" and to use the dermatoscope to evaluate pigmented cutaneous lesions.


In 1989 dermatologists from the  Ludwigs-Maximilian-University of Munich  developed a new device for dermoscopy. A team of physicians led by  Professor Otto Braun-Falco  in collaboration with the medical device manufacturer  HEINE Optotechnik  developed a dermatoscope, which was hand-held and illuminated by a halogen lamp. It also featured an achromatic lens with a 10-fold magnification. To reduce light reflection the lesion was covered with immersion oil. This dermatoscope helped to diagnose pigmented skin lesions more quickly and easily. The approach was confirmed by Wilhelm Stolz et al. from the Department of Dermatology and Allergology of the University of Munich and published in the "Lancet"(1989). [ 30 ]


At the  Medical University of Vienna  a dermatoscope based on cross-polarization was  invented and patented , a methodology further used in digital dermatoscopes such as the  MoleMax  device or by  FotoFinder . Following, in 2001, a California medical device manufacturer, 3Gen, introduced the first polarized handheld dermatoscope, the DermLite. Polarized illumination, coupled with a cross-polarised viewer, reduces (polarised) skin surface reflection, thus allowing visualisation of skin structures (the light from which is depolarised) without using an immersion fluid. Examination of several lesions is thus more convenient because physicians no longer have to stop and apply immersion oil, alcohol, or water to the skin before examining each lesion. With the marketing of polarised dermatoscopes, dermatoscopy increased in popularity among physicians worldwide. Although images produced by polarised light dermatoscopes are slightly different from those produced by a traditional skin contact glass dermatoscope, they have certain advantages, such as vascular patterns not being potentially missed through compression of the skin by a glass contact plate. [ 31 ]


Due to the fairly standardised imaging, and limited amount of diagnoses compared to clinical dermatology, dermatoscopic images became one center of interest for automated medical image analysis. While in the past decades computer vision algorithms and hardware-based method were used [ 32 ] [ 33 ]  large standardized public image collections such as HAM10000 [ 34 ]  enabled application of convolutional neural networks.
The latter approach has now shown experimental evidence of human-level accuracy in larger/international, [ 35 ] [ 36 ] [ 37 ]
 [ 38 ]  and smaller/local trials, [ 39 ] [ 40 ] [ 41 ]  but this application is not without dispute. [ 42 ] [ 43 ]


Full-body capture


Desquamation , or  peeling skin , is the shedding of dead cells from the outermost layer of  skin . [ 1 ]


The term is from  Latin    desquamare  'to scrape the  scales  off a  fish '.


Keratinocytes  are the predominant cells of the  epidermis , the outermost layer of the skin. Living keratinocytes reside in the basal, spinous, or granular layers of the epidermis. The outermost layer of the epidermis is called the  stratum corneum  and it is composed of terminally differentiated keratinocytes, the  corneocytes . In the absence of disease, desquamation occurs when corneocytes are individually shed unnoticeably from the surface of the skin. [ 2 ]  Typically the time it takes for a corneocyte to be formed and then shed is about 14 weeks but this time can vary depending on the anatomical location that the skin is covering. For example, desquamation occurs more slowly at acral (palm and sole) surfaces and more rapidly where the skin is thin, such as the eyelids. Normal desquamation can be visualized by immersing skin in warm or hot water. This induces the outermost layer of corneocytes to shed, such as is the case after a hot shower or bath. [ citation needed ]


Corneocytes are held together by corneodesmosomes. In order for desquamation to occur these corneodesmosome connections must be degraded. [ 2 ]  Keratinocytes residing in the stratum granulosum produce corneodesmosome-degrading kallikrein family members, especially  KLK1 ,  KLK5 , and  KLK7 . [ 3 ]  Kallikreins are serine proteases. They are packaged within lamellar bodies and released into the intercellular space between the keratinocytes as they transition into becoming corneocytes. [ 2 ]  To prevent premature desquamation, granular layer keratinocytes also produce kallikrein-inhibitory proteins. [ 3 ]  At acral surfaces, desquamation occurs more slowly because granular layer keratinocytes downregulate expression of KLK1 and KLK7 and upregulate expression of protease inhibitors, including the KLK5-specific  SPINK9  and the cysteine protease inhibitors CSTA and CST3. [ 3 ]  Slowing the process of corneocyte desquamation allows acral (palm and sole) skin to form a thick protective stratum corneum. [ 3 ]


Scale forms on the skin surface in various disease settings, and is the result of abnormal desquamation. In pathologic desquamation, such as that seen in X-linked ichthyosis, the stratum corneum becomes thicker (hyperkeratosis), imparting a "dry" or scaly appearance to the skin, and instead of detaching as single cells, corneocytes are shed in clusters, which forms visible scales. [ 2 ]  Desquamation of the  epidermis  may result from disease or  injury  of the skin. For example, once the  rash  of  measles  fades, there is desquamation. Skin peeling typically follows healing of a first degree  burn  or  sunburn .  Toxic shock syndrome , a potentially fatal  immune system  reaction to a  bacterial infection  such as  Staphylococcus aureus , [ 4 ]  can cause severe desquamation; so can  mercury poisoning . Other serious skin diseases involving extreme desquamation include  Stevens–Johnson syndrome  and  toxic epidermal necrolysis  (TEN). [ 5 ]  Radiation can cause dry or  moist desquamation . [ 6 ]  Desquamation is also abnormal in patients with immune-mediated skin diseases such as psoriasis and atopic dermatitis. [ 3 ]  Abnormal desquamation often results in scale formation on the skin's surface. [ 3 ]   Lipid composition alterations in scale have been used to construct diagnostic models for human skin disease. [ 3 ]


Certain eye tissues, including the  conjunctiva  and  cornea , may undergo pathological desquamation in diseases such as  dry eye syndrome . [ 7 ]  The anatomy of the  human eye  makes desquamation of the  lens  impossible. [ 8 ]


Dyskeratosis  is abnormal  keratinization  occurring prematurely within individual cells or groups of cells below the  stratum granulosum . [ 1 ]


Dyskeratosis congenita is  congenital  disease characterized by  reticular  skin pigmentation, nail degeneration, and  leukoplakia  on the  mucous membranes  associated with short  telomeres . [ 2 ]


Erythema  ( Ancient Greek :  ἐρύθημα , from  Greek    erythros  'red') is redness of the skin or  mucous membranes , caused by  hyperemia  (increased blood flow) in superficial  capillaries . [ 1 ]  It occurs with any skin injury, infection, or  inflammation . Examples of erythema not associated with pathology include  nervous blushes . [ 2 ]


It can be caused by  infection ,  massage , electrical treatment,  acne  medication,  allergies , exercise, solar radiation ( sunburn ),  photosensitization , [ 3 ]   acute radiation syndrome ,  mercury toxicity ,  blister agents , [ 4 ]   niacin  administration, [ 5 ]  or waxing and tweezing of the hairs—any of which can cause the affected capillaries to dilate, resulting in redness. Erythema is a common side effect of  radiotherapy  treatment due to patient exposure to  ionizing radiation .


Erythema disappears on finger pressure ( blanching ), whereas  purpura  or bleeding in the skin and  pigmentation  do not. There is no temperature elevation, unless it is associated with the dilation of arteries in the deeper layer of the skin. [ citation needed ]


Erythrism  or  erythrochroism  refers to an unusual reddish pigmentation of an animal's  hair ,  skin ,  feathers , or  eggshells . [ 1 ]


Causes of erythrism include:


Erythrism in  katydids  has been occasionally observed. The coloring might be a camouflage that helps some members of the species survive on red plants. [ 4 ]  There is also consensus that the erythristic mutation is actually a dominant trait among katydid species, albeit a disadvantageous one, due to the overwhelmingly green coloration of most foliage. Hence, most pink or otherwise vividly colored katydids do not survive to adulthood, and this observation explains their rarity. [ 5 ]  Erythrism in  leopards  is rare, but one study [ 6 ]  reported that two of twenty-eight leopards seen in  camera traps  in a South African nature reserve were erythristic, and the authors found records of five other "strawberry" leopards from the region. [ 7 ]


An  exanthem  is a widespread  rash  occurring on the outside of the body and usually occurring in  children . [ 1 ]  It is usually caused by a virus, [ 2 ]  but an exanthem can be caused by  bacteria , [ 3 ]   toxins ,  drugs , other  microorganisms , or as the result from  autoimmune disease . [ citation needed ]


The term exanthem is from the  Greek   ἐξάνθημα ,  exánthēma , 'a breaking out'. [ 4 ]  It can be contrasted with  enanthems  which occur inside the body, such as on mucous membranes.


In 1905, the Russian-French physician Léon Cheinisse (1871–1924), proposed a numbered classification of the six most common childhood exanthems. [ 5 ] [ 6 ] [ 7 ] [ 8 ] [ 9 ]


Of these six "classical" infectious childhood exanthems, [ 10 ]  four are viral. Numbers were provided in 1905. [ 11 ]


The four viral exanthems have much in common, and are often studied together as a class. They are:


Scarlet fever , or "second disease", is associated with the bacterium  Streptococcus pyogenes .  Fourth disease , also known as "Dukes' disease" is a condition whose existence is not widely accepted today. It was described in 1900 and is postulated to be related to the bacterium  Staphylococcus aureus . [ 3 ]


In 1979 and 2001 a possible "seventh disease" was postulated following reports of a condition in Japan also referred to as acute febrile infantile  mucocutaneous lymph node syndrome  (MCLS). [ 14 ]


Many other common viruses apart from the ones mentioned above can also produce an exanthem as part of their presentation, though they are not considered part of the classic numbered list:


The  Ferriman–Gallwey score  is a method of evaluating and quantifying  hirsutism  in women.  The method was originally published in 1961 by D. Ferriman and J.D. Gallwey in the  Journal of Clinical Endocrinology . [ 1 ]


The original method used 11 body areas to assess hair growth, but was decreased to 9 body areas in the modified method:


In the modified method, hair growth is rated from 0 (no growth of  terminal hair ) to 4 (extensive hair growth) in each of the nine locations.  A patient's score may therefore range from a minimum score of 0 to a maximum score of 36. With each ethnic group, the amount of hair expected for that ethnicity should be considered. For example, in  Caucasian  women, a score of 8 or higher is regarded as indicative of  androgen  excess.


The method was further modified in 2001 to include a total of 19 locations, with the 10 extra locations being:  sideburns ,  neck ,  buttocks ,  inguinal  area,  perianal  area,  forearm ,  leg ,  foot ,  toes  and  fingers .  Each area has its own specified definition of the four-point scale. [ 2 ]


In  medicine , a  finger tip unit  ( FTU ) is defined as the amount of  ointment ,  cream  or other semi-solid  dosage form  expressed from a tube with a 5 mm diameter nozzle, applied from the distal skin-crease to the tip of the  index finger  of an adult. [ 1 ] [ 2 ]    The "distal skin-crease" is the skin crease over the joint nearest the end of the finger.  One FTU is enough to treat an area of skin twice the size of the flat of an adult's hand with the fingers together, i.e. a "handprint".  Two FTUs are approximately equivalent to 1 g of topical  steroid .


One handprint is 0.8% (i.e. approximately 1%) of the total body surface area, [ 3 ]  and one FTU covers approximately two handprints. As two FTUs are approximately equivalent to 1g of topical application, the "Rule of Hand" states that "4 hand areas = 2 FTU = 1 g". [ 4 ]


In the original study in the UK, [ 1 ]  one FTU weighed 0.49 g in men and 0.43 g in women.  The area covered by one FTU was 312 cm 2  in men and 257 cm 2  in women. [ 2 ]  Very similar results were found in a Mexico study. [ 5 ]  The weight of an FTU has been recalculated in Japan, relating to the use of 5 g tubes of ointment with a much smaller nozzle diameter. [ 6 ]   The weight of ointment is less if the nozzle diameter is smaller than the standard 5 mm.


When a topical drug was used as a foam, the weight of an FTU was 52.5 μg: the area covered by one foam FTU was less than that of an FTU of cream. [ 7 ]


The FTU is particularly useful when counseling patients with regards to the amount of topical steroid cream they should be applying in order to minimize the side-effects which are associated with their use. The FTU can also be used in children. [ 8 ]


The FTU concept has been used as a central part of an education programme for parents of children with atopic eczema. [ 9 ]


The use of the FTU has been advocated to reduce the variation in usage of topical steroids  [ 10 ]  and to encourage adherence to therapy. [ 11 ]   The FTU can also be used to guide the use of topical sunscreens. [ 12 ]


Dermatology Working Groups in the UK  [ 13 ]  and in Poland  [ 14 ]  have recommended that guidance for use of topical corticosteroids in patient information leaflets should include clear FTU instructions, preferably with images of a FTU and a chart to show the number of units required for specific areas of the body.  USA guidelines of care  [ 15 ]  for the management of psoriasis with topical therapies include guidance of amount to be used based on the FTU.


European Guidelines for the treatment of atopic eczema recommend that application amount of topical anti-inflammatory therapy should follow the FTU rule. [ 16 ]    In the USA it has been recommended that the FTU should be used as part of the treatment plan and communication with patients and caregivers of children with atopic eczema. [ 17 ]


The FTU has been used to standardize the amount of cream being applied in clinical research studies in the UK, [ 18 ]  Belgium, [ 19 ]  Turkey, [ 20 ]  India, [ 21 ]  Iran, [ 22 ]  Pakistan, [ 23 ]  Malaysia, [ 24 ]  and the USA. [ 25 ] [ 26 ]


The  Fitzpatrick scale  (also  Fitzpatrick skin typing test ; or  Fitzpatrick phototyping scale ) is a numerical classification schema for  human skin color . It was developed in 1975 by American dermatologist  Thomas B. Fitzpatrick  as a way to estimate the response of different types of skin to  ultraviolet  (UV) light. [ 2 ]  It was initially developed on the basis of skin color to measure the correct dose of  UVA  for  PUVA therapy , and when the initial testing based only on hair and eye color resulted in too high UVA doses for some, it was altered to be based on the patient's reports of how their skin responds to the sun; it was also extended to a wider range of skin types. [ 3 ] [ 4 ] [ 5 ]  The Fitzpatrick scale remains a recognized tool for dermatological research into human skin pigmentation.


The following table shows the six categories of the Fitzpatrick scale in relation to the 36 categories of the older  von Luschan scale : [ 6 ] [ 7 ] [ 8 ]


The Fitzpatrick scale is also the basis of skin color in  emoji , with five modifiers according to the Fitzpatrick scale (types  I  and  II  merged).


The Fitzpatrick scale has been criticized for its  Eurocentric bias  and insufficient representation of global skin color diversity. [ 9 ]  The scale originally was developed for classifying " white skin " in response to  solar radiation , [ 2 ]  and initially included only four categories focused on white skin, with "brown" and "black" skin types (V and VI) added as an afterthought. [ 3 ]


The scale's methodology, relying on self-reporting of skin color,  sunburn , and  sun tanning  response, fails to capture the broad spectrum of skin reflectance. Studies demonstrate that European populations have the narrowest skin color variation, whereas groups categorized as 'brown' or 'black' exhibit a much wider range. [ 10 ] [ 11 ]


The efficacy of the Fitzpatrick scale even among white-skinned individuals has been argued to be questionable, [ 9 ]  since studies such as that on a Dutch student population [ 12 ]  have found it inadequate for categorizing, challenging its appropriateness for investigating the relationship between sunburn tendency and tanning ability. [ 9 ]


The Fitzpatrick scale's Eurocentric orientation and its limitations in accurately representing global skin color diversity, along with similar biases in classifying other phenotypic traits, have been argued to require more inclusive and scientifically valid categorizations in dermatological and genetic research. [ 9 ]


A  fungating lesion  is a  skin lesion  that  fungates , that is, becomes like a  fungus  in its appearance or growth rate. It is marked by  ulcerations  (breaks on the skin or surface of an organ) and  necrosis  (death of living tissue) and usually presents a foul odor. This kind of lesion may occur in many types of  cancer , including  breast cancer ,  melanoma , and  squamous cell carcinoma , and especially in advanced disease. The characteristic malodorous smell is caused by  dimethyl trisulfide . [ 1 ]  It is usually not a  fungal infection  but rather a  neoplastic growth  with necrosing portions.


There is a weak evidence that  6%  miltefosine  solution applied topically on superficial fungating breast lesions of less than 1 cm in size, on patients who received previous radiotherapy, surgery, hormonal therapy or chemotherapy for their breast cancer, may slow the disease progression. [ 2 ]


This article incorporates  public domain material  from  Dictionary of Cancer Terms .  U.S. National Cancer Institute .


This  oncology  article is a  stub . You can help Wikipedia by  expanding it .


Glabrousness  (from the  Latin   glaber  meaning "bald", "hairless", "shaved", "smooth") is the technical term for a lack of  hair ,  down ,  setae ,  trichomes  or other such covering. A glabrous surface may be a natural characteristic of all or part of a plant or animal, or be due to loss because of a physical condition, such as  alopecia universalis  in humans, which causes hair to fall out or not regrow.


Glabrousness or otherwise, of leaves, stems, and fruit is a feature commonly mentioned in plant  keys ; in  botany  and  mycology , a  glabrous   morphological  feature is one that is smooth and may be glossy. It has no bristles or hair-like structures such as  trichomes . In anything like the zoological sense, no plants or fungi have hair or wool, although some structures may resemble such materials.


The term "glabrous" strictly applies only to features that lack  trichomes  at all times. When an organ bears trichomes at first, but loses them with age, the term used is  glabrescent .


In the model plant  Arabidopsis thaliana , trichome formation is initiated by the GLABROUS1 protein.  Knockouts  of the corresponding gene lead to glabrous plants. This  phenotype  has already been used in  gene editing  experiments and might be of interest as a visual marker for plant research to improve gene editing methods such as  CRISPR/Cas9. [ 1 ] [ 2 ]


In varying degrees most  mammals  have some  skin  areas without natural hair. In  humans , glabrous skin is found on the  ventral  portion of the  fingers ,  palms ,  soles of feet  and  lips , which are all parts of the body most closely associated with interacting with the world around us, [ 3 ]   as are the  labia minora  and  glans penis . [ 4 ]  There are four main types of  mechanoreceptors  in the glabrous skin of humans:  Pacinian corpuscles ,  Meissner's corpuscles ,  Merkel's discs , and  Ruffini corpuscles .


The  Naked mole-rat  ( Heterocephalus glaber ) has evolved skin lacking in general, pelagic hair covering, yet has retained long, very sparsely scattered tactile hairs over its body. [ 3 ]  Glabrousness is a trait that may be associated with  neoteny . [ citation needed ]


Within  entomology , the term glabrous is used to refer to those parts of an insect's body with are lacking in setae (bristles) or  scales . [ 5 ]


A  hydrocarbon keratosis , also known as  pitch keratosis ,  tar keratosis , and  tar wart , is a  precancerous   keratotic   skin lesion  that occurs in people who have been occupationally exposed to  polycyclic aromatic hydrocarbons . [ 1 ] : 728


Hydropic swelling  is intracellular  edema  of  keratinocytes , often seen with  viral infections . [ 1 ]


Hyperkeratinization  ( American English  or hyperkeratinisation in  British ) is a  disorder  of the cells lining the inside of a  hair follicle . It is the normal function of these cells to detach or slough off ( desquamate ) from the skin lining at normal intervals. The dead cells are then forced out of the follicle (primarily by the growing hair). However, in hyperkeratinization, this process is interrupted and a number of these dead skin cells do not leave the follicle because of an excess of  keratin , a natural protein found in the skin.  This excess of keratin, which is influenced by genetics, results in an increased adherence/bonding of dead skin cells together.  This cohesion of cells will block or "cap" the hair follicle (leading to  keratosis pilaris ) or clog the  sebaceous /oil duct (leading to  acne ).  Pathogens may also play a role in causing, perpetuating, or simply taking advantage of this phenomenon, such as virulent sub-strains of  Cutibacterium acnes  and irregular migration of  Staphylococcus epidermidis  from the outer surface of the skin into the follicle, where  commensal  strains of  C. acnes  exclusively habitate. It itches mildly at times, and strongly at others. Very often it cannot be felt at all. [ 1 ] [ 2 ]


Hyperkeratosis  is thickening of the  stratum corneum  (the outermost layer of the  epidermis , or  skin ), often associated with the presence of an abnormal quantity of  keratin , [ 1 ]  and is usually accompanied by an increase in the granular layer. As the corneum layer normally varies greatly in thickness in different sites, some experience is needed to assess minor degrees of hyperkeratosis.


It can be caused by  vitamin A deficiency  or chronic exposure to  arsenic .


Hyperkeratosis can also be caused by  B-Raf  inhibitor drugs such as  Vemurafenib  and  Dabrafenib . [ 2 ]


It can be treated with  urea-containing creams , which dissolve the  intercellular matrix  of the cells of the stratum corneum, promoting  desquamation  of scaly skin, eventually resulting in softening of hyperkeratotic areas. [ 3 ]


Follicular hyperkeratosis, also known as  keratosis pilaris  (KP), is a skin condition characterized by excessive development of  keratin  in  hair follicles , resulting in rough, cone-shaped, elevated  papules . The openings are often closed with a white plug of encrusted  sebum . When called  phrynoderma,  the condition is associated with nutritional deficiency or malnourishment.


This condition has been shown in several small-scale studies to respond well to supplementation with vitamins and fats rich in  essential fatty acids .  Deficiencies  of  vitamin E , [ 4 ]   vitamin A , and  B-complex vitamins  have been implicated in causing the condition. [ 5 ]  Follicular hyperkeratosis is also a symptom in inherited collagen-related diseases of  Ehlers-Danlos syndromes  and  Bethlem myopathy .


The term hyperkeratosis is often used in connection with lesions of the  mucous membranes , such as  leukoplakia . Because of the differences between mucous membranes and the skin (e.g., keratinizing mucosa does not have a  stratum lucidum  and non keratinizing mucosa does not have this layer or normally a  stratum corneum  or a  stratum granulosum ), sometimes specialized texts give slightly different definitions of hyperkeratosis in the context of mucosae. Examples are "an excessive formation of keratin (e.g., as seen in leukoplakia)" [ 12 ]  and "an increase in the thickness of the keratin layer of the epithelium, or the presence of such a layer in a site where none would normally be expected." [ 13 ]


The word  hyperkeratosis  ( / ˌ h aɪ p ər ˌ k ɛr ə ˈ t oʊ s ɪ s / ) is based on the  Ancient Greek morphemes   hyper-  +  kerato-  +  -osis , meaning 'the condition of too much keratin'.


Nasodigitic hyperkeratosis in dogs may be idiopathic, secondary to an underlying disease, or due to congenital abnormalities in the normal anatomy of the nose and fingertips.


In the case of congenital anatomical abnormalities, contact between the affected area and rubbing surfaces is impaired. It is roughly the same with finger pads — in animals with an anatomical abnormality, part of the pad is not in contact with rubbing surfaces and excessive keratin deposition is formed. The idiopathic form of nasodigitic hyperkeratosis in dogs develops from unknown causes and is more common in older animals (senile form). [ 14 ] [ 15 ]  Of all dog breeds, Labradors, Golden Retrievers, Cocker Spaniels, Irish Terriers, Bordeaux Dogs are the most prone to hyperkeratosis. [ 16 ]


Since the deposition of excess keratin cannot be stopped, therapy is aimed at softening and removing it. For moderate to severe cases, the affected areas should be hydrated (moisturised) with warm water or compresses for 5-10 minutes. Softening preparations are then applied once a day until the excess keratin is removed.


In dogs with severe hyperkeratosis and a significant excess of keratin, it is removed with scissors or a blade. After proper instructions, pet owners are able to perform this procedure at home, and it may be the only method of correction. [ 17 ]


Hyperpigmentation  is the darkening of an area of  skin  or  nails  caused by increased  melanin .


Hyperpigmentation can be caused by sun damage,  inflammation , or other skin injuries, including those related to  acne vulgaris . [ 1 ] [ 2 ] [ 3 ] : 854   People with darker skin tones are more prone to hyperpigmentation, especially with excess sun exposure. [ 4 ]


Many forms of hyperpigmentation are caused by an excess production of melanin. [ 4 ]  Hyperpigmentation can be diffuse or focal, affecting such areas as the face and the back of the hands. Melanin is produced by  melanocytes  at the lower layer of the  epidermis . Melanin is a class of pigment responsible for producing color in the body in places such as the eyes, skin, and hair. The process of melanin synthesis (melanogenesis) starts with the oxidation of  l -tyrosine to  l-dopa  by the enzyme  tyrosine hydroxylase , then to  l -dopaquinone  and  dopachrome , which forms melanin. [ 5 ]


As the body ages, melanocyte distribution becomes less diffuse and its regulation less controlled by the body. UV light stimulates melanocyte activity, and where concentration of the cells is greater, hyperpigmentation occurs. Another form of hyperpigmentation is post-inflammatory hyperpigmentation. These are dark and discoloured spots that appear on the skin following acne that has healed. [ 6 ]


Hyperpigmentation is associated with a number of diseases or conditions, including the following:


Hyperpigmentation can sometimes be induced by  dermatological   laser  procedures.


There are a wide range of depigmenting treatments used for hyperpigmentation conditions, and responses to most are variable. [ 11 ]


Most often treatment of hyperpigmentation caused by melanin overproduction (such as melasma, acne scarring, liver spots) includes the use of topical depigmenting agents, which vary in their efficacy and safety, as well as in prescription rules. [ 12 ]


Many topical treatments disrupt the synthesis of melanin by inhibiting the enzyme  tyrosine hydroxylase . [ 5 ]


Several are prescription only in the US, especially in high doses, such as  hydroquinone ,  azelaic acid , [ 13 ]  and  kojic acid . [ 14 ]  Some are available without prescription, such as  niacinamide , [ 15 ] [ 16 ]   l - ascorbic acid , [ citation needed ]  retinoids such as  tretinoin , [ 17 ]  or  cysteamine hydrochloride . [ 18 ] [ 19 ]  Hydroquinone was the most commonly prescribed hyperpigmentation treatment before the long-term safety concerns were raised, [ 20 ]  and the use of it became more regulated in several countries and discouraged in general by  WHO . [ 21 ]  For the US, only 2% is at present sold over-the-counter, and 4% needs prescription. In the EU hydroquinone was banned from cosmetic applications. [ 22 ]


Oral medication with  procyanidin  plus vitamins A, C, and E also shows promise as safe and effective for epidermal melasma. In an 8-week randomized, double-blind, placebo-controlled trial in 56 Filipino women, treatment was associated with significant improvements in the left and right malar regions, and was safe and well tolerated. [ 23 ]  Other treatments that do not involve topical agents are also available, including fraction lasers [ 24 ]  and dermabrasion. [ 12 ]


Laser toning using  YAG  lasers [ 25 ]  and  intense pulsed light  have been used to treat hyperpigmentation such as melasma and post-inflammatory hyperpigmentation. [ 26 ]


Hypopigmentation  is characterized specifically as an area of  skin  becoming lighter than the baseline skin color, but not completely devoid of  pigment . This is not to be confused with  depigmentation , which is characterized as the absence of all pigment. [ 1 ]   It is caused by  melanocyte  or  melanin  depletion, or a decrease in the  amino acid   tyrosine , which is used by melanocytes to make melanin. [ 2 ]  Some common genetic causes include mutations in the  tyrosinase  gene or  OCA2  gene. [ 3 ] [ 4 ]   As melanin pigments tend to be in the skin, eye, and hair, these are the commonly affected areas in those with hypopigmentation. [ 2 ]


Hypopigmentation is common and approximately one in twenty have at least one hypopigmented macule. Hypopigmentation can be upsetting to some, especially those with darker skin whose hypopigmentation marks are seen more visibly. Most causes of hypopigmentation are not serious and can be easily treated. [ 5 ]


It is seen in:


Areas of lighter pigmentation can be indications of hypopigmentation. Biopsies and genetic information are also used to diagnose.


Often, hypopigmentation can be brought on by laser treatments; however, the hypopigmentation can be treated with other lasers or light sources. [ 6 ]   Micropigmentation  can also be used to obtain a more normal appearance of the hypopigmentated skin. [ 7 ]


Treatment for hypopigmentation depends on the initial cause of the discoloration. [ medical citation needed ]


Can also use oral medications, such as oral imidazoles or triazoles.


Patients can also have transplants if they are stable or a depigmentation with topical MBEH if the patient has widespread discoloration.


Intertrigo , commonly called “skin fold dermatitis”, refers to a type of  inflammatory   rash  ( dermatitis ) of the superficial skin that occurs within a person's body folds. [ 1 ]  These areas are more susceptible to irritation and subsequent infection due to factors that promote skin breakdown such as moisture, friction, and exposure to bodily secretions and excreta such as  sweat ,  urine , or  feces . [ 1 ]  Areas of the body which are more likely to be affected by intertrigo include the  inframammary fold ,  intergluteal cleft ,  armpits , and spaces between the fingers or toes. Skin affected by intertrigo is more prone to infection than intact skin. [ 1 ]


The term "intertrigo" commonly refers to a secondary infection with  bacteria  (such as  Corynebacterium minutissimum ),  fungi  (such as  Candida albicans ), or  viruses . A frequent manifestation is  candidal intertrigo .


Intertrigo occurs more often in warm and humid conditions. Generally, intertrigo is more common in people with a weakened immune system including children, the elderly, and  immunocompromised  people. [ 1 ]  The condition is also more common in people who experience  urinary incontinence  and decreased ability to move. [ 1 ]


Bacterial intertrigo can be caused by  Streptococci  and  Corynebacterium minutissimum . [ 1 ] [ 2 ]


Intertrigo can be diagnosed clinically by a medical professional after taking a thorough history and performing a detailed physical examination. Many other skin conditions can mimic intertrigo's appearance including  erythrasma ,  inverse psoriasis ,  scabies ,  pyoderma ,  atopic dermatitis ,  candidiasis ,  seborrheic dermatitis , and  fungal infections of the superficial skin  like  Tinea versicolor  or  Tinea corporis . [ 1 ]


Greases, oils, and barrier ointments  [ 3 ]  may help by protecting skin from moisture and from friction. [ 4 ]


Intertrigo is also a known symptom of  vitamin B6  deficiency. [ 5 ]


Kamino bodies  are eosinophilic globoids. [ 1 ]  Kamino bodies are commonly observed microscopically with the condition  spitz nevi , [ 2 ]   a  benign   melanocytic nevus , a type of  skin  lesion, affecting the  epidermis  and  dermis . [ 3 ]


This article related to  pathology  is a  stub . You can help Wikipedia by  expanding it .


Keratosis  (from  kerat-  +  -osis ) [ 1 ]  is a growth of  keratin  on the skin or on  mucous membranes  stemming from  keratinocytes , the prominent cell type in the  epidermis . More specifically, it can refer to:


Leucism  ( / ˈ l uː s ɪ z əm ,   - k ɪ z -/ ) [ 2 ] [ 3 ] [ 4 ]  is a wide variety of conditions that result in partial loss of  pigmentation  in an  animal —causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles, but not the eyes. [ 4 ]  It is occasionally spelled  leukism . Some genetic conditions that result in a "leucistic" appearance include  piebaldism ,  Waardenburg syndrome ,  vitiligo ,  Chédiak–Higashi syndrome , flavism,  isabellinism ,  xanthochromism ,  axanthism ,  amelanism , and  melanophilin  mutations. Pale patches of skin, feathers, or fur (often referred to as " depigmentation ") can also result from injury. [ 5 ]


Leucism  is often used to describe the  phenotype  that results from defects in  pigment cell  differentiation and/or migration from the  neural crest  to skin, hair, or feathers during  development . This results in either the entire surface (if all pigment cells fail to develop) or patches of body surface (if only a subset are defective) having a lack of cells that can make  pigment .


Since all pigment cell-types differentiate from the same  multipotent  precursor cell-type, leucism can cause the reduction in all types of pigment. This is in contrast to  albinism , for which leucism is often mistaken. Albinism results in the reduction of  melanin  production only, though the  melanocyte  (or  melanophore ) is still present. Thus in species that have other pigment cell-types, for example  xanthophores , albinos are not entirely white, but instead display a pale yellow color.