Albinism

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Albinism
Classifications and external resources
Albinistic Taiwanese young woman, 2005
ICD-10 E70.3
ICD-9 270.2
OMIM {{{OMIM}}} 203100 203200 203290 203280 278400 606574 203300 214500 214450 607624 609227 604228 256710 300500 300600 300650 103470 203310 300700 220900 600501
DiseasesDB 318
MedlinePlus 001479
eMedicine derm/12 

Albinism (from Latin albus, meaning "white"), more technically hypomelanism or hypomelanosis, is a form of congenital hypopigmentary disorder, characterized by a lack of pigment in the eyes, skin and hair (or more rarely the eyes alone). Albinism results from inheritance of recessive genes. The condition is known to affect mammals, fish, birds, reptiles, and amphibians. While the most common term for an organism affected by albinism is "albino" (noun and adjective), the word is sometimes used in a derogatory way towards people; more neutral terms are "albinistic" (adjective) and "person with albinism" (noun). Another more clinical adjective sometimes used to refer to animals is "albinoid".

Contents

Causes

Albinism is a genetic disorder; it is not an infectious disease and cannot be transmitted through contact, blood transfusions, etc. The principal gene which results in albinism prevents the body from making the usual amounts of the pigment melanin. Most forms of albinism are the result of the biological inheritance of genetically recessive alleles (genes) passed from both parents of an individual, though 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.[1][2]

Albinism used to be categorized as tyrosinase-positive or -negative. In cases of tyrosinase-positive albinism, the enzyme tyrosinase is present. The melanocytes (pigment cells) are unable to produce melanin for any one of a variety of reasons that do not directly involve the tyrosinase enzyme. In tyrosinase negative cases, either the tyrosinase enzyme is not produced or a nonfunctional version is produced. (This classification has been rendered obsolete by recent research.[citation needed])

The chance of offspring with albinism resulting from the pairing of an organism with albinism and one without albinism is low, as discussed in more detail below. However, because organisms can be carriers of genes for albinism without exhibiting any traits, albinistic offspring can be produced by two non-albinistic parents. Albinism affects males and females equally, showing no gender skew.[1]

Because organisms with albinism have skin that lacks (sufficiently or entirely) the dark pigment melanin, which helps protect the skin from ultraviolet radiation coming from the sun, they can sunburn easily from overexposure. (See human skin color for more information). Lack of melanin in the eye also results in problems with vision, related and unrelated to photosensitivity, which are discussed further below.

Albino peacocks (behind pigmented ones)
Enlarge
Albino peacocks (behind pigmented ones)

Most organisms with albinism appear white or very pale; melanin (or more accurately, melanins — there are multiple types) are responsible for brown, black, gray, and some yellow colorations. In some animals, especially birds and reptiles, ruddy and yellow hues or other colors may be present on the entire body or in patches (as is common among pigeons), due to the presence of other pigments unaffected by albinism such as porphyrins, pteridines and psittacins, and carotenoids derived from the diet. Some animals are white or pale due to chromatophore (pigment cell) defects, do not lack melanin production, and have normal eyes; they are referred to as leucistic. The direct opposite of albinism, an unusually high level of melanin pigmentation (and sometimes absence of other types of pigment in species that have more than one), is known as melanism, and results in an appearance darker than non-melanistic specimens from the same genepool.[3] Albinism-like conditions may affect other pigments or pigment-production mechanisms in some animals (e.g. "whiteface", a lack of psittacins that can affect some parrot species.)[4]. Another is common in reptiles and amphibians: axanthism, in which xanthophore metabolism instead of synthesis of melanin is affected, resuling in reduction or absence of red and yellow pteridine pigments. [5] Of all these conditions, only albinism and melanism affect humans.

The eyes of an animal with albinism occasionally appear red due to the underlying blood vessels showing through where there is not enough pigment to cover them. In humans this is rarely the case, as a human eye is quite large and thus produces enough pigment to lend opacity to the eye. However, there are cases in which the eyes of an albinistic person appear red or purple, depending on the amount of pigment present.

The albinistic are generally (but see related disorders below) as healthy as the rest of their species, with growth and development occurring as normal, and albinism by itself does not cause mortality[1] (though the lack of pigment is an elevated risk for skin cancer, etc.) Many animals with albinism, however, lack their protective camouflage and are unable to conceal themselves from their predators or prey; the survival rate of animals with albinism in the wild is usually quite low. Humans with albinism commonly have vision problems and need sun protection, but also face a social challenge, as the condition is often a source of discrimination against them.

About 1 in 17,000 human beings have some type of albinism, although up to 1 in 75 are carriers of albinism genes. While some of the very rare albinism disorders that are coupled with deafness and immunodeficiency appear to be linked with inbreeding[2], the vast majority of sufferers of common albinism are not the product of such unions; the more usual albinism genes are widespread enough that they can easily produce albinistic offspring from parents that are not related.

Genetic testing can confirm albinism and what variety it is, but offers no medical benefits except in the cases of non-OCA disorders (see below) that cause albinism along with other medical problems (which may be treatable). Albinism itself cannot be treated.

Types of albinism

There are two main categories of albinism in humans. In oculocutaneous albinism, pigment is missing from the hair, eyes, and skin. In ocular albinism, only the eyes lack pigment. People with oculocutaneous albinism can have no pigment at all to almost-normal levels. People who have ocular albinism have normal skin and hair color, and many even have a normal eye appearance. While there is only one major type of ocular albinism, there are several varieties of oculocutaneous albinism (and disorders which produce the same or similar results), some of which have subtypes. Some are easily distinguished by appearance, but in most cases, genetic testing is the only way to be certain.

  • Oculocutaneous albinism type 1 (OCA1) (Mendelian Inheritance in Man (OMIM) 203100) is the type with (usually) the least amount of pigment. People with this type generally have very pale skin, "white" (actually translucent) hair and light blue eyes, however there are cases in which the eyes appear red or purple, depending on the amount of pigment present in the irises and the level of light available to the observer. OCA1 is caused by an alteration of the tyrosinase gene, and can occur in two variations. The first is OCA1a, and means that the organism cannot develop pigment at all. Vision usually ranges from 20/200 to 20/400. The second is OCA1b, which has several subtypes itself. Many individuals with OCA1b can tan and develop pigment[citation needed]. One subtype of OCA1b is called OCA1b TS (temperature sensitive), where the tyrosinase can only function below a certain temperature, which causes the body hair in cooler body regions to develop pigment (i.e. get darker). An equivalent mutation produces the coat pattern in Siamese cats[citation needed]. About 1 in 40,000 people have OCA1.[1][2]
  • Oculocutaneous albinism type 2 (OCA2) (OMIM: 203200), the most common type of albinism, is caused by mutation of the P gene. People with OCA2 generally have more pigment and better vision than those with OCA1, but cannot tan like some with OCA1b. A little pigment can develop in freckles or moles[citation needed]. People with OCA2 usually have fair skin but not as pale as OCA1, and pale blonde to golden or reddish-blonde hair, and most commonly blue eyes. Affected people of African descent usually have a different phenotype (appearance): yellow hair, pale skin, and blue, gray or hazel eyes. About 1 in 15,000 people have OCA2.[1][2]
  • Oculocutaneous albinism type 3 (OCA3, or rufous albinism) (OMIM: 203290) has only been partially researched and documented. It is caused by mutation of the tyrosinase-related protein-1 (Tyrp1) gene. Cases have been reported in Africa and New Guinea. Affected individuals typiocally have red hair and reddish-brown skin and blue or gray eyes. Variants may be the recently-identified minimal pigment type albinism (OMIM: 203280) and rufous oculocutaneous albinism (ROCA or xanthism) (OMIM: 278400). The incidence rate of OCA3 is unknown.[1][2]
  • Oculocutaneous albinism type 4 (OCA4) (OMIM: 606574) is very rare (except in Japan where OCA4 accounts for 24% of albinism cases.) OCA4 can only be distinguished from OCA2 through genetic testing, and is caused by mutation of the membrane-associated transporter protein (MATP) gene.[1][2]
  • Hermansky-Pudlak syndrome (HPS) (OMIM: 203300) is not a type of OCA, technically, but has similar features. HPS has a great range of degrees of pigmentation, from OCA1a-like to almost-normal coloring. Vision usually ranges from 20/60 to 20/200. Apart from the hypopigmentation and impaired vision, people with HPS lack dense bodies in their blood platelets which are responsible for releasing clotting factors. For this reason, HPS patients bruise easily and have a hard time stopping bleeding once it begins (hemophilia, also known as bleeding diathesis). HPS has seven known forms (HPS-1 through HPS-7), each caused by a different autosomal recessive gene mutation. HPS-1 and HPS-4 may also include pulmonary fibrosis, or scarring of lung tissue that prevents the necessary expansion and contraction during breathing. It is believed that this is due to a buildup of fatty ceroid in the lungs. Colitis, or inflammation in the large intestine, is another symptom of most types of HPS, which may cause diarrhea, nausea, and blood in the stool. HPS is rare generally, but affects 1 in 1800 Puerto Ricans, and is typically fatal by middle age.[1][2]
  • Chediak-Higashi syndrome (CHS) (OMIM: 214500), like HPS, is not technically a form of OCA, but produces similar results. CHS, caused by mutation of the LYST gene, is very rare, and is associated with other medical problems, such as immune system dysfunction that leads to a high infant mortality rate, HPS-like hemophilia, and neurological problems, among many others, in 85% of sufferers.[1][2]
  • Griscelli syndrome (GS) is similar to CHS in symptoms (and also very rare). It is divided into three types, GS1 (OMIM: 214450), GS2 (OMIM: 607624) and GS3 (OMIM: 609227). Each type is due to a different autosomal recessive gene mutation. Type 1 produces mainly neurological problems in addition to albinism, while type 2 produces mainly immunological issues as well as the hypopigmentation, and type 3 only evidences hypomelanosis without either of the other sorts of problems. Sufferers of GS differ in appearance from those with OCA, having silvery-grey hair. A fourth and even rarer variant, partial albinism and immunodeficiency syndrome (PAID) (OMIM: 604228), has been identified and requires further study. An additional type called Elejalde syndrome (OMIM: 256710) may exist, but some researchers believe it is actually simply GS1. GS2, because of its immune system effects, results in a very high mortality rate among children and young adults that have it.[1][2]
  • Ocular albinism only affects the eyes. Ocular albinism, type 1 (OA1) (OMIM: 300500) is the most common variety There are several other identified types, though researchers are not all agreed on the distinctions and classification. Most are caused by a mutation in a gene on the X chromosome, and are X-linked recessive traits. Ocular albinism, type 2 (OA2) (OMIM: 300600). Another is known as ocular albinism with sensorineural deafness (OASD) (OMIM: 300650), and as its name implies is associated with loss of hearing. A rare non-X-linked recessive gene variant is known as Waardenburg syndrome, type 2, with ocular albinism (WS2-OA) (OMIM: 103470). Yet another non-X-linked variant is ocular albinism, autosomal recessive (OAR) (OMIM: 203310). Skin color of sufferers of OA can be slightly lighter than those of the rest of the family. The eye color can vary greatly, and in some cases only examination of the retina or genetic testing can reveal OA for certain. OA afflicts 1 in 50,000 people.[1][2]
  • Other rare variants are theorized (by ongoing research as of 2006) to exist, such as albinism-deafness syndrome (ADFN) (OMIM: 300700, which may actually be closer related to vitiligo); recessive total albinism with congenital deafness (OMIM: 220900); and albinism black-lock cell-migration disorder syndrome (ABCD) (OMIM: 600501)[2]

Visual and other health problems

Eye conditions common in albinism may include (but will not necessarily be present for all):

Organisms with albinism suffer from impaired vision, but the degree varies greatly. While a person with albinism may suffer from a standard eye affliction like near-sightedness or far-sightedness, the biggest problem arises from a poorly-developed retina (foveal hypoplasia) and abnormal nerve connections between the eyes and brain. These abnormalities define albinism, medically. While the effects of this condition are difficult to describe, it can be explained as seeing at a lower resolution. Additionally, most people with albinism suffer from nystagmus (a rapid, involuntary "shaking" of the eyes) which further reduces vision. People with albinism are also likely to have astigmatism or strabismus.

The iris, the normally dark area in the center of the eye, does not have enough pigment to screen out stray light coming into the eye. Light normally enters the eye only through the pupil, the dark opening in the center of the iris, but in albinism light can pass through the iris as well. Such sensitivity (photophobia) generally leads to a dislike of bright lights, but does not prevent people with albinism enjoying the outdoors, especially when using sunglasses and/or brimmed hats. They should avoid prolonged exposure to bright sunlight regardless, as their skin is particularly susceptible to sunburn (see below).

Sun protection and vision aids

Albinism is a condition that cannot be "cured" or "treated" per se, but small things can be done to improve the quality of life for those affected. It is vital that people with albinism use sunscreen when exposed to sunlight to prevent premature skin aging or skin cancer. This poses a problem for those who cannot afford sunscreen, especially in countries with high exposure to sunlight, as in Africa. Special sun protective clothing and swimsuits are available and are a good alternative to excessive use of sunscreen.

For the most part, treatment of the eye conditions consists of visual rehabilitation. Surgery to correct strabismus may improve the appearance of the eyes. However, since surgery will not correct the misrouting of nerves from the eyes to the brain, surgery will not provide fine binocular vision. In the case of esotropia or "crossed eyes," surgery may help vision by expanding the visual field (the area that the eyes can see while looking at one point). Nystagmus damping surgery can also be performed, to reduce the "shaking" of the eyes back and forth.

Glasses and other vision aids such as magnifiers, large-print materials or closed captioning, as well as bright but angled reading lights can help individuals with albinism, even though their vision cannot be corrected completely. Some people do well using bifocals which have a strong reading lens, prescription reading glasses, hand-held magnifiers or special small telescopes. Contact lenses, may be colored to block light transmission through the aniridic iris. 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 U.S. states allow the use of bioptic telescopes for driving. (See also NOAH bulletin "Low Vision Aids".)

Although still disputed among the experts, many ophthalmologists recommend the use of glasses from early childhood on to allow the eyes the best development possible. Surgery is possible on the ocular muscles to decrease nystagmus, strabismus and common refractive errors, but especially with nystagmus surgery the effectiveness varies greatly and depends on individual circumstances.

Optometrists or ophthalmologists who are experienced in working with low vision patients can recommend various optical aids. Clinics should provide aids on trial loan, and provide instruction in their use. The American Foundation for the Blind (1-800-AFB-LIND) maintains a directory of low vision clinics.

Use of sunglasses and hats with wide brims can make the glare outside bearable. Other things that can help people with albinism are avoiding sudden changes of the lighting situation (switching the light on in complete darkness), using dimmable switches and adding tint to car windows or blinds to normal windows. Lights should be yellowish rather than blue and not point towards the usual position of a person with albinism (like their seat at a table). When possible, people with albinism generally prefer to have the light on their backs rather than face it.

Culture

Under the Spanish casta, albino (or albina, if female) was the term used to categorize an individual who was one-eighth African and seven-eighths Spanish.

Myths and superstitions

Due to albinism's effect on one's outward appearance, cultures around the world have developed many myths and superstitions regarding people with albinism:

  • A common misconception is that albinistic individuals of a species are sterile; they are in fact fully capable of reproducing.
  • Folklore has developed in Zimbabwe that having sex with a woman with albinism will cure a man of HIV. This has led to many women with albinism in the area being raped [6] (and thus infected) by HIV-positive men.
  • In Jamaica, people with albinism were historically degraded and regarded as "cursed". In recent times, the albinistic musicians "King Yellowman" and "Prince Yellowman" (see below) have helped to curb this stereotype.
  • In some cultures, people with albinism are thought to have magical powers or to be able to tell the future[citation needed].
  • It is also thought by many that people with albinism live short life spans. This is not true, but may be a distorted view of a more reasonable fact that people with albinism have a higher risk of skin cancer if they do not use proper skin protection when in the sun [citation needed].

Other

Snowdrop, an albino African Penguin, born at Bristol Zoo (England), died in August 2004. Snowdrop would normally have looked like the background penguins
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Snowdrop, an albino African Penguin, born at Bristol Zoo (England), died in August 2004. Snowdrop would normally have looked like the background penguins

Bristol Zoo was the home to a very rare albino African penguin named Snowdrop. Snowdrop was hatched at the zoo in October 2002 and died in August 2004. For many years, a unique albino gorilla named Floquet de Neu (Snowflake) was the most famous resident of the Parc Zoològic de Barcelona. An albino humpback whale travels up and down the east coast of Australia, and has become famous in the local media. The whale is called Migaloo (the Aboriginal word for "white lad").

Medical science and toxicology can take advantage of the standardized lack of pigment in albino animals in testing for materials' chemical properties. An example of such a test is the test for corrosiveness, which is a skin exposure test performed on albino rabbits.

The 2004 book Weird U.S. chronicled (and further popularized) one of the lesser known local legends of the country, "albino colonies". The book uses firsthand accounts mailed to the authors to paint a picture of various locations in the U.S. (most notably Clifton, New Jersey) where aggregations of albino families live in seclusion. The accounts tell tales of honking horns to try to bring the residents out of their houses, of gawkers being shot at with rock salt by residents, and even gangs of local albinistic vigilantes.

Famous people with albinism

In popular culture

Portrayals of persons with albinism in literature and film are rarely positive. This fact is referred to as albino bias or the "evil albino" stereotype. Positive or at least neutral depictions are listed concisely below; see the albino bias article for a list of negative portrayals, for a general discussion of the trend and its exceptions, and for more detail on such characters, both positive and negative.

  • "Powder", the titular character in the movie Powder (a characterization which can be criticized because his condition is implied to give him supernatural abilities, and because the name can be seen as mocking or derogatory; however the depiction can been seen as positive, in its portrayal of the effects of bias against those with albinism).
  • "Whitey", in the movie Me, Myself and Irene (His nickname and his treatment in the film can be seen as derogatory, but on the other hand are accurately representative of the casual discrimination that persons with albinism are often made to suffer; further, the character is accurately shown as having impaired vision).
  • Elric of Melniboné, the OCA protagonist of an eponymous series of fantasy novels by Michael Moorcock, is both hero and anti-hero. (Moorcock's apparently imperfectly-informed description of this character's condition is somewhat exaggerated, and coupled with a general frailty that the character must overcome with sorcery and medicines, but the character's weaknesses are narratively incidental, being used to contrast with the stereotype of the muscle-bound barbarian common in fantasy novels. Overall, the characterization is sympathetic.)
  • Elrod the Albino, a parody of Elric (above), in the comic book series Cerebus by Dave Sim.
  • Taarna, heroine of the final segment of the animated film Heavy Metal (not necessarily a person with natural, genetic albinism, though the distinction would be lost on most viewers).
  • Bran Davis, in "The Dark Is Rising" occult novel series (a positive portrayal, but somewhat inaccurate because the character lacks any vision problems.)
  • Silas, in the book The Da Vinci Code by Dan Brown, is described as being albinistic. He is a religious fanatic and an assassin who murders several people, though he is portrayed somewhat sympathetically as having mental problems and having been effectively brainwashed.
  • Bjørn Beltø, in Tom Egeland's Norwegian novel Sirkelens Ende (pre-dating but very similar to The Da Vinci Code, coincidentally it features an albinistic person in a positive light while the latter does the opposite.)
  • "U.V.", in the film Disturbing Behavior, (a neutral portrayal; he is not a villain, but has a mocking nickname)
  • "Snow", an albinistic psychic who achieves a messianic following, has his story told in Snow, a concept album by progressive rock band; Spock's Beard
  • Pete White in The Venture Bros. animated series on "Adult Swim". An albinistic computer scientist and friend of Dr. Venture from his college years, he runs "Conjectural Technologies" with Master Billy Quizboy, Boy Genius. (Note that the name is stereotypical, but his intelligence is accentuated.)
  • The art teacher in the "Riley Wuz Here" episode of the "Adult Swim" cartoon The Boondocks, though never explicitly described as such in dialogue nor in narration, is quite possibly an African-American with albinism. (Though described by the character of Riley as being "a white guy", he possesses typically African facial features, a large and smooth blonde afro hairstyle, and red irises in his eyes (despite the fact that truly red eyes in humans with albinism is a rarity. While it is interesting to note that no characters really seem to notice the character's apparent (if inaccurate) albinism, there are implications on the show that the character is crazy. On the other hand, the character may simply be a parody of Bob Ross.)
  • Harold Kline, in Ghost Boy, a novel by Iain Lawrence, is an albinistic youth who ran away from home and ended up working in the circus with the other "freaks", as people called them.
  • Arthur "Boo" Radley, in To Kill a Mockingbird, is physically described in a way that suggests albinism. (He is also described as reclusive and is an object of fear and superstition, but his actions are generally altruistic.)
  • Ceecee, a fictional character in "The Mediator", a novel series by Meg Cabot (a.k.a. Jenny Caroll). Ceecee is portrayed fairly accurately as a person with albinism. She wears protective clothing, sunscreen, hats, and sunglasses whenever she goes outside. However, she is described as having purple irises even though that is rare. Ceecee is also described as intelligent, and is rather accurately described as receiving some ridicule from her classmates. On the other hand, Ceecee's aunt, who also has albinism, reads tarot cards and speaks with the dead.
  • Dilandau Albatou and Folken Fanel, characters in the fantasy anime series Escaflowne. Both appear to intended to represent persons with albinism, with fair skin, red irises and pale hair. Their moral portrayal is ambiguous; both cause great destruction but in the end are revealed to have been a victim of circumstances, and misguidedly well-meaning, respectively.
  • Rei Ayanami, in Neon Genesis Evangelion may be perceived as albinistic (this is not explicited stated in the story).
  • Misaki Saiki, an albino dominatrix, is the principle heroine in Ghost Talker's Daydream.
  • "An albino" (along with "a mulato") features prominently in the chorus of Nirvana's hit song about teenage angst and high school factionalism, "Smells Like Teen Spirit".

See also

  • Vitiligo (or leukoderma), the patchy loss of skin pigmentation
  • Melanism (or melanosis), the condition of having an unusually high level of skin pigmentation
  • Hermansky-Pudlak syndrome, a condition similar to albinism
  • Leucism, a similar condition in animals, characterized by reduced pigmentation
  • Albino bias in fiction

References

  1. ^ a b c d e f g h i j k "Albinism"], by Dr. Raymond E. Boissy, Dr. James J. Nordlund, et al., at eMedicine
  2. ^ a b c d e f g h i j k Online Mendelian Inheritance in Man Database, at Johns Hopkins University (see also Mendelian Inheritance in Man for more information about this source).
  3. ^ "Feather Colors: What We See" by Dr. Julie Feinstein of the American Museum of Natural History (NY), in Birder's World Magazine" online archive; sourced December 2006, actual authoring/publication date unspecified.
  4. ^ "The Parblue Puzzle: Part 4 — Common Parblue Varieties: The Cockatiel [Nymphicus hollandicus]" by Clive Hesford, The Genetics of Colour in the Budgerigar and Other Parrots, January 1998
  5. ^ "Amphibian Biology & Physiology: Caudata" at Amphibian Information Resource: An Educational Web Project About Amphibian Species; sourced December 2006, actual authoring/publication date unspecified.
  6. ^ ipsnews.net

External links

Albinism in humans

Albinism support organizations

  • Positive Exposure - Non-profit organization founded by fashion photographer Rick Guidotti, "dedicated to celebrating the spirit of difference". Focuses on genetic conditions, especially albinism.
  • Albinism International - Online support community for people with albinism and their family members
  • NOAH - The National Organization for Albinism and Hypopigmentation (USA)
  • The UK Albinism Fellowship
  • ALBA - Spanish association for albinism (Spanish)
  • OLA - Latinamerican Albinism Association. (Spanish)

Other

Albinism in animals

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