Albinism

Albinism is a genetic condition resulting in a lack of pigmentation in the eyes, skin and hair. It is an inherited condition arising from the combination of recessive genes passed from both parents of an individual. A variety of problems with photosensitivity in eyesight and skin usually result from the condition. This article is intended to cover mainly human albinism, although many of the features mentioned would probably also apply to albinism in other animals.

Lack of pigmentation

The gene which results in albinism prevents the body from making the usual amounts of a pigment called melanin. Albinism is typically categorised as Tyrosinase positive or negitive. In cases of Tyrosinase positive albinism, the enzyme tyrosinase is present but is unable to enter pigment cells to produce melanin. In tyrosinase negative cases, this enzyme is not produced.

There are many genes which are now scientifically proven to be associated with albinism (or better: alterations of the genes). All alterations, however, lead to an alteration of the melanin (pigment/coloring) production in the body. Melanin helps protect the skin from ultraviolet light coming from the sun (see human skin color for more information). People with albinism lack this protective pigment in their skin, and can burn easily from exposure to the sun as a result. Lack of melanin in the eye often results in problems with vision, as the eye will not develop properly without the pigment.

Individuals with full albinism (called albinos) generally have flax-white hair, blue eyes and pale white skin which makes them stand out. Sometimes hair pigmentation is not completely absent (white) but shows a pale or medium blonde. Often the affected persons are paler in complexion than the rest of the family. The myth that all persons with albinism have "white hair and red eyes" is not true. Colorless iris in humans is pale blue, not pink like in some animals, and the human eye is too deep for the pupil to appear red rather than black.

Growth and development of children with albinism should be (and is) normal however, as should their general health, life span, intelligence, and ability to have children. The chance of albino children resulting from the marriage of an albino with a non-albino is very low and is discussed below.

Visual problems associated with albinism

People with albinism generally suffer impaired vision. They may have varying degrees of partial-sightedness; either near-sighted or far-sighted. Most albinos suffer nystagmus (a rapid, involuntary "shaking" of the eyes) or stigmatism, though this and general vision often improves towards middle age, when most "normally" sighted individuals begin to suffer long- or short-sightedness, due to changes in muscle tension.

Individuals with these conditions may be helped by the use of glasses and low-visual aids such as magnifiers, as well as bright but angled reading lights, but their vision cannot be corrected completely. Although surgery is possible on the ocular muscles, effectively simulating (to a limited degree) the improvements in the albino's vision that often come with age, the gain is generally thought be out-weighed by the trauma.

The lack of pigment in the eye generally leads to ocular photophobia or hyper-photo-sensitivity. This is due not so much by the iris allowing stray light to enter the eye, as by a lack of pigment within the eye, allowing light to refract within the eyeball. A good analogy would be taking a picture with a film camera that is painted white within, rather than black. Such sensitivity generally leads to a dislike of bright lights, but does not prevent people with albinism enjoying the outdoors. They should avoid prolonged exposure to bright sunlight regardless, as their skin is particularly susceptible to sunburn.

Genetics

In ocular-cutaneous albinism, individuals inherit an "albinism gene" from both parents. Where an individual receives one albinism gene and one normal gene, that person will not show outward signs of the condition, but will become a carrier of the recessive gene. Where two carriers of the recessive gene have a child together, that child will have a one in four chance of receiving two albinism genes, and having albinism. The child will have one in four chances of getting neither albinism gene, having normal pigment, and not being a carrier. The child has two in four chances of getting one normal and one albinism gene, having normal pigment but being a carrier. The incidence of carriers in the British population is approximately 1 in 50.

Culture

In Jamaica, albinos have long been denigrated and regarded as cursed. In recent times, the albino dancehall singer Yellowman has helped to end this perception.

Several movies have featured evil pale-skinned characters.

See also: List of albinos

Albinism in non-humans

Albinism is not restricted to the human species—other animals also carry these genes. Albinism tends to be more hazardous in the animal kingdom, where vision and pigmentation are usually strongly linked to survival. However, albino animals are often kept as pets, e.g. albino gerbils.

There have been no reports of true albinism in horses. White horses lack the pink eyes that make a true albino.

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.

Cats can carry genetic albinism, resulting in white fur and blue eyes. A high percentage of albino cats are also deaf.

Albino frogs and fish are found in the wild, and can sometimes be found for sale in pet shops. The lack of pigment is seen as a desired attribute for breeders and keepers of these animals.

See also

• Vitiligo (or leukoderma), the patchy loss of skin pigmentation

External links

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• The UK Albinism Fellowship (http://www.albinism.org.uk)
• NOAH The National Organization for Albinism and Hypopigmentation US (http://www.albinism.org)
• Albinismus (German Language) (http://www.albinismus.info)
• Biblical references (http://sd.gospelcom.net/072.html) - William Blake's Ancient of Days was based upon the Revelation of St John the Divine, 1:14: *:"His head and hair were white like wool, as white as snow, and His eyes like a flame of fire*
• Albino frogs (http://allaboutfrogs.org/weird/strange/albino.html)
• Albino Tiger Barb (http://freshaquarium.about.com/cs/cyprinids2/p/albinotigerbarb.htm)
• Albino Corydorus paleatus (http://animal-world.com/encyclo/fresh/catfish/acory.php)
• Pale Riders Who Wear Black Hats (http://www.wired.com/news/culture/0,1284,58599,00.html) - Wired News article on albinism in cinemada:Albinisme

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