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Albinism

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Albinism is a genetic condition which results in a lack of pigmentation in the eyes, skin and hair. It is an inherited condition caused by altered genes being passed on from an individual's parents. Various problems with vision and eyesight[?] can result from the condition. This entry is intended only to cover human albinism, although many of the features mentioned would probably also apply to albinism in animals.

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Lack of Pigmentation

The altered gene which results in albinism prevents the body making the usual amounts of a pigment called melanin. 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 results in problems with vision, as the eye will not develop properly without the pigment.

Individuals with albinism (called albinos) often have white hair and pale skin which makes them stand out from their families and friends, and from other members of their ethnic group. This can lead to social problems. Growth and development of children with albinism should be normal, however, as should their general health, life span, intelligence, and ability to have children.

Classification

There are two main types of albinism: oculocutaneous[?] albinism (OCA), where melanin pigment is missing in the skin, hair and eyes, and ocular[?] albinism (OA), where the melanin pigment is mainly missing from the eyes, and the skin and hair appear normal. OCA is more common than OA.

Visual Problems Associated with Albinism

People with albinism do not have normal vision. They may have varying degrees of partial-sightedness[?]; either near-sighted[?] or far-sighted[?]. Individuals with these conditions may be helped by the use of glasses, but their vision cannot be corrected completely. Another common condition is nystagmus[?], an involuntary movement of the eyes back and forth. Using a head tilt or turn may reduce the movement and improve vision.

People with albinism are often sensitive to light, a condition called photo-sensitivity[?]. This is due to the iris allowing stray light to enter the eye. This sensitivity may lead to a dislike of bright lights, but does not prevent people with albinism enjoying the outdoors. As mentioned above, they should avoid prolonged exposure to bright sunlight, as their skin is particularly susceptible to sunburn.

Genetics

Albinism is a genetic condition which is inherited from an individual's parents. For OCA, an individual must inherit an altered 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. Where two carriers have a child together, that child will have a one in four chance of getting 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.

To summarise, the lack of pigmentation which arises from the genetic inheritance of people with albinism can result in various visual problems, but need not prevent individuals leading a healthy, full and active life.

Animals

Albinism isn't just restricted to the human species - many other mammals also carry these genes. Albinism tends to be a little more hazardous to survival in the animal kingdom, where vision and pigmentation are usually strongly linked to survival. Bristol Zoo is the home to a very rare albino penguin named Snowdrop.



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