Albinism, Oculocutaneous, Type I
Patient Information
Characteristics
Background and History
The condition known as albinism has been known since antiquity. In fact, the biblical Noah is claimed by some to have been an albino. Multiple types have been described and all are caused by mutations in genes that are involved in the synthesis of pigment.
Clinical Correlations
This type of albinism is characterized by lack of pigmentation in the eyes, hair and skin. There are secondary changes in the retinas (light sensing tissue inside the eye) of the eye that lead to dysfunction of the rods and cones resulting in loss of vision. The condition is present at birth as white skin and hair. The colored part of the eye (iris) is generally pale blue. The normal color of the inside of the eye is not present and appears ‘blond’. The eyes usually have a to-and-fro motion (nystagmus) and are unable to fixate on a target. Vision is stable in the range of 20/50 to 20/200. Sensitivity to light (photophobia) can be marked. Some patients have a hearing deficit as well.
People with a subtype of this condition may have darkening of the skin, hair, and iris as they grow older but the vision does not improve.
Genetics
Inheritance
Oculocutaneous albinism is inherited in an autosomal recessive pattern. Two mutations are required before the disease is expressed and these are contributed by the normally pigmented parents. Such parents can expect on average that 1 in 4 of their children will have this condition.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
The diagnosis is generally made by pediatricians and ophthalmologists at birth. There is no treatment for the lack of pigmentation or the decreased vision. Precautions should be taken to protect the skin from sunburn and dark glasses are helpful in reducing the discomfort from light. Patients can expect to live a normal lifespan but their visual function can be improved by low vision aids.
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