Albinism

Anatomy or system affected: Eyes, hair, skin

Definition:Condition in which people lack the normal amount of melanin pigment in hair, skin, and/or eyes

Causes and Symptoms

Albinism is a group of rare inherited conditions caused by alteration, or mutation, of one of the genes that affect normal pigment production. Mutation in any one of several genes involved in melanin production can produce individuals with less than the normal amounts of melanin. Lack of melanin can lead to many problems. When melanin is absent from the skin, the skin has no protection against ultraviolet (UV) light and burns easily in the sun. The skin cancer risk for those with albinism is quite high. Lack of melanin in the retina leads to lessened visual acuity. Albinism is classified into two main types, oculocutaneous albinism (OCA) and ocular albinism (OA). The former affects the skin, hair, and eyes, while the latter affects only the eyes.

One form of OCA is called tyrosinase-related OCA. It is an autosomal recessive characteristic; thus, affected individuals must inherit a mutated gene from both of their parents. The parents may themselves have albinism or, more usually, may be normal-appearing heterozygous carriers of this mutation. The enzyme coded by the normal gene, tyrosinase, converts tyrosine to dopa, the first step in the production of melanin. Most commonly, individuals with two copies of the mutated gene lack this enzyme and are unable to produce any melanin. These individuals exhibit classic traits of albinism, which may include pale, unpigmented skin and hair, pale blue/gray or even reddish irises, and severely decreased visual acuity. Less commonly, the mutation in the gene leads to lowered amounts of the enzyme so that the affected person produces some melanin. The amount of melanin produced determines how severely affected the individual will be. These individuals have very little pigment at birth but accumulate more as they age.

Other autosomal recessive OCAs are caused by mutations in the P gene, TRP1 gene, Hermansky-Pudlak syndrome gene, and Chediak-Higashi syndrome gene. In all the above, some pigment is present at birth, but individuals appear less pigmented when compared to siblings.

OA is an X-linked recessive disorder; therefore, it is more often seen in males. Skin, hair, and even iris color are in the normal range for the family, but examination shows a complete lack of pigment in the retina. Visual acuity is less than normal. Female heterozygous carriers show mosaicism, with some parts of the retina pigmented and other parts not.

The various forms of albinism often coincide with symptoms other than the characteristic lack of pigment. A person with albinism may display traits such as nystagmus, or rapid eye movement; strabismus, or crossed eyes; photophobia, or sensitivity to light; and other issues with vision, including functional blindness. Sometimes people with albinism may feel ostracized or alienated due to their appearance or the treatment of others; cultural beliefs and discrimination can exacerbate this problem. An example is the use of the term "albino," which people with albinism find offensive as it categorizes them as an "other" based on their physical appearance.

In the United States, one in every 18,000 to 20,000 people has some form of albinism. In other areas of the world, the ratio is lower at one in every 3,000.

Treatment and Therapy

Although no cure exists for albinism, some of the associated medical issues can be alleviated. Sunscreens of at least SPF 20 offer some protection from harmful UV radiation. Even with sunscreens, however, those with albinism should refrain from sun exposure between 10 AM and 3 PM and wear protective clothing such as hats and long sleeves to block direct sunlight. People with albinism should see a doctor regularly for skin examinations to identify and treat any potential occurrence of skin cancer.

Eye tests should also be undertaken routinely. Various types of eyeglasses, contact lenses, or handheld vision aids can improve vision, although visual acuity is rarely corrected completely. Sunglasses or transitioning lenses that block UV radiation can help protect the eyes from damage. In some cases, surgery may be recommended to treat severe nystagmus or the appearance of strabismus. Most people with albinism have a normal expected lifespan and have normal mental development. Those with Hermansky-Pudlak syndrome or Chediak-Higashi syndrome will typically require more specific, specialized healthcare routines to avoid associated complications.

Bibliography

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