Albinism

Definition

Albinism is a defect of melanin production. This defect results in the partial or full absence of pigment (color) from the skin, hair, and eyes.

Alternative Names

Causes

Albinism results when the body is unable to produce or distribute pigment, called melanin, because of one of several possible genetic defects. In Type 1 albinism, defects in the metabolism of tyrosine lead to failure in converting this amino acid to melanin. This is due to a genetic defect in tyrosinase -- the enzyme responsible for metabolizing tyrosine.

Type 2 albinism is due to a defect in the "P" gene. Those with this type have slight pigmentation at birth.

In the most severe form of albinism (called oculocutaneous albinism), those affected appear to have hair, skin, and iris color that are white or pink as well as vision defects. This is inherited via an autosomal recessive process.

Albinism of just the eyes also occurs. This is called ocular albinism type 1 (OA1) and can be inherited via either an X-linked or an autosomal recessive process. In this form of albinism, skin color is usually normal and eye color may be in the normal range. However, examination of the eye will show that there is no pigment in the retina.

Hermansky-Pudlak syndrome (HPS) is a single-gene disorder inherited in an autorecessive manner. It is a form of albinism associated with a bleeding disorder as well as lung and bowel diseases. If a person with albinism has unusual bruising or bleeding, this syndrome should be considered.

Other complex diseases may be associated with localized albinism (loss of pigment in only a specific area). These include:

• Waardenberg syndrome (often a white forelock -- a lock of hair that grows on the forehead, or absence of pigment in one or both irises)
• Chediak-Higashi syndrome (allover, but not complete, lack of pigment in the skin)
• Tuberous sclerosis (white leaf macule) -- small localized areas of depigmentation)

Symptoms

For those with albinism, one of the following will be present:

• Absence of pigment from the hair, skin, or iris of eyes
• Patchy absence of pigment (skin color, patchy)
• Lighter than normal skin and hair

Many forms of albinism have some of the following possible symptoms:

• Rapid eye movements (nystagmus)
• Strabismus (eyes not tracking properly)
• Photophobia (avoidance of light because of discomfort)
• Decreased visual acuity or even functional blindness

Exams and Tests

The most accurate way to determine albinism and the specific type is genetic testing. This is helpful  in families with albinism and is useful for specific, isolated populations such as the Hopi Indian tribe of the Southwestern U.S.

There are several ethnic groups in Central and South American who carry this trait. A small blood sample is obtained from the affected individual and the parents and molecular genetic analysis of the DNA code is performed to identify the affected genes.

The disorder may also be diagnosed based on the appearance of the skin, hair, and eyes. It is very helpful for an ophthalmologist to perform a complete examination of anyone with albinism. A electroretinogram test, to determine brain waves produced by light shined in the eye, can reveal "abnormal wiring" of the visual system in ocular forms of albinism.

Treatment

Treatment aims to ease symptoms and depends on the extent of the disorder.

The skin and eyes must be protected from the sun. Sunglasses (UV protected) may relieve photophobia. Sunburn risk can be reduced by avoiding the sun, by using sunscreens and covering completely with clothing when exposed to sun. Sunscreens should have a high SPF (sun protection factor).

Support Groups

National Organization for Albinism and Hypopigmentation

www.albinism.org

International Albinism Center

albinism.med.umn.edu

Hermansky-Pudlak Syndrome Network

www.hpsnetwork.org

Outlook (Prognosis)

Mostly, albinism does not change one's expected lifespan. For those with Hermansky-Pudlak syndrome, however, life expectancy may be shortened due to lung disease or bleeding problems.

Activities for those with albinism may be limited by intolerance to the sun.

Possible Complications

• Skin cancer
• Decreased vision, blindness

When to Contact a Medical Professional

Call your health care provider if you have albinism or symptoms such as photophobia that cause discomfort. Also call if there are any skin changes that might be an early sign of skin cancer.

Prevention

As this is a large group of inherited conditions genetic counseling is important. Genetic counseling should be considered for individuals with a family history of albinism or hypopigmentation.