Oculocutaneous albinism

Oculocutaneous albinism is a group of conditions that affect coloring (pigmentation) of the skin, hair, and eyes. Affected individuals typically have very fair skin and white or light-colored hair. Long-term sun exposure greatly increases the risk of skin damage and skin cancers, including an aggressive form of skin cancer called melanoma, in people with this condition. Oculocutaneous albinism also reduces pigmentation of the colored part of the eye (the iris) and the light-sensitive tissue at the back of the eye (the retina). People with this condition usually have vision problems such as reduced sharpness; rapid, involuntary eye movements (nystagmus); and increased sensitivity to light (photophobia).

The four types of oculocutaneous albinism are designated as type 1 (OCA1) through type 4 (OCA4). Oculocutaneous albinism type 1 is characterized by white hair, very pale skin, and light-colored irises. Type 2 is typically less severe than type 1; the skin is usually a creamy white color and hair may be light yellow, blond, or light brown. Type 3 includes a form of albinism called rufous oculocutaneous albinism, which usually affects dark-skinned people. Affected individuals have reddish-brown skin, ginger or red hair, and hazel or brown irises. Type 3 is often associated with milder vision abnormalities than the other forms of oculocutaneous albinism. Type 4 has signs and symptoms similar to those seen with type 2. Because their features overlap, the four types of oculocutaneous albinism are most accurately distinguished by their genetic cause.

How common is oculocutaneous albinism?

Overall, an estimated 1 in 20,000 people worldwide are born with oculocutaneous albinism. The condition affects people in many ethnic groups and geographical regions. Types 1 and 2 are the most common forms of this condition; types 3 and 4 are less common. Type 2 occurs more frequently in African Americans, some Native American groups, and people from sub-Saharan Africa. Type 3, specifically rufous oculocutaneous albinism, has been described primarily in people from southern Africa. Studies suggest that type 4 occurs more frequently in the Japanese and Korean populations than in people from other parts of the world.

What genes are related to oculocutaneous albinism?

Mutations in the OCA2, SLC45A2, TYR, and TYRP1 genes cause oculocutaneous albinism.

Mutations in the MC1R gene modify the course of oculocutaneous albinism.

The four types of oculocutaneous albinism each result from mutations in a single gene: TYR, OCA2, TYRP1, or SLC45A2. Changes in the TYR gene cause type 1; mutations in the OCA2 gene are responsible for type 2; TYRP1 mutations cause type 3; and changes in the SLC45A2 gene result in type 4. These genes are involved in producing a pigment called melanin, which is the substance that gives skin, hair, and eyes their color. In the retina, melanin also plays a role in normal vision. Mutations in any of these genes disrupt the ability of cells to make melanin, which reduces pigmentation in the skin, hair, and eyes. A lack of melanin in the retina leads to the vision problems characteristic of oculocutaneous albinism.

Alterations in the MC1R gene can change the appearance of people with oculocutaneous albinism type 2. This gene helps regulate melanin production and is responsible for some normal variation in pigmentation. People with genetic changes in both the OCA2 and MC1R genes have many of the usual features of oculocutaneous albinism type 2, including light-colored eyes and vision problems; however, they typically have red hair instead of the usual yellow, blond, or light brown hair seen with this condition.

Read more about the MC1R, OCA2, SLC45A2, TYR, and TYRP1 genes.

How do people inherit oculocutaneous albinism?

Each of the four types of oculocutaneous albinism is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but do not show signs and symptoms of the condition.

What other names do people use for oculocutaneous albinism?

• Albinism, Oculocutaneous
• OCA

Where can I find information about treatment for oculocutaneous albinism?

These resources address the management of oculocutaneous albinism and may include treatment providers.

• Gene Review: Oculocutaneous Albinism Type 1
• Gene Review: Oculocutaneous Albinism Type 2
• Gene Review: Oculocutaneous Albinism Type 4
• MedlinePlus Encyclopedia: Albinism

You might also find information on treatment of oculocutaneous albinism in Educational resources and Patient support.

Where can I find additional information about oculocutaneous albinism?

You may find the following resources about oculocutaneous albinism helpful. These materials are written for the general public.

• MedlinePlus - Health information (3 links)
• Educational resources - Information pages (7 links)
• Patient support - For patients and families (6 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

• Gene Reviews - Clinical summary (3 links)
• Gene Tests - DNA tests ordered by healthcare professionals (2 links)
• ClinicalTrials.gov - Linking patients to medical research
• PubMed - Recent literature
• Online Books - Medical and science texts
• Scriver's Online Metabolic and Molecular Bases of Inherited Disease (OMMBID): Albinism
• OMIM - Genetic disorder catalog (5 links)

See How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about oculocutaneous albinism?

• See How can I find a genetics professional in my area? in the Handbook.
• Ask the Genetic and Rare Diseases Information Center.
• Submit your question to Ask the Geneticist.

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

• What does it mean if a disorder seems to run in my family?
• What are the different ways in which a genetic condition can be inherited?
• If a genetic disorder runs in my family, what are the chances that my children will have the condition?
• Why are some genetic conditions more common in particular ethnic groups?

These links provide additional genetics resources that may be useful.

• Genetics and health
• Resources for Patients and Families
• Resources for Health Professionals

What glossary definitions help with understanding oculocutaneous albinism?

albinism ; autosomal ; autosomal recessive ; cancer ; cell ; gene ; hypopigmentation ; involuntary ; melanin ; melanoma ; mutation ; nystagmus ; photophobia ; pigment ; pigmentation ; population ; recessive ; retina ; sensitivity ; sign ; symptom ; tissue ; Tyr

References

• Brilliant MH. The mouse p (pink-eyed dilution) and human P genes, oculocutaneous albinism type 2 (OCA2), and melanosomal pH. Pigment Cell Res. 2001 Apr;14(2):86-93. Review. PubMed citation
• Gene Review: Oculocutaneous Albinism Type 1
• Gene Review: Oculocutaneous Albinism Type 2
• Gene Review: Oculocutaneous Albinism Type 4
• Inagaki K, Suzuki T, Shimizu H, Ishii N, Umezawa Y, Tada J, Kikuchi N, Takata M, Takamori K, Kishibe M, Tanaka M, Miyamura Y, Ito S, Tomita Y. Oculocutaneous albinism type 4 is one of the most common types of albinism in Japan. Am J Hum Genet. 2004 Mar;74(3):466-71. Epub 2004 Feb 11. PubMed citation
• Oetting WS, Fryer JP, Shriram S, King RA. Oculocutaneous albinism type 1: the last 100 years. Pigment Cell Res. 2003 Jun;16(3):307-11. Review. PubMed citation
• Okulicz JF, Shah RS, Schwartz RA, Janniger CK. Oculocutaneous albinism. J Eur Acad Dermatol Venereol. 2003 May;17(3):251-6. Review. PubMed citation
• Rundshagen U, Zuhlke C, Opitz S, Schwinger E, Kasmann-Kellner B. Mutations in the MATP gene in five German patients affected by oculocutaneous albinism type 4. Hum Mutat. 2004 Feb;23(2):106-10. PubMed citation
• Sarangarajan R, Boissy RE. Tyrp1 and oculocutaneous albinism type 3. Pigment Cell Res. 2001 Dec;14(6):437-44. Review. PubMed citation
• Yi Z, Garrison N, Cohen-Barak O, Karafet TM, King RA, Erickson RP, Hammer MF, Brilliant MH. A 122.5-kilobase deletion of the P gene underlies the high prevalence of oculocutaneous albinism type 2 in the Navajo population. Am J Hum Genet. 2003 Jan;72(1):62-72. Epub 2002 Dec 5. PubMed citation