Oculocutaneous Albinism

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This entry is adapted from the peer-reviewed paper https://medlineplus.gov/genetics/condition/oculocutaneous-albinism

Oculocutaneous albinism is a group of conditions that affect coloring (pigmentation) of the skin, hair, and eyes.

genetic conditions

1. Introduction

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).

Researchers have identified multiple types of oculocutaneous albinism, which are distinguished by their specific skin, hair, and eye color changes and by their genetic cause. 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.

Several additional types of this disorder have been proposed, each affecting one or a few families.

2. Frequency

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.

3. Causes

Oculocutaneous albinism can result from mutations in several genes, including TYR, OCA2, TYRP1, and 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. Mutations in additional genes likely underlie the other forms of this disorder. The genes associated with oculocutaneous albinism 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.

Some individuals with oculocutaneous albinism do not have mutations in any of the known genes. In these people, the genetic cause of the condition is unknown.

4. Inheritance

Oculocutaneous albinism is inherited in an autosomal recessive pattern, which means both copies of a 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 they do not show signs and symptoms of the condition.

5. Other Names for This Condition

albinism, oculocutaneous
OCA

References

Brilliant MH. The mouse p (pink-eyed dilution) and human P genes,oculocutaneous albinism type 2 (OCA2), and melanosomal pH. Pigment Cell Res. 2001Apr;14(2):86-93. Review.
Grønskov K, Ek J, Brondum-Nielsen K. Oculocutaneous albinism. Orphanet J Rare Dis. 2007 Nov 2;2:43. Review.
Hayashi M, Suzuki T. Oculocutaneous Albinism Type 4. 2005 Nov 17 [updated 2017Sep 7]. In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K,Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University ofWashington, Seattle; 1993-2020. Available fromhttp://www.ncbi.nlm.nih.gov/books/NBK1510/
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. Oculocutaneousalbinism type 4 is one of the most common types of albinism in Japan. Am J HumGenet. 2004 Mar;74(3):466-71.
Kamaraj B, Purohit R. Mutational analysis of oculocutaneous albinism: acompact review. Biomed Res Int. 2014;2014:905472. doi: 10.1155/2014/905472.
Lewis RA. Oculocutaneous Albinism Type 1. 2000 Jan 19 [updated 2013 May 16].In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington,Seattle; 1993-2020. Available from http://www.ncbi.nlm.nih.gov/books/NBK1166/
Lewis RA. Oculocutaneous Albinism Type 2. 2003 Jul 17 [updated 2012 Aug 16].In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington,Seattle; 1993-2020. Available from http://www.ncbi.nlm.nih.gov/books/NBK1232/
Montoliu L, Grønskov K, Wei AH, Martínez-García M, Fernández A, Arveiler B,Morice-Picard F, Riazuddin S, Suzuki T, Ahmed ZM, Rosenberg T, Li W. Increasingthe complexity: new genes and new types of albinism. Pigment Cell Melanoma Res.2014 Jan;27(1):11-8. doi: 10.1111/pcmr.12167.
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.
Rundshagen U, Zühlke C, Opitz S, Schwinger E, Käsmann-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.
Sarangarajan R, Boissy RE. Tyrp1 and oculocutaneous albinism type 3. PigmentCell Res. 2001 Dec;14(6):437-44. Review.
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 highprevalence of oculocutaneous albinism type 2 in the Navajo population. Am J HumGenet. 2003 Jan;72(1):62-72.

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Rita Xu

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Table of Contents

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1. Introduction

2. Frequency

3. Causes

4. Inheritance

5. Other Names for This Condition

References

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1. Introduction

2. Frequency

3. Causes

3.1. The Genes Associated with Oculocutaneous Albinism

3.1.1. Additional Information from NCBI Gene

4. Inheritance

5. Other Names for This Condition

References