Ocular Albinism

Ocular Albinism

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Ocular Albinism is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • OA1
  • XLOA
  • Nettleship-Falls ocular albinism
  • ocular albinism type 1
  • X-linked ocular albinism

Disorder Subdivisions

  • X-linked congenital nystagmus 6 (NYS6)

General Discussion

Ocular albinism type 1 (OA1), or X-linked ocular albinism, is the most common form of ocular albinism. Ocular albinism is a genetic disorder characterized by vision abnormalities in affected males. Vision deficits are present at birth and do not become more severe over time. Affected individuals have normal skin and hair pigmentation. Ocular albinism is inherited as an X-linked recessive genetic condition and caused by mutations in the G protein-coupled receptor 143 (GPR143) gene.

Symptoms

Ocular albinism primarily affects the eyes. Several vision problems can occur with ocular albinism including an involuntary movement of eyes back and forth (nystagmus), reduced iris pigment in some individuals, reduced retinal pigment, lack of development of the fovea (foveal hypoplasia) leading to blurred vision, and abnormal connections in the nerves from the retina to the brain that prevents the eyes from tracking together and reduces depth perception. Crossed eyes (strabismus) and sensitivity to light are also common. Typically individuals have normal hair and skin pigmentation.



Congenital motor nystagmus is a genetic condition characterized by an involuntary movement of eyes back and forth (nystagmus). Affected individuals will often turn or bob their head to try to improve vision clarity. Pigmentation in the eye is normal. There is preliminary evidence that some mutations of GPR143 result in X-linked congenital nystagmus in males. This has been seen in several different Chinese families. Affected males have congenital nystagmus but they do not have the additional changes typically seen in individuals with classical X-linked ocular albinism including a reduction in retinal pigmentation and pathological changes to the fundus. Female carriers appear to be unaffected. Further research needs to be done to understand how mutations in the same gene can result in different outcomes.

Causes

Mutations in the G protein-coupled receptor 143 (GPR143) gene on the X chromosome cause ocular albinism type 1 (OA1). This protein is found in the retinal pigment epithelium of the eye and is thought to be involved in signaling within the pigment cell to regulate melanin pigment production. This protein also interacts with the premelanosomal protein MART1 which also is part of the regulation of melanin pigment formation. Mutations in GPR143 result in a decrease in melanin pigment production and enlarged aberrant premelanosomes which is the intracellular location of pigment production in the pigment cell.



Ocular albinism is inherited as an X-linked recessive genetic condition. X-linked recessive genetic disorders are conditions caused by an abnormal gene on the X chromosome. Females have two X chromosomes but one of the X chromosomes is "turned off" and most of the genes on that chromosome are inactivated. Females who have a disease gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms of the disorder because inactivation of the X chromosome is random and usually half of the cells in the eye have the normal X chromosome activated resulting in normal vision. A male has one X chromosome and if he inherits an X chromosome that contains a disease gene, he will develop the disease. Males with X-linked disorders pass the disease gene to all of their daughters, who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome instead of their X chromosome to male offspring. Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease, and a 25% chance to have an unaffected son.

Affected Populations

The prevalence of ocular albinism has been reported to be one male in 20,000 births.

Standard Therapies

Diagnosis

The diagnosis of ocular albinism is based on the characteristic eye findings. Female relatives who carry the gene for ocular albinism will have retinal pigment abnormalities. Molecular genetic testing for GPR143 gene detects mutations in approximately 90% of affected males and is available to confirm the diagnosis.



Treatment

Individuals diagnosed with ocular albinism should be evaluated by an ophthalmologist at the time of diagnosis to determine the extent of the disease and have ongoing ophthalmologic examinations annually. Glasses or contact lenses can greatly improve vision. Dark glasses or a hat with a brim can help to reduce sun sensitivity.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.



For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:



Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov



For information about clinical trials sponsored by private sources, contact:

www.centerwatch.com

References

TEXTBOOKS

King RA, Hearing VJ, Creel DJ, et al. Albinism. In: Scriver CR, Beaudet AL, Sly WS, Valle D (eds) The Metabolic and Molecular Basis of Inherited Disease. New York, NY: McGraw-Hill; 2001:5587-627.



King RA, Oetting WS, Summers CG, et al. Abnormalities of pigmentation. In: Rimoin DL, Connor JM, Pyritz RE, Korf BR (eds) Emery and Rimoin's Principles and Practice of Medical Genetics, 4th ed. London: Harcourt; 2001.



JOURNAL ARTICLES

Hu J, Liang D, Xue J, Liu J, Wu L. A novel GPR143 splicing mutation in a Chinese family with X-linked congenital nystagmus. Mol Vis. 2011;17:715-22.



Peng Y, Meng Y, Wang Z, et al. A novel GPR143 duplication mutation in a Chinese family with X-linked congenital nystagmus. Molec. Vis. 2009;15:810-814.



Camand O, Boutboul S, Arbogast L, et al. Mutational analysis of the OA1 gene in ocular albinism. Opthalmic Genet. 2003;24:167-73.



Oetting WS. New Insights into ocular albinism type 1 (OA1): Mutations and polymorphisms of the OA1 gene. Hum Mutat. 2002;19:85-92.



Bassi MT, Bergen AA, Bitoun P, et al. Diverse prevalence of large deletions within the OA1 gene in ocular albinism type 1 patients from Europe and North America. Hum Genet. 2001;108:51-4.



Charles SJ, Green JS, Grant JW, et al. Clinical features of affected males with X-linked ocular albinism. Br J Opthalmol. 1993;77:222-7.



INTERNET

Lewis RA. (Updated April 5, 2011). Ocular Albinism, X-linked. In: GeneReviews at GeneTests: Medical Genetics Information Resource (database online). Copyright, University of Washington, Seattle. 1997-2011. Available at http://www.genetests.org. Accessed April 24, 2012.



Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Albinism, Ocular, Type 1; OA1. Entry No: 300500. Last Edited June 16, 2011. Available at: http://www.ncbi.nlm.nih.gov/omim/.Accessed April 24, 2012.

Resources

National Organization for Albinism and Hypopigmentation

PO Box 959

East Hempstead, NH 03826-0959

Tel: (603)887-2310

Fax: (800)648-2310

Tel: (800)473-2310

Email: noah@albinism.org

Internet: http://www.albinism.org



March of Dimes Birth Defects Foundation

1275 Mamaroneck Avenue

White Plains, NY 10605

Tel: (914)997-4488

Fax: (914)997-4763

Tel: (888)663-4637

Email: Askus@marchofdimes.com

Internet: http://www.marchofdimes.com



Albinism Fellowship

P.O. Box 77

Burnley

Lancashire, BB11 5GN

United Kingdom

Tel: 07919543518

Tel: 447919543518

Email: support@albinism.org.uk

Internet: http://www.albinism.org.uk



NIH/National Institute of Child Health and Human Development

31 Center Dr

Building 31, Room 2A32

MSC2425

Bethesda, MD 20892

Fax: (866)760-5947

Tel: (800)370-2943

TDD: (888)320-6942

Email: NICHDInformationResourceCenter@mail.nih.gov

Internet: http://www.nichd.nih.gov/



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/



Madisons Foundation

PO Box 241956

Los Angeles, CA 90024

Tel: (310)264-0826

Fax: (310)264-4766

Email: getinfo@madisonsfoundation.org

Internet: http://www.madisonsfoundation.org



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into myCigna.com. For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html.

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