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Genetic and Rare Diseases Information Center (GARD)

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Ocular albinism type 1


Other Names for this Disease
  • Nettleship-Falls type ocular albinism
  • OA1
  • X-linked ocular albinism
  • X-linked recessive ocular albinism
  • XLOA
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Overview



What is ocular albinism type 1?

What causes ocular albinism type 1?

How is ocular albinism type 1 inherited? Are males or females more likely to be affected?


What is ocular albinism type 1?

Ocular albinism type 1 (OA1) is a genetic eye condition that primarily affects males. Signs and symptoms may include reduced coloring of the iris and retina (ocular hypopigmentation); foveal hypoplasia; rapid, involuntary eye movements (nystagmus); poor vision; poor depth perception; eyes that do not look in the same direction (strabismus); and increased sensitivity to light.[1][2] It is caused by mutations in the GPR143 gene and is inherited in an X-linked recessive manner.[1][2] Females have been affected in rare instances. Treatment consists of visual correction with eyeglasses or contact lenses; use of sunglasses or special filter glasses for light sensitivity; and in some cases, extraocular muscle surgery to restore alignment and/or improve a head posture that is associated with nystagmus.[2]
Last updated: 6/27/2013

What causes ocular albinism type 1?

Ocular albinism type 1 is caused by mutations in the GPR143 gene.[2] This gene provides instructions for making a protein that plays a role in pigmentation (coloring) of the eyes and skin. It helps control the growth of melanosomes, which are structures inside the cells that make and store a pigment called melanin. Melanin also plays a role in vision in the retina. Mutations in the GPR143 gene can affect the protein's ability to do its job. As a result, melanosomes in skin and retinal cell can grow abnormally large, contributing to the signs and symptoms of the condition.[1]
Last updated: 6/27/2013

How is ocular albinism type 1 inherited? Are males or females more likely to be affected?

Ocular albinism type 1 is usually caused by mutation in the GPR143 gene. In these cases, the condition is passed through families in an “X-linked” pattern.  In X-linked conditions males are more commonly affected than females. This is because males have only one X chromosome and therefore one copy of the GPR143 gene. Females have two X chromosomes and therefore two copies of the GPR143 gene. If females have a mutation in one of their GPR143 genes, they still have a second normal GPR143 gene to compensate. These women usually do not experience vision loss or other significant eye abnormalities. They may have mild changes in retinal pigmentation that can be detected during an eye examination.

 

Occasionally females will have more significant signs and symptoms of ocular albinism type 1. This may be due to:

  • A phenomenon called skewed X-chromosome inactivation 
  • Having inherited two mutations of the GPR143 gene 
  • Having a partial deletion of the X chromosome

To learn more about X inactivation please visit the following link. http://ghr.nlm.nih.gov/glossary=xchromosomeinactivation

Last updated: 3/31/2014

References
  1. Ocular albinism. Genetics Home Reference. 2007; http://ghr.nlm.nih.gov/condition=ocularalbinism. Accessed 7/24/2009.
  2. Gail Summers. X-linked recessive ocular albinism. Orphanet. April 2013; http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=54. Accessed 6/27/2013.
  3. Rosenberg T, Schwartz M. Ocular Albinism, X-Linked . GeneReviews. 2006; http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=x-oa. Accessed 7/24/2009.