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Leber Congenital Amaurosis

Inherited retinal degenerative disorder

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Updated July 15, 2005

Leber congenital amaurosis is an inherited retinal degenerative disorder that causes an infant to be born with severely impaired vision. It is inherited in an autosomal recessive manner, meaning that both parents must carry a defective gene for their child to be born with the disorder. Leber congenital amaurosis and early-onset retinitis pigmentosa are estimated to affect 3 in 100,000 newborns.

Symptoms
Infants born with Leber congenital amaurosis have severely impaired vision. They also are born with, or develop, roving or jerking involuntary eye movements (nystagmus). Children with the disorder may poke their eyes or press on them with their fists or fingers. This may lead to misshapen and thinned corneas (keratoconus), cataracts, and a sunken appearance of the eyes.

The appearance of the retinas may change with age but once childhood is past, vision usually remains stable. The individual with Leber congenital amaurosis may only have vision at the level of seeing light and dark or detecting hand motions.

Diagnosis
It may be difficult to differentiate Leber congenital amaurosis from early-onset retinitis pigmentosa or from syndromes that cause impaired vision. It is also hard to distinguish what is vision and what is behavior in an infant or very young child. Therefore, electroretinography (ERG) testing is important in measuring if the child can see, and how much. In Leber congenital amaurosis, the ERG usually detects little activity in the retinas.

Treatment
There is no specific treatment for Leber congenital amaurosis. Individuals with the disorder may benefit from the use of low-vision aids if they have enough vision.

Research working on prevention
A number of gene mutations have been identified as being associated with Leber congenital amaurosis. Researchers are working on developing methods, such as replacement of the defective gene with a normal one, which might prevent the disorder and the severe vision loss. A multi-institutional group of researchers used gene therapy to restore vision to a dog whose eye disease mimicked human Leber congenital amaurosis caused by mutations in the RPE65 gene. Phase I trials of this type of gene therapy are scheduled to begin in fall 2005.

Another gene, AIPL1, is the focus of research at St. Jude Children’s Hospital in Memphis, Tennessee, and Columbia University. Scientists there have developed a laboratory mouse with Leber congenital amaurosis that is missing both copies of the AIPL1 gene, and are using the mouse model to develop a gene therapy to prevent the disorder. The research is providing insights into how the retina degenerates and causes the loss of sight.

Information for this article was taken from:
- Foundation Fighting Blindness. Leber congenital amaurosis.
- Contact a Family. Leber’s congenital amaurosis.
- Iannaccone, A. (2005). The genetics of hereditary retinopathies and optic neuropathies. Comprehensive Ophthalmology Update, 6(1), pp. 39-62.
- Latkany, P. New developments in retinal disease. American Academy of Ophthalmology 2004 Annual Meeting, accessed at http://www.medscape.com/viewarticle/494566.
- St. Jude Children’s Hospital. New model of rare childhood blindness holds promise for testing preventive therapies. Press release dated 12/13/2004.

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