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Oguchi Disease

The characteristics are congenital, static hemeralopia and diffuse yellow or gray coloration of the fundus. After 2 or 3 hours in total darkness, the normal color of the fundus returns. The condition is more frequent in Japanese. See hemeralopia (310500) for a comment on the use of this term, as opposed to the term nyctalopia.

Maw et al. (1995) referred to Oguchi disease as a rare autosomal recessive form of congenital stationary night blindness, associated with fundus discoloration and abnormally slow dark adaptation. A plausible candidate gene for Oguchi disease is that encoding S antigen, also known as arrestin (SAG; 181031). This gene encodes a 48-kD protein that may be involved in the recovery phase of light transduction (Palczewski et al., 1989; Palczewski et al., 1992). The SAG gene had been previously been mapped to 2q37.1 by fluorescence in situ hybridization. Maw et al. (1995) found linkage of Oguchi disease to markers that mapped to distal 2q in an inbred Indian kindred. The segregation data suggested that 3 affected sisters were homozygous by descent for a region between D2S172 and D2S345. An intragenic SAG polymorphism was homozygous in all affected persons and a recombination event suggested that SAG maps proximal to D2S345. Collectively, the finding supported the suggestion that a defect in S antigen is responsible for Oguchi disease.

Because the arrestin gene maps to the same region of 2q as Oguchi disease and because it encodes a rod photoreceptor implicated in the recovery phase of light transduction, SAG was a candidate gene for the site of the mutation in this disorder. Fuchs et al. (1995) identified a homozygous deletion in 5 of 6 unrelated Japanese patients with Oguchi disease (181031.0001).

Because rhodopsin kinase (RHOK; 180381) works with arrestin in shutting off rhodopsin after it has been activated by a photon of light, it was reasonable to propose that some cases of Oguchi disease may be caused by defects in rhodopsin kinase. Yamamoto et al. (1997) analyzed the arrestin and rhodopsin kinase genes in 3 unrelated cases of Oguchi disease. No defects in arrestin were detected, but all 3 cases had mutations in the RHOK gene (e.g., 180381.0001).

CLINICAL SYNOPSIS

Eyes :
Static hemeralopia
Congenital hemeralopia
Yellow fundus
Gray fundus

Inheritance :
Autosomal recessive

 


Source: http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?258100#TEXT


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