Oguchi Disease 2

A number sign (#) is used with this entry because of evidence that Oguchi disease-2 (CSNBO2) can be caused by homozygous mutation in the GRK1 gene (180381) on chromosome 13q34.

Description

Oguchi disease is a rare autosomal recessive form of congenital stationary night blindness in which all other visual functions, including visual acuity, visual field, and color vision, are usually normal. A typical feature of the disease is a golden or gray-white discoloration of the fundus that disappears in the dark-adapted state and reappears shortly after the onset of light (Mizuo phenomenon). The course of dark adaptation of rod photoreceptors is extremely retarded, whereas that of cones appears to proceed normally (summary by Fuchs et al., 1995).

For a general description and a discussion of genetic heterogeneity of Oguchi disease, see CSNBO1 (258100).

Clinical Features

Hayashi et al. (2007) reported 2 Japanese sibs, born of first-cousin parents, who had night blindness, 1.5 best-corrected visual acuity for each eye, normal color vision, and typical fundus appearance with golden-yellow discoloration. The visual fields were normal in 1 sib. The ERGs showed no rod B waves, reduced standard combined responses, and markedly reduced single-flash cone and 30-Hz flicker responses. Visual function in the sibs had not deteriorated with age, indicating that the disease was stationary.

Molecular Genetics

Individuals with Oguchi disease-1 (258100) have mutations in the gene encoding SAG (181031), also known as arrestin, a member of the rod phototransduction pathway. Because rhodopsin kinase works with arrestin in shutting off rhodopsin after it has been activated by a photon of light, Yamamoto et al. (1997) suspected that some cases of Oguchi disease might be caused by defects in the GRK1 gene. They analyzed the arrestin and rhodopsin kinase genes in 3 unrelated European patients with Oguchi disease previously reported by Carr and Gouras (1965) and by Carr and Ripps (1967). No defects in arrestin were detected, but all 3 cases had mutations in the GRK1 gene (e.g., 180381.0001).

Hayashi et al. (2007) reported the first Japanese patients with Oguchi disease who had a mutation in the GRK1 gene (180381.0004) rather than a mutation in the arrestin gene.