Multimodal characterization of a novel mutation causing vitamin B6-responsive gyrate atrophy

Purpose: Gyrate atrophy (GA) is a rare chorioretinal degeneration that results in the deterioration of night and peripheral vision, eventually leading to blindness. The disorder is caused by mutations in the gene encoding ornithine aminotransferase (OAT), causing increased levels of plasma ornithine. Treatment revolves around lowering plasma ornithine levels, with vitamin B6 supplementation being the preferred treatment. Nevertheless, most patients do not respond to this therapy. Here, we report a rare case of vitamin B6-responsive GA caused by a novel mutation in OAT and characterize the presentation with multimodal imaging.

Methods: This is a single-patient case report with a clinical diagnosis based on history, multimodal retinal imaging, laboratory findings, and DNA sequencing analysis. We include a 3D structure prediction of the novel mutant protein.

Results: DNA sequencing analysis demonstrated that there is a homozygous, novel variant c.473A>C: p.Y158S in OAT. Upon undergoing two weeks of vitamin B6 supplementation, the patient exhibited a 28.5% reduction in plasma ornithine levels. In a follow-up visit two years later, plasma ornithine levels were reduced by 24.1% from the levels at initial presentation and disease progression was retarded based on clinical findings.

Conclusion: One novel homozygous missense mutation in OAT was identified and considered to be pathogenic in a patient with GA. The response for the vitamin B6 supplementation was positive, which is rare in all the GA cases reported in the literature. Our data suggests that further studies regarding the relationship between genotype and responsiveness to vitamin B6 should be conducted.