Multimodal imaging and genetic screening in Mexican patients with Gyrate atrophy: identification of novel OAT pathogenic variants.

Purpose: Description of retinal phenotype by structural and functional testing, ornithine plasma levels and mutational data of OAT gene in patients with Gyrate Atrophy (GA).

Methods: Ophthalmologic examination, fundus photography (CFP), autofluorescence (FAF), spectral-domain optical coherence tomography (SD-OCT), Goldmann perimetry (GP), full-field electroretinogram (ffERG) and chromatic perimetry (CP) testing were performed. Ornithine plasma levels were measured. Sanger sequencing mutational analysis of the coding exons and exon-intron junctions of the OAT gene were analyzed.

Results: Twelve eyes of seven Mexican patients with GA were included. CFF showed peripheric patches of chorioretinal atrophy; FAF revealed peripheric oval areas of hypoautofluorescence; SD-OCT exhibited outer retinal tubulations in 58%, cystoid macular edema in 50%, epiretinal membrane in 42%, foveoschisis and staphyloma in 17%, and hyperreflective deposits in 100% of the eyes; GP showed constricted visual fields in 100% of the eyes; ffERG revealed preserved photopic response in 17% and preserved scotopic response in 17% of the eyes; CP exposed a deficit in generalized response of rods and cones in 100% of the eyes. Mean ornithine plasma levels were 509.5 µmol/L. One patient with genetic confirmation of GA had normal ornithine plasma levels (48 µmol/L). Molecular findings in OAT gene detected two novel pathogenic variants: c.796 C > T (p.Gln266*) and c.721_722dupCC (p.Asp242ArgfsTer6).

Conclusion: This study provides new information regarding functional and structural diagnosis in patients with GA, expands the understanding of retinal phenotype in patients with GA, reports two novel mutations and presents the first case of GA confirmed by genetic testing with normal ornithine levels.