Gyrate Atrophy-Like Phenotype: Normal Plasma Ornithine and Retinal Crystals

Clinical characteristics of gyrate atrophy compared with a gyrate atrophy-like retinal phenotype

INTRODUCTION

Gyrate atrophy (GA) is a rare retinal dystrophy due to biallelic pathogenic variants in the ornithine aminotransferase (OAT) gene, causing a 10-fold increase in plasma ornithine levels. It is characterized by circular patches of chorioretinal atrophy. However, a GA-like retinal phenotype (GALRP) without elevated ornithine levels has also been reported. The aim of this study is to compare the clinical characteristics of GA and GALRP and to identify possible discriminators.

METHODS

A multicenter, retrospective chart review was performed at three German referral centres on patient records between 01/01/2009 and 31/12/2021. Records were screened for patients affected by GA or GALRP. Only patients with examination results for plasma ornithine levels and / or genetic testing of the OAT gene were included. Further clinical data was gathered where available.

RESULTS

Ten patients (5 female) were included in the analysis. Three suffered from GA, while seven had a GALRP. Mean age (± SD) at onset of symptoms was 12.3 (± 3.5) years for GA compared with 46.7 (± 14.0) years for GALRP patients (p = 0.002). Mean degree of myopia was higher in GA (-8.0 dpt. ± 3.6) compared to GALRP patients (-3.8 dpt. ± 4.8, p = 0.04). Interestingly, all GA patients showed macular oedema, while only one GALRP patient did. Only one patient with GALRP had a positive family history, while two were immunosuppressed.

DISCUSSION

Age of onset, refraction and presence of macular cystoid cavities appear to be discriminators between GA and GALRP. GALRP may encompass both genetic and non-genetic subtypes.

Gyrate atrophy-like phenotype with normal plasma ornithine and low plasma taurine

We present the case of a 39-year-old male with sectoral chorioretinal atrophy similar to that seen in gyrate atrophy (GA) but with a normal plasma ornithine level. Unlike previously reported cases of GA, he had below-normal plasma taurine concentration. Much remains unknown about the pathophysiologic mechanism underlying gyrate-like chorioretinal atrophy. The concomitant occurrence of GA-like phenotype and hypotaurinemia suggests a possible future avenue for research on this matter.