Partial regression of foveoschisis following vitamin B6 supplementary therapy for gyrate atrophy in a Chinese girl

Biochemical Studies on Human Ornithine Aminotransferase Support a Cell-Based Enzyme Replacement Therapy in the Gyrate Atrophy of the Choroid and Retina

The gyrate atrophy of the choroid and retina (GACR) is a rare genetic disease for which no definitive cure is available. GACR is due to the deficit of ornithine aminotransferase (hOAT), a pyridoxal 5'-phosphate-dependent enzyme responsible for ornithine catabolism. The hallmark of the disease is plasmatic ornithine accumulation, which damages retinal epithelium leading to progressive vision loss and blindness within the fifth decade. Here, we characterized the biochemical properties of tetrameric and dimeric hOAT and evaluated hOAT loaded in red blood cells (RBCs) as a possible enzyme replacement therapy (ERT) for GACR. Our results show that (i) hOAT has a relatively wide specificity for amino acceptors, with pyruvate being the most suitable candidate for ornithine catabolism within RBCs; (ii) both the tetrameric and dimeric enzyme can be loaded in RBC retaining their activity; and (iii) hOAT displays reduced stability in plasma, but is partly protected from inactivation upon incubation in a mixture mimicking the intracellular erythrocyte environment. Preliminary ex vivo experiments indicate that hOAT-loaded RBCs are able to metabolize extracellular ornithine at a concentration mimicking that found in patients, both in buffer and, although with lower efficiency, in plasma. Overall, our data provide a proof of concept that an RBC-mediated ERT is feasible and can be exploited as a new therapeutic approach in GACR.

Foveoschisis Associated With Gyrate Atrophy in Ornithine Aminotransferase Deficiency: A Case Report

Ornithine aminotransferase (OAT) deficiency is an autosomal recessive disease characterized by elevated serum ornithine levels caused by mutations in genes encoding for ornithine aminotransferase, a vitamin B6-dependent mitochondrial matrix enzyme. Gyrate atrophy (GA) is characteristic findings in OAT that characterized by sharply demarcated circular, pigmentary, brain-like areas of chorioretinal atrophy in the peripheral retina. This case report presents rare assosiation between OAT and GA and describes the characteristic imaging findings of this unique, not fully understood clinical entity. The coexistence of GA and foveoschisis is extremely rare in OAT deficiency. We report a case of foveoschisis in a patient with OAT, and we will discuss the possible mechanisms that lead to it. A 24-year-old male patient presented with complaints of decreased vision and nictalopia for 1 year. The patient, who was diagnosed with oat 6 years ago, had typical gyrate atrophy in his Fundus floresein angiography and foveoschisis in his Optical coherence tomography. He was diagnosed with gyrate atrophy and foveoschisis GA caused by OAT deficiency may present with macular involvement in the form of foveoschisis causing central visual impairment. Ophthalmologists should not ignore detailed fundus examination in children and young patients with visual impairment and should be aware of possible systemic diseases.

Regression of treatment-resistant gyrate atrophy-associated intraretinal cystic spaces using long-term diet restriction: A case report

PURPOSE

Gyrate atrophy of the choroid and retina (GA) is a rare genetic ophthalmologic condition which primarily manifests in childhood. It is characterized by hyperornithinemia and progressive chorioretinal atrophy. Patients may develop macular intraretinal cystic spaces (ICS) for which various treatment modalities have been reported. We report a patient who failed to demonstrate visual or anatomic improvement following multiple treatments for GA-associated ICS but showed improvement following prolonged dietary modification and vitamin supplementation.

CASE DESCRIPTION

A 6-year-old male patient presented with previously undiagnosed GA associated with ICS. He received 6 consecutive monthly intravitreal bevacizumab injections as well as topical nepafenac and dorzolamide for treatment of ICS without significant change detected by optical coherence tomography (OCT) following treatment. He was also maintained on an arginine restricted diet with vitamin B6 supplementation. Over the course of the ensuing year, the patient was lost to follow-up due to the coronavirus disease 2019 pandemic. When he returned, his vision was stable, and OCT showed regression of the ICS. His mother reported that he had continued only on dietary restriction and vitamin B6 supplementation with no other medications or interventions. Plasma ornithine level measurement confirmed dietary compliance. Further follow-up showed continued stabilization of the condition.

CONCLUSION

In addition to retarding progressive chorioretinal atrophy, prolonged dietary modifications may result in improvement of treatment-resistant GA-associated ICS. Parents' education on the value of dietary modifications for patients with GA is highly recommended.

[Gyrate atrophy of the choroid and retina with ornithinemia and foveoschisis (clinical observation)]

Gyrate chorioretinal atrophy (GCA) is a rare hereditary disease with certain complications; one extremely rare complication of GCA is foveoschisis. For the first time in Russian ophthalmology, a 10-year-old female child has been described to have genetically verified GCA associated with the OAT gene in combination with ornithinemia and foveoschisis. The diagnosis was made on the basis of fundus examination, perimetry data, autofluorescence, optical coherence tomography, fluorescence angiography, electroretinography, mass spectrometry with confirmation by molecular genetic research. The presented clinical case illustrates the need for an interdisciplinary approach to the diagnosis of GCA with diagnostic algorithm involving various examination methods and doctors of different specialties.

Gyrate Atrophy of the Choroid and Retina: A Review

Gyrate atrophy (GA) of the choroid and retina is a rare autosomal recessive genetic condition characterized by elevation of the plasma level of the amino acid ornithine due to deficiency of the enzyme ornithine ketoacid aminotransferase. Accumulation of ornithine occurs in various body tissues but leads primarily to characteristic ophthalmic manifestations including myopia, cataract, progressive chorioretinal atrophy, and macular changes. Patients usually present with night blindness that starts in the first decade of life followed by visual field constriction and eventually diminution of the central visual acuity and blindness. The condition has been reported worldwide and its differential diagnosis is broad and includes choroideremia and retinitis pigmentosa. Treatment currently depends on life-long dietary modifications including restriction of the amino acid arginine in diet. This article describes in detail the pathogenesis, clinical features, multimodal imaging findings, and treatment options for GA of the choroid and retina and its complications.