Regression of macular edema with topical brinzolamide and nepafenac alone and identification of a novel gyrate atrophy mutation / Regressão de edema macular com o uso tópico de brinzolamida e nepafenac e identificação de uma nova mutação na atrofia girata

ABSTRACT Gyrate atrophy is a rare metabolic autosomal recessive disorder caused by ornithine aminotransferase enzyme deficiency that leads to characteristic progressive, degenerative chorioretinal findings. Patients complain mostly of low vision, night blindness, and peripheral vision loss. Posterior subcapsular cataract, myopia, choroid neovascularization, and intraretinal cysts may be accompanying factors related to vision loss. We encountered a patient with vision loss secondary to posterior subcapsular cataract and intraretinal cysts. After treatment with topical brinzolamide and nepafenac (and without any diet mo dification and/or supplementation), we observed 143- and 117-mm macular thickness resolutions with 2 and 1 Snellen lines of visual gain in his right and left eyes, respectively. Also, we detected a novel homozygous mutation in the ornithine aminotransferase gene: c.1253T>C (p.Leu418Pro). Carbonic anhydrase inhibitors and/or non-steroid anti-inflammatory drugs can control macular edema in patients with gyrate atrophy-associated intraretinal cysts. The genetic variants may also be a determinant in the responsiveness to the therapy type.

RESUMO A atrofia girata é um distúrbio autossômico recessivo metabólico raro causado pela deficiência da enzima ornitina ami notransferase, que leva a achados degenerativos coriorretinianos progressivos característicos. Os pacientes queixam-se principalmente de baixa visão, cegueira noturna e perda de vi são periférica. A catarata subcapsular posterior, a miopia, a neovascularização da coróide e os cistos intrarretinianos podem ser fatores associados à perda da visão. Encontramos um paciente com perda de visão secundária à catarata subcapsular posterior e cistos intrarretinianos. Após o tratamento com brinzolamida tópica e nepafenaco (e sem modificação e/ou suplementação da dieta), observamos resoluções de espessura macular de 143 e 117 mm e com 2 e 1 linhas de Snellen de ganho visual nos olhos direito e esquerdo, respectivamente. Além disso, detectamos uma nova mutação homozigótica no gene da ornitina aminotransfera se: c.1253T>C (p.Leu418Pro). Inibidores da anidrase carbônica e/ou drogas anti-inflamatórias não esteróides podem controlar o edema macular em pacientes com cistos intrarretinianos associados à atrofia girata. As variantes genéticas também podem ser determinantes na responsividade ao tipo de terapia.

Gyrate Atrophy of the Choroid and Retina Diagnosed by Ornithine-delta-aminotransferase Gene Analysis: A Case Report

A pair of 19-year-old female identical twins was referred to our hospital with progressive visual loss. They exhibited bilateral chorioretinal atrophy involving the midperiphery on fundoscopy and fluorescein angiography. Bilateral visual field constriction was noted on dynamic Goldmann perimetry, and a markedly impaired response was observed on both photopic and scotopic electroretinograms. Cystoid macular edema was identified in both eyes on optical coherence tomography. Plasma levels of ornithine were elevated. Based on these observations, the patients were diagnosed with gyrate atrophy of the choroid and retina. The clinical diagnosis was confirmed by mutation analysis of the ornithine-delta-aminotransferase (OAT) gene. Patients were treated with a pyridoxine supplement (300 mg/day) and an arginine-restricted diet to lower plasma levels of ornithine, which were successfully reduced without progression of chorioretinal atrophy for 15 months. Our report describes the first case of gyrate atrophy in the Korean population diagnosed by OAT gene analysis and treated with vitamin B6 dietary supplementation.

A variant of ornithine aminotransferase from mouse small intestine

The ornithine aminotransferase (OAT) activity of mouse was found to be highest in the small intestine. The mitochondrial OAT from mouse small intestine was purified to homogeneity by the procedures including heart treatment, ammonium sulfate fractionation, octyl-Sepharose chromatography, and Sephadex G-150 gel filtration. Comparing to the amino acid sequence of mouse hepatic OAT, six N-terminal amino acid residues have been deleted in intestinal OAT. However, the subsequent sequence was identical with that of hepatic OAT. The molecular weights of both intestinal and hepatic OAT were estimated as 46 kDa by SDS-gel electrophoresis and as 92 kDa by gel filtration, indicating that both native OATs are dimeric. Biochemical properties of intestinal OAT, such as molecular weight, pH optimum and K(m) values for L-ornithine and alpha-ketoglutarate, were similar to those of hepatic OAT. However, intestinal OAT was more labile than hepatic OAT to tryptic digestion.