Abstract
Abstract: :
Purpose: In this study evaluates Gyrate Atrophy (GA) of the choroid and retina. This eases is a rare autosomic, recessive hereditary chorioretinal dystrophy due to deficiency in the mitochondrial matrix of the ornithine–delta–aminotransferase enzyme (OATase). Methods: Refrective errors, anterior biomicroscopy, aspect of fundus, Goldmann visual fields, maximal ERG responses, and ornithine levels have been studied in GA patients. Results: The cases presented and the cases analyzed clearly reveal that the aspect of the fundus and ocular tests in GA may appear within a widely varied context of ophthalmic, biochemical and genetic features. In our study, typical GA was observed in only one case. In the other three cases, we observed atypical findings such as hypermetropia and normal ornithinemia. Conclusions: In GA, the OATase is a piridofosfate–dependent mitochondrial enzyme present in many tissues among which the retina, that converts ketogluratate and ornithine into glutammate and semialdehyde glutammate, respectively. This absence means the accumulation of ornithine in body fluids with hyperornithinemia and ornithuria. Although the clinical phenotype is essentially confined to the ocular level, deficiency in OATase is a systemic disorder. The human genomic sequences responsible for GA are localized on the long arm of chromosome 10 (10q26) and on the short arm of chromosome (Xp11.2).Through the use of molecular biology techniques numerous mutations have been defined in the locus of the OATase in GA patients of different ethnic origins. The physiopatological mechanism responsible for chorioretinal degeneration of GA is still unknow. The theories proposed are centered on the possibility of direct toxic effects due to the high levels of ornithine within the mitochondria and focalized on the lack of creatine and proline at the retinal level. These studies suggest that myopia and hyperornithinemia are not costant features of Ga. In fact, the literature reports a wide number of clinical syndromes presenting a fundus culi that is similar to that typical of GA with hyper– or normal serum levels of ornithine. Occasionally, RP can be associated with moderate peripheral degeneration of the pebble type, so that the examiner diagnosis GA of the choroid and of the retina, RP usually manifests a decreased night vision and loss of lateral vision, symptoms that may be found in moderately advanced GA, too.
Keywords: retina • retinal degenerations: hereditary • proteins encoded by disease genes