Ornithine aminotransferase deficiency (also known as gyrate atrophy of the choroid and retina) is an inborn error of ornithine metabolism, caused by decreased activity of the enzyme ornithine aminotransferase. Biochemically, it can be detected by elevated levels of ornithine in the blood. Gyrate atrophy of the choroid and retina, which is often shortened to gyrate atrophy, is an inherited disorder characterized by progressive vision loss. GYRATE ATROPHY (GA) of the choroid and retina (Figure 1) is a rare, autosomal recessive disease causing progressive chorioretinal degeneration resulting in.
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The clinical diagnosis can be confirmed by measuring serum or plasma ornithine levels; molecular confirmation can be obtained by mutational analysis of the OAT gyrate atrophy.
Occasionally, older patients present with an uncommon syndrome of peripheral chorioretinal atrophy that closely mimics gyrate atrophy; normal plasma ornithine gyrate atrophy in such patients exclude the diagnosis.
Although dietary restriction of gyrate atrophy has been used to treat some gyrate atrophy patients, the diet is very difficult to maintain and must be monitored by pediatricians with experience in metabolic disease.
Orphanet: Gyrate atrophy of choroid and retina
Almost all patients demonstrate impaired peripheral vision by age 10 years. Multiple efforts to treat GA have resulted gyrate atrophy conflicting reports, in part due to the difficulties in evaluating therapies for a rare, slowly progressing genetic disorder.
These variables, together with the small number of patients, make objective evaluation of therapeutic trials difficult. Inwe described the effects of long-term reduction of ornithine levels on the progression of the chorioretinal degeneration in Gyrate atrophy.
Siblings with autosomal recessive disorders like GA have identical genotypes at the disease gene gyrate atrophy and, on average, half of all of their genes are identical by descent.
The ratios of OAT with no PLP added were lowest for controls, intermediate for pyridoxine-nonresponsive heterozygotes, and highest for pyridoxine-responsive heterozygotes. The gyrate atrophy Km for PLP was lower in nonresponsive patients than in patients responsive to pyridoxine.
In 7 patients studied, the gyrate atrophy Km for ornithine was normal.
The patient with the mildest clinical disease, responsive to pyridoxine, had the most stable enzyme, but also the highest Km for PLP. OAT protein was clearly detectable gyrate atrophy Western blot analysis of mitochondrial proteins in the pyridoxine-responsive gyrate atrophy and in 2 of 5 nonresponders, but was low or undetectable in the 3 other patients.
No significant quantitative differences in OAT deficiency gyrate atrophy been found in cultured fibroblasts and lymphocytes from male and female patients. In both families, the younger sib in each pair, who was prescribed the diet gyrate atrophy an earlier age, demonstrated a slower progression of lesions compared with the older sib.
OMIM Entry - # - GYRATE ATROPHY OF CHOROID AND RETINA; GACR
They concluded that, if started at an early age, long-term substantial reduction gyrate atrophy plasma ornithine levels might appreciably slow the progression of the chorioretinal lesions and, to a lesser extent, the progressive loss of retinal function in patients with gyrate atrophy.
These individuals present with hyperammonemiapoor feeding, gyrate atrophy to thrive and increased excretion of orotic acid.
The enzyme, ornithine aminotransferase is coded for by the gene OAT, located at 10q