Clinical and biochemical heterogeneity in gyrate atrophy.

Two patients had milder variants of the usual form of gyrate atrophy. Although the appearance of the chorioretinal degeneration was identical, the progression of the clinical signs and symptoms were slower with night blindness, cataracts, and decreased vision occurring at an older age. Additionally, the level of hyperornithinemia, although still increased above normal, was lower than that usually found in such patients (between 448 and 676 microM). Additionally, one of our patients responded to high dosage vitamin B6 with a 27% reduction in plasma ornithine. The difference in the quantitation of the increase in plasma ornithine, the difference in responsiveness to vitamin B6, and the difference in the clinical consequences of this underlying biochemical abnormality, indicated a variant form of gyrate atrophy, suggesting the presence of genetic heterogeneity.