Hyperornithinaemia and gyrate atrophy of the retina: improvement of vision during treatment with a low-arginine diet.

A 15-year-old patient with hyperornithinaemia (0.6--1.2 mmol/l) and gyrate atrophy of the retina was given a low-arginine diet to reduce plasma ornithine to a concentration (0.15--0.25 mmol/l) near the normal range. After five weeks of treatment, there was improvement in the visual function of one eye which had been severely impaired without improvement for 3 years. This improved visual function was maintained until compliance with the diet deteriorated at eight months, after which visual function regressed towards pretreatment status. Overrestriction of dietary arginine produced hyperammonaemia, indicating that arginine is an essential aminoacid in ornithine transaminase deficiency. These results suggest that reduction of plasma ornithine may reverse a metabolic neuroretinopathy in this disease, and offer hope that progression of the retinal atrophy can be arrested as well.