Gyrate atrophy of the choroid and retina: Deficiency of ornithine aminotransferase in transformed lymphocytes

Gyrate atrophy of the choroid and retina is an inherited form of chorioretinal degeneration associated with hyperornithinemia. We measured the activity of ornithine aminotransferase (L-ornithine:2-oxo-acid aminotransferase, EC 2.6.1.13) in phytohemagglutinin-stimulated lymphocytes of a patient with gyrate atrophy and her daughter. The patient's cells had no detectable ornithine aminotransferase activity, and the activity in the heterozygote's cells was 44% of normal values. Measurements of [³H]thymidine incorporation and other transformation-affected enzymes verified that the patient's cells were transformed. These results demonstrate an enzyme deficiency in gyrate atrophy.