Inborn Errors of Metabolism: Gyrate Atrophy.

Gyrate atrophy is an autosomal recessive dystrophy in which night blindness starts early in the first decade of life. In the early stages, large areas of retinal pigment epithelium (RPE) and choriocapillaris (CC) atrophy in the far periphery (lobular shape, Fig. 37.1). (In choroideremia, atrophy appears in the mid periphery.) Later, these areas coalesce to form a characteristic scalloped border at the junction of healthy and diseased RPE. Myopia and subcapsular cataract are common by the end of second or third decade. Unlike in choroideremia (which is X-linked), patients with gyrate atrophy show areas of hyperpigmentation of the remaining RPE (Fig. 37.2). Patients with gyrate atrophy do not show the choroidal atrophy (as seen in choroideremia) until the late stages. Treatment includes a low-protein, arginine-restricted diet for all patients. In some cases, vitamin B6 (pyridoxine) may help in lowering plasma ornithine levels.