Studies on retinitis pigmentosa in man. II. Erythrocyte osmotic fragility

The osmotic fragility of erythrocytes from patients with genetically classified forms of retinitis pigmentosa (RP) has been studied. The mean fragility was increased in autosomal dominantly inherited RP, where the dystrophy was expressed regionally in the retina, with both rods and cones affected. In contrast it was normal in patients with the dominantly inherited disease, which leads to a diffusely distributed dystrophy of, predominantly, rod photoreceptor cells. Raised osmotic fragility of erythrocytes has also been observed in female patients with multiplex (recessive) RP and in female carriers of the X-linked form of the disease.