Study of a father and son who had helicoid peripapillary chorioretinal degeneration suggests that a progressive tearing and retraction of the retinal pigment epithelium or of Bruch's membrane around the optic disk may be involved in the disorder's pathogenesis. We presume that this tearing results primarily from dysplastic abnormalities of the retinal pigment epithelium that surrounds the optic disk. The dystrophic lesions progress slowly and may affect the macula and even the peripheral retina.