Insight into the role that abnormal Hedgehog signaling may have in the histogenesis of retinal dysplasia has come from studies of Ptch. Ptch mutations cause Gorlin syndrome, an autosomal dominant disorder characterized by dental, skeletal and radiographic abnormalities including falx calcification, bifid/fused ribs and altered vertebral segmentation, and a predisposition to tumor development including early-onset basal cell carcinomas [39-44]. This evidence concerns the gene PTCH1 and nevoid basal cell carcinoma syndrome.