Genetic Transmission of Fibrodysplasia Ossificans Progressiva: Report of Two Cases in a Family

Fibrodysplasia ossificans progressiva (FOP) is a rare connective tissue disorder characterized by congenital malformation of the great toes and by progressive heterotopic ossification of the tendons, ligaments, fasciae and skeletal muscles. We document the radiologic manifestation of FOP passed from a sporadically affected father to each of his two children (a son and a daughter). Previous consideration of a genetic etiology was based on the fact that the disease has been reported in several sets of monozygotic twins and that increased paternal age has been associated with sporadic occurrence of the disorder. Although autosomal-dominant transmission has long been suspected, the findings in this family provide confirmation for such inheritance and a basis for the diagnosis and counseling of patients with FOP.