The case of a 19-year-old female patient with myositis ossificans progressiva is reported. This disease is a rare hereditary disorder with a dominant autosomal genotype. The patient had typical ossifications of the humeral and dorsal muscles, as well as of those of the left thigh and upper arm, and also an ankylosis of the left hip. There were typical deformations of the cervical vertebrae and of the skeleton of the hands and feet. Laboratory tests showed alkaline phosphatase to be greatly increased. ECG revealed a bifascicular bundle-branch block, and a high-grade restrictive ventilation disorder was shown up by pulmonary function test. When the stability of the genetic material was investigated, DNA synthesis was found to be normal, DNA repair was slightly accelerated, and the sister chromatid exchange rate following stimulation with mitomycin C was higher than in controls.