[Fibrodysplasia ossificans progressiva. Apropos of a case]

Fibro-dysplasia ossificans progressive is a rare inherited disease, presumably transmitted as an autosomal dominant defect. The high level of spontaneous mutations explains the sporadic cases. Pre symptomatic diagnosis could be actually evoked by the association of progressive ossification of soft tissues with congenital anomalies of bones (metacarpal and metatarsal). The purpose of this study is to report a clinical case with a very severe course.

A 10-year-old boy developed progressive ossification of muscles and soft tissues in multiple sites neck, back, shoulders, elbows, hips and knees. The clinical course was severe due to the ankylosis of all the joints and the decrease of pulmonary reserve with fixation of the chest wall. A malformation of the great toes facilitated the diagnosis.

This pattern of heterotopic ossification together with the congenital malformations of the great toes defines the developmental phenotype for fibrodysplasia ossificans. A slow course with successive thrusts occurs. Ossification progressively involves tendons, ligaments and the connective tissue of skeletal muscles. Excision of heterotopic bone is futile as the trauma of the operation can lead to the stimulation of new heterotopic ossification at the operative site. Surgery is only useful for biopsy and histological study reveals bone metaplasia. The mature heterotopic bone is histologically indistinguishable from mature skeletal bone. The non skeletic muscles are characteristically spared from ossification. Premature death often results from respiratory failure due to fixation of the thoracic cage. The pathogenesis and the treatment of the disorder are unknown.