Fibrodysplasia ossificans progressiva: diagnosis and surgical management.

Fibrodysplasia (or Myositis) Ossificans Progressiva (FOP) is a rare genetic disease with variable expression, characterized by the association of congenital anomalies of the toes and fingers and progressive appearance of ectopic bone within the skeletal muscles, often following a trauma or an infection. FOP initially affects the nape and thoracic paravertebral muscles. With age, there is a progression of ossifications to other muscular groups following a proximodistal and cranio-caudal extension. Patients develop a restrictive respiratory insufficiency with atelectasis. The diagnosis of FOP is clinical and does not require biopsy. Circumscribed post-traumatic ossifying myositis is the most important differential diagnosis. It is characterized by the appearance of painful ossifications, in young adults, following a trauma and is limited to one localisation. The conservative treatment of FOP remains unsatisfactory. Surgical removal of osteomas to restore joint mobility leads to the development of additional heterotopic ossifications. Each surgical attempt brings about a quasi-inevitable recurrence. Anaesthesia of patients with FOP is difficult because of spinal rigidity and ankylosis of the jaw. Surgery is indicated only with a focused indication to correct an invalidating deformity.