The natural history of heterotopic ossification in patients who have

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fibrodysplasia ossificans progressiva. A study of forty-four patients. Cohen-R-B. Hahn-G-V. Tabas-J-A. Peeper-J. Levitz-C-L. Sando-A. Sando-N. Department of Orthopaedic Surgery, Hospital of the University of J-Bone-Joint-Surg-Am. 1993 Feb. 75(2). P 215-9. Forty-four patients who had fibrodysplasia ossificans progressiva responded by mail to a questionnaire regarding the age at the onset of heterotopic ossification at fifteen commonly involved anatomical sites. The average age of the patients when they responded to the questionnaire was twenty-seven years (range, three to sixty-nine years). The average age at the onset of ossification was five years (range, birth to twenty-five years). The most common sites of early heterotopic ossification were the neck, spine, and shoulder girdle. Thirty-five (80 per cent) of the patients had had some restrictive heterotopic ossification by the age of seven years. By the age of fifteen years, forty-two (more than 95 per cent) of the patients had severely restricted mobility of the upper limbs. In these patients, heterotopic ossification proceeded in a direction that was axial to appendicular, cranial to caudad, and proximal to distal; this pattern appeared typical for fibrodysplasia ossificans progressiva. Author-abstract.