Mild expression of fibrodysplasia ossificans progressiva: a report of 3 cases.

We describe 3 unusually mild cases of fibrodysplasia ossificans progressiva (FOP) in an 80-year-old man, a 44-year-old woman, and a 17-year-old woman. The man, whose daughter had classic features of FOP, lacked malformation of the great toes and experienced unusually slow progression of the disease. Both women displayed late onset heterotopic ossification. The older women displayed an unusually slow progression of the disease. All 3 patients remained ambulatory at the time of examination. Recognition of a mild form of FOP will influence diagnosis, counselling, and research in this rare condition.