Skeleton of a man with fibrodysplasia ossificans progressiva (FOP). Plates and ribbons of ectopic bone can be seen directly on the skeleton.

Image Courtesy: © A.B. Shafritz et al., New Eng. J. Med., 335 (8): 555-61, 1996, Massachusetts Medical Society.
Skeleton part of collections at the Mütter Museum, College of Physicians of Philadelphia