A condition that imprisons its victims in a second skeleton may be one step closer to a treatment as a result of research at the University of Pennsylvania. Senior authors Eileen M. Shore, PhD, and Frederick S. Kaplan, MD, both of the Penn Department of Orthopaedic Surgery, and an international team of colleagues, have identified the gene that, when mutated, causes the disorder known as fibodysplasia ossificans progressiva (FOP). Their work is reported in the April 23 advanced online edition of Nature Genetics.

FOP is characterized by abnormal development of bone in parts of the body where bone is not normally present. Specifically, the disease causes skeletal muscles and soft connective tissue to be transformed into bone, locking joints into place and eventually making movement impossible.

Children with FOP seem normal at birth except for characteristic malformations of the big toe. During early childhood, these children may experience painful swellings that are often mistaken for tumors. As stiffness, pain, and limited movement progress, attempts to remove the extra bone may only lead to explosive growth of new bone.

Although FOP is an extremely rare condition affecting only an estimated 2,500 people worldwide, Dr. Kaplan believes the findings are relevant to every condition that affects bone formation. “FOP bone is perfectly normal in every way, except it should not be there,” he says.

The research was funded by the International FOP Association and National Institutes of Health. To read the news release and view images, go to www.uphs.upenn.edu/news.