Consideration of Rituximab for fibrodysplasia ossificans progressiva.

Fibrodysplasia ossificans progressiva (FOP) is a severe, progressive disease of the musculoskeletal system. Muscles, tendons and other connective tissues ossify after minor trauma, and patients often become encased in a second immobile skeleton. There is no known cure or treatment for FOP. It has been found that lymphocytes from FOP patients elaborate excess levels of bone morphogenic protein-4 (BMP-4). Given this, it has been suggested that allogenic bone marrow transplantation (BMT) possibly could be a cure for FOP, and drawn attention to a previously unappreciated case of an FOP patient who had successful BMT for aplastic anemia with apparent short- and medium-term arresting of the FOP disease process. However, BMT has non-trivial associated morbidity and mortality. Here, it is noted that if B cells are found to be the lymphocytes responsible for excess BMP-4 production in FOP, use of Rituximab, a monoclonal anti-CD20 antibody which effectively targets B cells, could be a less permanent and less risky treatment alternative for FOP.