Fibrodysplasia ossificans progressiva Fibrodysplasia ossificans progressiva is a connective tissue disease that cause bone to form in muscle, tendons, ligaments, and other connecting tissue. This also causes your joints to become locked and permanently immobile. Fibrodysplasia ossificans progressiva is a very rare disease that it affects only one in two million people and there is only 800 known cases in the whole world. This disease is congenital, meaning this disease starts before birth, however the extra bone does not form before birth. It doesn’t matter what your race, ethnicity, or gender is, scientists don’t exactly know why people get this disease. So watch out, you may have it. There are many symptoms of Fibrodysplasia ossificans