Fibrodysplasia ossificans progressiva is a rare and serious genetic disease that could have harmful and deadly results. A mutation of the body's repair mechanism causes fibrous tissue (including muscle, tendon and ligamnet) to be ossified  spontaneously or when damaged. A rare idiopathic or autosomal dominant MIM 135100 condition of irregular penetration and pre-pubertal onset, in which connective/interstitial tissues undergo extensive fibrosis and heterotopic ossification of ligaments, tendons, muscle, fascia, aponeuroses and skin, first seen in late childhood as firm masses. The abnormal development of bone may lead to stiffness in affected areas and may also limit movement in affected joints, e.g., knees, wrists, shoulders, spine, and/or neck. Fibrodysplasia ossificans progressiva (FOP) is a disorder in which muscle tissue and connective tissue such as tendons and ligaments are gradually replaced by bone (ossified), forming bone outside the skeleton (extra-skeletal or heterotopic bone) that constrains movement. This process generally becomes noticeable in early childhood, starting with the neck and shoulders and proceeding down the body and into the limbs.