Myositis ossificans, is the most common cause of heterotopic ossification usually within the large muscles. It exists in several forms, being benign in nature without malignant potential. Circumscripta subtype, is often post-traumatic. Fibrodysplasia ossificans progressiva is very rare subtype with heterotopic ossification starting between 2 and 5 years old and progressive in nature and fatal disease. Most cases arise from sporadic mutation and some other autosomal dominant inheritance pattern. ​