Osteogenesis Imperfecta (OI) or commonly known as Brittle Bone disorder is a group of disorders affecting the connective tissue and leading to weak, fragile bones and frequent fractures without any apparent impact like a fall. Like the name implies, OI refers to imperfect bone formation and structure.

Fibrodysplasia ossificans progressiva (FOP), is a rare autosomal dominant condition where the body’s soft tissues — muscles, ligaments, and tendons — turn into bone and form a second skeleton outside the normal one. FOP is the most disabling condition of ectopic skeletogenesis.