Osteogenesis imperfecta (OI an sometimes known as Brittle Bone Disease) is a genetic bone disorder. People with OI are born without the proper protein (collagen), or the ability to make it, usually because of a deficiency of Type-I collagen. People with OI either have less collagen than normal or the quality is poorer than normal. As collagen is an important protein in bone structure, this impairment causes those with the condition to have weak or fragile bones.