OSTEOGENESIS IMPERFECTA

hereditary disease of connective tissue that involves bone, sclera, inner ear, ligamentous structures, and skin. Several syndromes have been described, but they probably represent different degrees of expression of the same heritable disorder. The principal variants are osteogenesis imperfecta congenita, osteogeneis imperfecta tarda, and the van der Hoeve syndrome. In osteogenesis imperfecta congenita, still-birth is common, or fractures are evident at birth; severe crippling occurs as a result of numerous fractures, and survival to adulthood is uncommon. In osteogenesis imperfecta tarda, the infant is normal at birth, but, depending on the severity of disease, few or many fractures occur over the following years, usually as a result of trivial mishaps. The frequency of fractures tends to diminish after puberty. The van der Hoeve syndrome consists of osteogenesis imperfecta tarda, with bluish sclerae and deafness. The peculiar colour of the sclera is due to its abnormal thinness, which permits the pigmentation of the choroid (the middle coat of the eyeball) to show. Hearing loss may be due to deformities of the bones of the inner ear as well as to pressure on the auditory nerve because of deformity of its canal in the skull. Hyperextensibility of jointsdouble-jointednessand abnormally thin skin are also characteristic.