The phenotypic features of osteogenesis imperfecta resulting from a mutation of the carboxyl-terminal pro alpha 1 (I) propeptide that impairs the assembly of type I procollagen and formation of the extracellular matrix.

The features of a baby with lethal perinatal osteogenesis imperfecta (OI-II), resulting from the substitution of tryptophan 94 by cysteine in the carboxyl-terminal propeptide of pro alpha 1 (I) chains of type I procollagen, were studied. The limbs and torso were of normal length, shape, and proportion. Similarly, all bones were of relatively normal shape and the long bones showed normal metaphyseal modelling. These clinical and radiographic features were similar to those observed in another baby with OI-II resulting from a mutation of the carboxy-terminal propeptide of pro alpha 1 (I) chains but dissimilar from those reported in babies with OI-II resulting from helical mutations of type I collagen.