osteogenesis imperfecta type ii

diagnosis

osteogenesis type ii has been diagnosed successfully prior to 20 weeks gestation. in type iia is there is bone shortening, diffuse hypomineralization and multiple fractures. there are short, thick, beaded ribs and a small chest. the long bones are crumpled (accordion-shaped), short and broad. vertebrae are flattened, with broad round ilia and broad pubic bones. the facial bones and cranial vault are very poorly ossified. at birth, infants are small for gestational age and often premature. they have blue/black sclerae and marked moulding of the face and cranium. twenty percent are stillborn, and of the remainder, only 10% are alive at 1 month. type ii a is probably the result of a new dominant mutation. type iib is characterized by shortening of the femur alone, mainly normal bone density and isolated fractures. there is patchy mineralisation of the skull, and the ribs are thin and wavy without beading or fractures. the femurs are short, broad and crumpled, while the tibiae are thickened and angulated. vertebral bodies are of a more normal height than in type iia. the mean gestational age at birth is 37 weeks and the mean survival 14 hours. inheritance is believed to be autosomal dominant, with parental germ cell mosaicism accounting for observed sibling recurrences. type iic is thought to be autosomal recessive in its inheritance. there is marked hypo-ossification of the skull. long bones are slender with inadequately modelled shafts, angulation deformities and numerous fractures. the ribs are slender and beaded, although less uniformly than in type iia.