Prenatal diagnosis of osteogenesis imperfecta type II.

OBJECTIVE To characterize the prenatal sonographic features of osteogenesis imperfecta (OI) type II. DESIGN Descriptive (case series). SETTING Department of Obstetrics and Gynecology, Faculty of Medicine, Maharaj Nakorn Chiang Mai Hospital, Chiang Mai University. SUBJECTS Six fetuses with prenatal diagnosis of OI were evaluated. RESULTS Six fetuses were prenatally diagnosed as OI type II in five mothers without familial history of the disease. One mother had two consecutive pregnancies complicated with this condition. The first five cases were classified as OI type IIA, while the last one was OI type IIB. All of subtype A exhibited typical triad of bone shortening, diffuse hypomineralization and multiple fractures of long bones including beaded ribs whereas the subtype B showed shortening of only femurs, normal bone echodensity and isolated fractures of long bones. The postnatal radiography and autopsy confirmed the prenatal diagnosis in all cases. Other findings may occasionally be found, including polyhydramnios, oligohydramnios, hydrop fetalis and small for gestational age. CONCLUSION The triad of bone shortening, decreased bone density and numerous fractures including beaded ribs permits a confident diagnosis of OI type IIA. Furthermore, sonographic features may differentiate the subtype of OI type II, depending on degree of bone shortening and echodensity.