Lethal osteopetrosis with multiple fractures in utero.

Severe osteopetrosis was diagnosed in utero in two successive pregnancies resulting from an intermarriage. Hydrocephaly and skeletal hyperdensity were detected at 18 weeks of gestation, and fractures at 24 weeks. We report on extensive ultrasound, radiological, and pathological findings, including those on brain and bone. The markedly reduced number of osteoclasts observed in these sibs and the very early fetal involvement suggest that this form of osteopetrosis might represent a new entity: autosomal recessive lethal osteopetrosis.