Lethal osteochondrodysplasias: Praenatal and postnatal differential diagnosis.

Purpose: Lethal osteochondrodysplasias show an abnormal maturation and a di sturbed growth of cartilage and bones. They represent a heterogenous group of rare genetic diseases. Their incidence is 1 to 3 in 10000 births. Materi al and Methods: We report altogether 5 cases: two of thanatophoric dysplasi a, one of achondrogenesis type II and two cases of the rare fibrochondrogen esis. The differential diagnosis in respect to ultrasonographic, morphologi c, radiographic and histopathologic criteria of the most common of these di seases are discussed together with a review of the literature. Results: On the basis of the ultrasound finding of the short-rib-syndrome, it is possib le to differentiate between viable and lethal osteochondrodysplasias at 19 to 22 weeks of gestation. The short-rin-syndrome leads to pulmonary hypopla sia. Conclusions: It is essential to obtain an exact diagnosis postnatally by radiographic and histopathological examinations to counsel the parents c oncerning the risk of recurrency. The risk in this heterogenous group of ge netic diseases ranges between less than 1% up to 50% depending on the final diagnosis. Our two cases of fibrochondrogenesis in a consanguineous couple strongly suggest an autosomal recessive inheritance in this disease.