Thanatophoric dysplasia. A report of three cases.

Thanatophoric dysplasia is an osteochondrodysplasia always lethal already in the neonatal period. Three cases, showing the characteristic X-ray picture of the disease, are described. Histopathologically, an abnormality in the endochondral ossification process was observed. In sections from tubular bones the growth zone was found to be irregular with deficient chondrocyte maturation, absence of orderly chondrocyte columns, and the development of coarse bone trabeculae. Moreover, prominent subperiostal bone formation could be demonstrated. A constant finding was also a fibrous band, continuous with the periosteum/perichondrium, and extending into the growth zone. From this fibrous tissue membranous bone formation, directed towards the metaphysis and appearing to add to bone length, was observed. It seems as if direct bone formation predominates in thanatophoric dysplasia.