Abstract
A review of the radiographs of children previously classified as achondroplasiacs revealed six thanatophoric dwarfs. The main radiological differentiating features were the greater degree of shortening of the long bones, including the fibula, the curvature of the femora, the very small size of the thorax and, particularly, the very narrow ossified elements of the vertebral bodies. Perhaps the most important aspect of differential diagnosis lies in recognition in utero. The reported association with clover-leaf deformity of the skull in sibs provides the strongest evidence for genetic differentiation from classical achondroplasia. More evidence might be obtained by a widespread search through hospital radiological museums.