Dominant mesomelic dysplasia, ankle, carpal, and tarsal synostosis type: a new autosomal dominant bone disorder.

A new type of mesomelic dysplasia was in 3 generations of a large Thai family. It is characterized by bilateral symmetrical marked shortening of the ulnae and shortening and bowing of the radii. The proximal fibula is usually short and synostoses are present between the tibia and fibula and the small malformed calcaneus and talus. The prominent calcanei on the ventral surfaces of the distal fibulae are a characteristic feature of the new type. Carpal and tarsal synostoses are present in some affected people. All affected individuals walk on the tips of their toes with the dorsal foot deviated laterally. The deformities of the radius and ulna somewhat resemble those of mesomelic dysplasia, Langer type, but otherwise the condition is distinctly different. This new mesomelic dysplasia is an autosomal dominant trait with complete penetrance and variable expressivity over 3 generations.