A very characteristic feature of diastrophic dysplasia is the presence of soft cystic masses in the auricle during the neonatal period (Figure 155.1 [A]). Atlantoaxial instability may occur in these patients. These masses often become hypertrophic cartilage in early infancy. Radiographs of the distal limbs may show bone abnormalities (Figure 155.1 [B]). Diastrophic dysplasia is an autosomal recessive disorder. The gene maps to the distal long arm of chromosome 5.

A	B

Figure 155.1.— Diastrophic dysplasia. [A] Cystic auricular mass; [B] short, bent, and thick tubular bones.

Distal Arthrogryposis Syndrome
Neonates with distal arthrogryposis syndrome are usually fullterm and of average weight. They appear healthy. The face is usually not dysmorphic, although cases with cleft palate, cleft lip, small tongue, trismus, ptosis, and mild epicanthal folds have been described. The arthrogryposis involves the hands and, to a lesser extent, the feet. The cause of distal arthrogryposis syndrome is not known. A collagen abnormality leading to abnormal tendons has been considered. Arthrogryposis improves with time. Patients with distal arthrogryposis syndrome usually have normal intelligence. Distal arthrogryposis syndrome is an autosomal dominant condition with variable expression. The gene for distal arthrogryposis is in the pericentromeric region of chromosome 9.