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