Clinical Manifestations. Posterior shortening of the thorax and thoracolumbar lordosis are the major causes of short stature. The neck is short and often nearly immobile, and the head appears to rest on the shoulders. The limbs are long in relation to the trunk. The barrel chest bulges anteriorly, the lower anterior ribs may infringe on the iliac crests, and the abdomen protrudes. Recurrent respiratory infections are common and may be related to the chest deformity, pulmonary hypoplasia, or cor pulmonale. Laryngotracheomalacia is an uncommon feature.

Radiographic Findings. Severe vertebral abnormalities—hemivertebrae, fused (block) vertebrae, absent and butterfly vertebrae—characterize this disorder. The ribs are reduced in number, and the posterior costovertebral articulations may be bizarrely approximated, producing a fanlike radiation of ribs. The posterior shortening of the spine causes anterior flaring of the chest and deformity of the rib cage. No significant abnormalities are seen in the appendicular skeleton or skull.

DYGGVE-MELCHIOR-CLAUSEN DYSPLASIA

Dyggve-Melchior-Clausen dysplasia is a rare and unusual disorder with an autosomal recessive inheritance.

Clinical Manifestations. Recognizable as early as 6 to 12 months of age, this disorder results in short-trunk dwarfism with a short neck, exaggerated lumbar lordosis, scoliosis, and prominent interphalangeal joints of the fingers with mild contractures and claw hand. Mental retardation and speech delay are common but not invariable. Adult height is about 52 inches.

Radiographic Findings. Radiographs reveal a generalized platyspondyly that usually persists into adulthood. In childhood, lateral views show anterior pointing of the vertebral bodies, with broad notches in the superior and inferior epiphyseal plates. The dens of the axis (odontoid process) may be hypoplastic. Irregular ossification of the iliac crests creates a characteristic lacelike appearance on radiographs. The ilia are short and broad.

In young children, the growth plates of the proximal femurs are horizontal, with prominent spurlike projections on the medial side of the femoral necks. Ossification of the femoral epiphyses is delayed, and the long bones are short with irregular epiphyseal and metaphyseal ossification.

Differential Diagnosis. Patients with this condition bear some resemblance to persons with Morquio syndrome (see Plate 4-18). However, there is no corneal clouding and the urine contains no keratan sulfate. In fact, studies of lysosomal enzymes and histologic examination refute the hypothesis that Dyggve-Melchior-Clausen dysplasia is due to an abnormality of mucopolysaccharide metabolism.