Clinical Manifestations. At birth, the head and face are normal but oral and dental abnormalities are common, including natal teeth, multiple frenula that obliterate the buccolabial sulcus, and partial or pseudocleft in the midline of the upper lip. Precocious exfoliation and missing or peg-shaped teeth are evident later. Mesomelic and acromelic limb shortening is greater in the lower limbs and, with growth, knock-knee becomes serious enough to require surgical treatment. The hands are short and stubby with postaxial polydactyly, which also occurs in the feet in 10% of patients. The fingernails and toenails are hypoplastic or dysplastic. The trunk is not affected. Adult height varies from 42 to 60 inches. Congenital heart disease, typically an atrial septal defect, is seen in more than 50% of patients.

Radiographic Findings. The long bones show a progressive distal shortening with broadened metaphyses. In the hands, the capitate and hamate are fused or deformed. Delayed ossification of the lateral portions of the epiphyses and metaphyses of the proximal tibias results in knock-knee. The pelvis has short iliac crests and, in infancy, spurlike inferior projections from the medial and lateral margins of the acetabula. The configuration of the pelvis becomes normal by late childhood.

GREBE CHONDRODYSPLASIA

The rare Grebe chondrodysplasia is transmitted as an autosomal recessive trait. Mild shortness of the hands and feet may be an indicator of the carrier state (heterozygosity). Although stillbirth is frequent and neonatal mortality high, after infancy the prognosis for survival is good.

Clinical Manifestations. Marked shortening of both upper and lower limbs is apparent at birth. The legs are more affected than the arms, and length reduction of the long bones increases progressively from the proximal to the distal segments. The fingers are extremely short and toelike. In the short, valgus feet, the toes may be rudimentary, ball-like structures. Polydactyly occurs in 50% of patients. Adult height is only 39 to 41 inches.

Radiographic Findings. The skull and axial skeleton appear essentially normal. The limbs, however, show severe dysplasia or aplasia of all bony elements.

ACROMESOMELIC DYSPLASIA

Transmitted as an autosomal recessive trait, acromesomelic dysplasia results in severely restricted growth.

Clinical Manifestations. This short-limb form of dwarfism is usually apparent in the first few weeks or months of life. Head size is normal, but the frontal bones may be prominent and the midface mildly hypoplastic and flattened. Limb shortening is greatest in the middle or distal segments. Range of motion of the elbow joints is limited by partial dislocation of the radial heads. The forearms are often bowed. Fingers, toes, and nails are very short. The thorax is small with mild anterior flaring of the lower ribs. Exaggerated lumbar lordosis makes the buttocks prominent; lower thoracic kyphosis is also common. Adult height ranges from 38 to 48 inches.

Radiographic Findings. Radiographs reveal a progressive shortening of the long bones, bowing of the radii, and often subluxation of the radial head. The epiphyses are relatively normal in infancy and become cone shaped later. The hands are unusually squat, and the phalanges appear square or sugarloaf shaped. The height of the vertebral bodies is minimally reduced, primarily in the posterior portions.