Pseudo Achondroplasia

A recognized form of short-limb dwarfism, body proportions similar to those of Achondroplasia except a normal sized head and normal facial features.

Clinically characterised by normal head size and facial features (Cf Achondroplasia), disproportionately long trunk, rhizomelic shortening of extremities, short stubby fingers. Incomplete elbow extension. Delayed development of the femoral head, resulting in hip dysplasia and a waddling gait. Genu varus deformity of knee. Severe ligamentous laxity (with exception of elbow)

The radiographic features:

in spine platyspondyly, flame-shaped vertebrae with anterior projections. The interpedicular distance does not progressively decrease in the lumbar spine ( Cf. Achondroplasia). Exaggerated  thoracolumbar kyphosis, mild to moderate scoliosis. At CV junction odontoid hypoplasia.

Long bones are short and broad. Both the epiphyses and metaphyses are affected. Flaring of the metaphyses. angulations. Delayed epiphyseal ossification. Epiphyses appear irregular and fragmented.

In joints hips and knees are primarily affected. In hip, shallow acetabulum with hip dysplasia and secondary degenerative changes. Marked dysplasia of the femoral head, short neck of femur. Flattend femoral head may show fragmention. In knee Genu varum deformity.

Short stubby metacarpals.

Normal skull radiograph.

Condition will not become apparent until between 18 and 24 months of age. Manifests itself over time. Ultimately, adult stature is between 82 and 130 cm.