Clinical Manifestations. The moderately short stature of the short-limb type is evident by 18 to 24 months of age. The head and face are not affected. The wrists are prominent or enlarged, and often the fingers do not extend fully. Bowleg, commonly the first sign, becomes obvious shortly after the child begins to walk; if severe, the bowing produces a waddling gait and contributes to the height reduction. Poor alignment of the lower limbs can lead to symptomatic osteoarthritis in the hips and knees. Flaring of the lower rib cage signals trunk involvement, and the general habitus is stocky or chubby. Adult height is 51 to 63 inches.
Radiographic Findings. Metaphyseal abnormalities vary from mild scalloping to gross irregularities in the ankles, knees, wrists, shoulders, and hips. Although metaphyseal lesions appear to heal with bed rest, they recur once weight bearing is resumed. The epiphyseal lines are wide, and epiphyseal ossification centers appear normal.
Coxa vara and bowleg are common, and the long bones and femoral necks are short. The acetabular portions of the ilia tend to be broad, and the acetabular roof, which is normally vertical, is horizontal. Long bones in the hand and foot are mildly to moderately shortened, but metaphyseal changes are minor or absent.
Differential Diagnosis. This type of metaphyseal chondrodysplasia has frequently been confused with vitamin D–resistant rickets. Clinical and radiographic findings are quite similar. However, vitamin D–resistant rickets has an X-linked dominant inheritance, whereas the Schmid-type metaphyseal chondrodysplasia is transmitted as an autosomal dominant trait. Unlike vitamin D–resistant rickets, there are no characteristic biochemical changes (serum calcium, phosphate, and alkaline phosphatase levels are normal) and no beneficial response to administration of vitamin D.
< div class='tao-gold-member'>