How the Diagnosis is Made

Considering that the skeletal deformities of hypochondroplasia are moderately similar to those of achondroplasia, radiographic findings must be well-scrutinized to give a correct diagnosis. The best features to examine are the skull and pelvis; each are more severely affected in the case of achondroplasia. In order to differentiate between hypochondroplasia and familial short stature, vertebral and pelvic changes should be considered. Vertebral abnormalities are characteristic only of hypochondroplasia. The appearance of the long bones may be similar to metaphyseal chondrodysplasia, Schmid type. Again, the differential feature is the vertebral abnormalities, which are only present in hypochondroplastic patients. It is difficult to diagnosis hypochondroplasia in infancy, although birth length may be slightly below average. By 3 years of age, slow growth and bowlegs are early indicators of this skeletal dysplasia.