Marked variability in the radiographic features of cartilage-hair hypoplasia: case report and review of the literature.

Cartilage-hair hypoplasia (CHH) is a rare recessive metaphyseal chondrodysplasia characterized by severe short stature, ectodermal dysplasia, anemia in childhood, immune deficiency, susceptibility to malignancy, and normal intelligence. Short, thick long bones, metaphyseal flaring and irregularities, and globular epiphyses at the knees and ankles are the typical radiographic findings. The diagnosis is primarily made on the basis of clinical features, although mutations in the RMRP gene have recently been described in affected individuals, facilitating confirmation of the clinical diagnosis in atypical patients. We present a patient with two RMRP mutations whose stature and ectodermal features supported the diagnosis of CHH, but whose radiographic findings and other extraskeletal findings did not. We propose that the most consistent and reliable features of CHH are short stature of prenatal onset and ectodermal dysplasia, and suggest that the diagnosis of CHH be considered and mutation analysis pursued even when typical radiographic findings are absent.