Recessive metaphyseal dysplasia without hypotrichosis. A syndrome clinically distinct from McKusick cartilage-hair hypoplasia.

Among children with recessive metaphyseal dysplasia involving the knees and extremities, two types can be distinguished. In true cartilage-hair hypoplasia, as described by McKusick, many patients show clinical hair involvement and variable immunodeficiency. We present a series of six patients with the same radiological changes, but without apparent hypotrichosis. We suggest that they should be considered as having a variant form of cartilage-hair hypoplasia, with a clinically distinct phenotype, which could be as common as 'true' cartilage-hair hypoplasia among non-Amish populations. Microscopic examination of the hair may show reduction in the diameter of the hair shaft. This form of metaphyseal dysplasia may result from allelic heterogeneity.