A sporadic case of congenital hypotrichosis simplex of the scalp: difficulties in diagnosis and classification.

Hereditary hypotrichosis simplex of the scalp is a genotrichosis characterized by a hair defect limited to the scalp in the absence of other ectodermal or systemic abnormalities. Only large pedigrees consistent with autosomal dominant transmission have been described to date. In this article the clinical and scanning electron microscopy findings of a nonfamilial case of congenital scalp hypotrichosis simplex are reported. In some patients the diagnosis of sporadic hypotrichosis simplex of the scalp should be considered after ruling out all other possible causes of congenital and hereditary hypotrichosis.