Clinical and histologic findings in temporal triangular alopecia.

Abstract

Temporal triangular alopecia (TTA; also called "congenital triangular alopecia") is a common disorder that is assumed to be congenital. Little is known about its histologic features. Our purpose was to describe four new cases, review the literature, and present histologic features based on vertical and transverse sectioning. The history, clinical features, and histologic findings of four patients with TTA are described and the relevant literature reviewed. Lesions of TTA are seldom congenital, and most are best described as lancet-shaped. The "bald spot" contains normal numbers of hairs, although virtually all are vellus or indeterminate follicles. Most cases of TTA appear to develop during the first few years of life, and the designation "congenital" is a misnomer. The appearance of alopecia can be best explained as a focal zone of hair miniaturization leading to vellus hair formation.