Temporal Triangular Alopecia

Temporal triangular alopecia (TTA), also known as congenital triangular alopecia, is a condition that may be present at birth or noticed during the first decade of life, with uncertainty about whether it can develop after birth. It is characterized by lancet-shaped, hairless patches in the temporal region, which may be unilateral or bilateral, and persist for life. The condition has been associated with various congenital disorders and may be inherited as a paradominant trait. Histologically, TTA shows a normal or nearly normal total number of hair follicles, but almost all are vellus hairs with no significant inflammation or other abnormalities, and no fibrous "streamers" (stelae) as seen in androgenetic alopecia. Treatment is not usually required, but options include topical minoxidil, hair transplantation, or excision for cosmetic improvement. Diagnosis requires careful examination, as vertical sections alone are insufficient, and TTA can be mistaken for androgenetic alopecia if only upper dermal levels of horizontal sections are examined.