A punch biopsy specimen from the left side of the scalp showed follicular miniaturization with an absence of hair follicles in anagen phase. The overlying epidermis was atrophic, and there was subcutaneous fat atrophy consistent with previous steroid use. No inflammation was noted within the dermis or subcutaneous tissue.
Congenital triangular alopecia was first described by Sabouraud1 in 1905. We found 55 cases reported in the literature.2- 4 Although it is considered to be rare, this entity is probably more common than is generally thought. In one series of 6200 randomly selected patients, 7 patients (0.11%) with congenital triangular alopecia were found.3 Another group of investigators diagnosed 4 cases in a 1-year period.4 Some investigators suggest that this condition is underreported because it is often overlooked.5,6 Also, because the alopecia is asymptomatic and remains stable throughout life, it is likely that many patients never consult a physician.6
Recalcitrant Patch of Alopecia on the Scalp. Arch Dermatol. 2000;136(2):259-264. doi: