Congenital Triangular Alopecia - Report of a Case and Review of the Literature

We report a 3-year-old Chinese girl who presented with an 18-month history of a localized asymptomatic triangular area of hair loss in the right frontotemporal area. There was no history of trauma. The parents were non consanguinous and there was no family history of a similar lesion. Her 42-year-old father had androgenic alopecia that was first noted 3 years ago. Physical examination revealed a patch of alopecia 3.5 x 4 cm over the right frontotemporal area, with its apex towards the vertex. The overlying skin was otherwise normal. In particular, there was no scaling, scarring, erythema, or induration in the alopecic area. Dermoscopy showed normal follicular openings with thin vellus hairs over the affected area and terminal hairs in the adjacent scalp. Based on the characteristic history and physical findings, a diagnosis of congenital triangular alopecia was made. Awareness of this condition is important so that it will not be overlooked or misdiagnosed.