Pressure-Induced Alopecia: Presence of Thin Hairs as a Trichoscopic Clue for the Diagnosis.

Pressure-induced alopecia (PA) is an unusual pattern of circumscribed hair loss that occurs after ischemic changes on the scalp. Trichoscopic findings described in the literature are scarce, nonspecific, and include black dots, broken hairs, circle hairs, and erythema. However, we report 3 cases of PA in which trichoscopy also showed many vellus and thin hairs. Possibly, the maintenance of these hair shafts may be explained by the more superficial insertion of their bulbs on the skin and/or their lower metabolic rates, making them suffer less from local hypoxia. Therefore, the authors suggest that these relevant signs should be added as a clue for the diagnosis of PA in doubtful cases.