Pressure alopecias: A review

Pressure-induced alopecias (PA) are an infrequent group of scarring and non-scarring alopecias that occur after ischemic obstruction of capillaries that leads to circumscribed areas of hair loss. Initially described after prolonged surgeries or immobilization, Type 1 PA occurs after sustained external pressure to the skin, mainly the scalp prominences. Alopecia induced by cosmetic procedures, referred in this review as Type 2 PA, is reported with increased frequency in literature and predominantly emerges from pressure exerted by the volume of injectables. It is important to differentiate Type 2 PA from vascular occlusion-induced alopecia, as they represent distinct entities. Clinically, PA may present with erythema, swelling, and tenderness; however, alopecia might be the sole manifestation. Crusts and ulceration are associated with a worse outcome and a higher risk for scarring alopecia. Prompt diagnosis is paramount to prevent complications. Trichoscopy, although considered non-specific, may provide relevant clues for an accurate diagnosis. Hair regrows in most cases, but prognosis depends on ischemia severity and timely treatment with reperfusion therapies or mobilization. Treatment for hair loss is usually not necessary, as the disease in most cases is self-limited and reversible. The role of topical minoxidil and corticosteroids remains unknown.