Alopecia areata update Part I. Clinical picture, histopathology, and pathogenesis

Alopecia areata (AA) is an autoimmune disease that presents as nonscarring hair loss, although the exact pathogenesis of the disease remains to I)e clarified. Disease prevalence rates from 0.1% to 0.2% have been estimated for the United States. A-A can affect an, hair-hearing area. It often presents as well demarcated patches of nonscarring alopecia on skin of overtly normal appearance. Recently, newer clinical variants have been described. The presence of AA is associated with a higher frequency of other autoimmune diseases. Controversially, there may also be increased psychiatric morbidity in patients with AA. Although some AA features are known pool-prognostic signs, the course Of the disease is unpredictable and the response to treatment can be variable. Part one of this two-part series on AA describes the clinical presentation and the associated histopathologic picture. it also proposes a hypothesis for AA development based on the most recent knowledge of disease pathogenesis. (J Am Acad Dermatol 2010;62:177-88.)