Alopecia areata (AA) is a nonscarring hair loss disorder with a 2% lifetime risk. Most patients are below 30 years old. Clinical types include patchy AA, AA reticularis, diffuse AA, AA ophiasis, AA sisiapho, and perinevoid AA. Besides scalp and body hair, the eyebrows, eyelashes, and nails can be affected. The disorder may be circumscribed, total (scalp hair loss), and universal (loss of all hairs). Atopy, autoimmune thyroid disease, and vitiligo are more commonly associated. The course of the disease is unpredictable. However, early, long-lasting, and severe cases have a less favorable prognosis. The clinical diagnosis is made by the aspect of hairless patches with a normal skin and preserved follicular ostia. Exclamations mark hairs and a positive pull test signal activity. Dermoscopy may reveal yellow dots. White hairs may be spared; initial regrowth may also be nonpigmented. The differential diagnosis includes trichotillomania, scarring alopecia, and other nonscarring hair loss disorders such as tinea capitis and syphilis.
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