Alopecia areata (Alopecia areata (AA))

Alopecia areata (AA) is autoimmune hair loss. The immune system targets actively growing follicles, producing sharply-bordered, smooth round or oval patches of complete hair loss. The scalp inside the patch is normal, not scarred.

Course is unpredictable. Roughly half of patchy AA cases regrow spontaneously within 12 months without treatment. A subset progresses to alopecia totalis (complete scalp hair loss) or alopecia universalis (loss of all body hair).

The diagnostic feature on trichoscopy is “exclamation mark” hairs at the patch border: short, broken hairs that taper toward the scalp.

The treatment landscape changed substantially in 2022 to 2024. Three oral JAK inhibitors are now FDA-approved for severe AA: baricitinib, ritlecitinib, deuruxolitinib. Roughly a third of patients with severe AA achieve significant scalp hair regrowth on these drugs. Stopping leads to relapse in most. Topical or intralesional corticosteroids remain options for limited disease.