JAMA Dermatology - Alopec...

Alopecia Areata (AA) is a type of hair loss disorder caused by the immune system.

It most often appears as patchy areas of hair loss on the scalp but can occur anywhere on the body. AA can affect people of any age, race, or sex. While not a dangerous condition, it can substantially affect patients’ lives.

Hair loss in AA can be unpredictable. Most patients with AA will have a single patch that fully resolves on its own over the course of several months. Others may have more frequent episodes with more areas of hair loss. Around 5% to 10% of people with AA develop the totalis (complete loss of hair on the entire scalp) or universalis (complete loss of hair on the whole body) subtypes, and these cases are more difficult to treat.