Epidemiology

AA is a common disorder with an estimated prevalence of 1 in 1000 people and a worldwide lifetime incidence of around 2%, which is similar to that reported in the US population.[2][4][5] It affects both sexes equally and is seen in all age groups with no known ethnic predominance. Incidence is higher in children and young adults.[6]

Patients usually present with several episodes of hair loss and hair regrowth during their lifetime. The course is irregular and unpredictable. The recovery from hair loss may be complete, partial, or none. The incidence of the severe chronic form of the condition is 7% to 10% in affected people.[7] Indicators of a poor prognosis are the presence of other immune diseases, family history, young age at onset, nail dystrophy, extensive hair loss, and ophiasis (hair loss at the inferior hair line of the scalp [i.e., inferior-parietal/occipital scalp]).[2][8] Atopy may be an indicator of poor prognosis, but recent evidence is lacking.[2]

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