title: Alopecia areata--Part I: Background .
abstract: Alopecia areata is a trichosis characterized by loss of hair, with the abrupt onset of round or oval, nonscarring, flat, single or multiple areas of alopecia lesions, which can coalesce. Several hypotheses have been raised to explain its etiology, with autoimmunity being accepted until today, along with genetic factors.
authors.forename: Juliany
authors.initials: J
authors.lastname: Estefan
authors.forename: Marcia
authors.initials: M
authors.lastname: Ribeiro
authors.forename: Eliane
authors.initials: E
authors.lastname: Abad
authors.forename: Simone
authors.initials: S
authors.lastname: Saintive
authors.forename: Marcia
authors.initials: M
authors.lastname: Ramos-e-Silva
mesh_terms: D000506:Alopecia Areata / Q000209:etiology / Q000276:immunology / Q000473:pathology*; D015551:Autoimmunity; D020022:Genetic Predisposition to Disease; D006801:Humans