Similar to other autoimmune diseases, AA is associated with particular major histocompatibility complex class II haplotypes that confer an increased risk, including DQB1*03, DRB1*1104, DRB1*0401, and DQB1*0301. The overlap in the DQB1 regions in narcolepsy and AA suggests a concordance in patients with AA and narcolepsy that may link the 2 presumed autoimmune diseases in susceptible patients. In addition, CD200, which is expressed predominantly in outer root sheath follicular keratinocytes and may prevent undesired activation of autoreactive T cells,5 was originally designated orexin 2. Orexins 1 and 2 are G protein–coupled receptors to which orexins A and B bind. The data from the 2 cases reported herein and the 3 taken from the literature1 (Table) suggest, but do not prove, that there may be more than a random association of AA and narcolepsy occurring in some patients.