IL23A and psoriasis: Dear Editor, More than 60 genomic loci have been described at which variation modulates susceptibility to plaque-type psoriasis in European populations.1 The primary risk allele is HLA-C*06:02 which may be involved in the presentation of autoantigens.2,3 Some therapies for psoriasis specifically target mediators such as interleukin (IL)-12 and/or IL-23, which exert possible educational functions during antigen presentation, and genetic factors associated with psoriasis may also be useful in the identification of responders to anticytokine therapies.