Although it is known that psoriasis and PsA patients have increased frequencies of IL-17A+ and IL-22+ CD4+ T cells in their peripheral blood and synovial fluid [3, 12], it is not clear if CCR6+ memory Th cells differ between psoriasis and PsA patients and if one or multiple subpopulations play a role in the transition of psoriasis to PsA. This evidence concerns the gene IL17A and psoriasis.