IL-22 belongs to the IL-10 family, which also includes IL-10, IL-19, IL-20, IL-24 and IL-26.137 Prior studies have found that the level of IL-22 is significantly increased in the serum and lesions of patients with psoriasis.138,139 The concentration of serum IL-22 is also significantly correlated with the PASI score and is regarded as an indicator of therapeutic effect, as treatment with etanercept or methotrexate can reduce the level of serum IL-22. This evidence concerns the gene IL10 and psoriasis.