β‐Defensin 2 is an antimicrobial peptide produced by epithelial cells including keratinocytes, the production of which is inducible by injury, infection or cytokines.19 In active psoriatic lesions, higher BD‐2 expression has been reported compared with the levels in atopic dermatitis and healthy skin.20 In the current study, there was a strong correlation between serum BD‐2 level and psoriatic disease activity, and the change in BD‐2 preceded the improvement in PASI score, suggesting that the suppression level of BD‐2 can predict the response to therapy. The gene discussed is DEFB4A; the disease is infection.