Psoriasis is largely driven by T helper (TH) 1 (TH1) and TH17 cells with the involvement of IL-17A, TNF-α and IL-22, whereas AD is associated with infiltration of TH2 cells in particular (Guttman-Yassky and Krueger, 2017; Nestle et al., 2009). Here, IL17A is linked to Alzheimer disease.