Both AD and psoriasis are characterized by a defective skin barrier, dysregulated immune responses (i.e., type 2 immunity or interleukin [IL]-4/IL-13 axis inflammation in AD and type 3 immunity or IL-23/IL-17 axis inflammation in psoriasis), genetic predispositions, and causative environmental factors [6,7]. The gene discussed is IL17A; the disease is Alzheimer disease.