The pathogenesis involves activated interkeukin (IL)–17–producing T cells in skin, perpetuated by an IL-23–mediated psoriasis molecular signature that reflects the pathogenic keratinocyte response.1,2,3 Ustekinumab is a US Food and Drug Administration–approved biologic agent for psoriasis that targets the IL-12/IL-23 pathways. The gene discussed is IL17A; the disease is psoriasis.