IL-17F shares a gene locus with, is coexpressed with, and has a similar protein structure and biologic activity as IL-17A; IL-17F is elevated in the sera and lesional skin (LS) of patients with psoriasis (Blauvelt and Chiricozzi, 2018; Elloso et al, 2012; Johansen et al, 2009; Reich et al, 2021; Soderstrom et al, 2017). The gene discussed is IL17A; the disease is psoriasis.