Interleukin-23 (IL-23), a cytokine involved in both innate and adaptive immunity that activates T helper (Th17) lymphocytes, stimulating the production of interleukin 17 (IL-17), is strongly implicated in localized inflammation at tendon–bone insertion sites, playing a key role in enthesitis [8,9]. The gene discussed is IL17A; the disease is enthesitis.