IL17A and enthesitis: Recently, several animal model studies have demonstrated the essential role of enthesitis in pathogenesis of the SpA group of diseases [10] and shed light on the importance of specific inflammatory pathways and various cytokines in acting locally such as IL-23 [8], IL-17, and IL-22 as key pro-inflammatory cytokine in SpA potentially secreted by entheseal resident cells [8, 11].