PSTPIP1 and pyogenic arthritis-pyoderma gangrenosum-acne syndrome: PAPA syndrome is a rare autosomal dominant disorder caused by gene mutations of proline/serine/threonine phosphatase-interaction protein 1 (PSTPIP1/CD2BP1), resulting in the aberrant activation of innate immune systems followed by excessive overproduction of proinflammatory cytokines such as IL-1β, TNF-α, IL-6, IL-17A, and IFN-γ [72].