MPO and psoriasis 14, pustular: The interleukin-36 (IL-36) pathway plays a critical role in GPP [42,43], as evidenced by loss-of-function mutations in the IL36RN gene and related genes such as CARD14, AP1S3, SERPINA3, and MPO, and the overexpression of IL-36 cytokines in GPP lesions [44,45,46,47] (Figure 1).