We confirmed that serum CCL20 levels markedly increased (852 pg/mL) 2 days before guselkumab therapy started, and decreased as the eruption improved after the treatment (Figure 2C). In conclusion, treatment with guselkumab was effective in this patient with PRP refractory to conventional therapies. Although further clinical studies are required, serum CCL20 levels may be a useful marker indicating PRP disease activity and providing incentive to initiate treatments targeting IL-23-Th17-pathway. [Extracted from the article]