Efficacy of excimer light therapy (308 nm) for palmoplantar pustulosis with the induction of circulating regulatory T cells.

In this open-label study, we investigated the efficacy of excimer light (308 nm) with a filter to cut off wavelengths below 297 nm for the treatment of palmoplantar pustulosis (PPP). Twenty patients with PPP were recruited and treated once a week for a total of 30 sessions. Patient response was assessed every 10 sessions based on the Palmoplantar Pustulosis Area and Severity Index (PPPASI) score. Levels of Th17 cells and regulatory T cells (Treg) in the peripheral blood in patients with PPP were also evaluated. Mean PPPASI score was 19.5 at baseline, 13.2 at 10 treatments, 10.9 at 20 treatments and 9.5 at 30 treatments. Th17 levels after excimer therapy were not significantly different from those at baseline. In contrast, Treg levels after excimer therapy were significantly higher than those at baseline.