308-nm excimer light is effective for palmoplantar pustulosis regardless of the presence or absence of focal infection: Single-center real-world experience of treatment for palmoplantar pustulosis

Palmoplantar pustulosis (PPP) is relatively rare and recognition of PPP is different in different countries. Therefore, real-world data are limited. Local phototherapy for the palms and the soles is commonly used to treat PPP due to tolerable safety. However, data on the effectiveness of 308-nm excimer light are limited. In our study, we retrospectively investigated the effectiveness of treatments for PPP, especially phototherapy (308-nm excimer light), in our department. In addition, we examined whether smoking status and focal infection affected responsiveness to treatment of PPP. Patients who were diagnosed with PPP by board-certified dermatologists and visited our hospital from April 2015 to August 2018 were analyzed in this study. We collected data on PPP area severity index (PPPASI) before treatment. We also collected data on PPPASI in May to August 2018 as "after treatment" from all patients. Patients who received any treatment for less than 3 months were excluded. Nineteen patients (16 women and three men) were analyzed in this study. In patients treated with phototherapy (n = 12), PPPASI significantly decreased from a mean +/- SD of 16.5 +/- 10.3 to 4.5 +/- 3.6 (p = 0.004), whereas it did not in patients treated without phototherapy (n = 7). Patients who quit smoking showed a significant decrease in PPPASI after treatment (16.8 +/- 12.7 to 2.4 +/- 2.9, p = 0.008). Regarding focal infection, in patients treated without phototherapy, the reduction rate of PPPASI was significantly lower in patients with focal infection than in those without focal infection (17.7 +/- 21.5%, 71.1 +/- 19.3%, p = 0.035), indicating that focal infection is associated with intractability. Meanwhile, in patients treated with phototherapy, PPPASI decreased regardless of the presence or absence of focal infection. In conclusion, our study demonstrated the effectiveness of local phototherapy consisting of 308-nm excimer light, regardless of focal infection. Patients who quit smoking were responsive to any treatment, indicating the importance of smoking cessation.