A Randomized Clinical Trial: The Comparative Therapeutic Efficacy of Tap Water‐ UVA , Saltwater‐ UVA , and Conventional Bath PUVA in Palmoplantar Pustulosis

Background & Purpose Bath or oral PUVA is a key treatment modality for palmoplantar pustulosis (PPP), whereas topical PUVA and UVB have proven ineffective. Immersion in water prior to UVA may represent a therapeutic option. Method This study was a prospective, open label, three‐arm parallel‐group randomized controlled trial conducted from 2014 to 2017. The study was conducted in Ankara University Medical School Department of Dermatology and Venereology. The ethical committee approval was granted (07.10.2013‐ no 15‐585‐13) and the trial registration number was NCT06458868. All participants had a biopsy with a confirmed diagnosis of PPP. The primary endpoint of the study was defined as having achieved a PPASI50 response at week 36. Out of 114 eligible patients, 68 patients were enrolled in the study. Randomization was performed using a computer program (clinstat). All arms received UVA irradiation for 36 sessions starting at 0.25 J/cm 2 with incremental increases. Bath PUVA arm: Local baths with water containing 0.5 mg methoxypsoralen per litre at 37°C for 20 min prior to phototherapy. Tap Water (TW) Group received local baths in tap water, Saltwater (SW) Group received local baths in 25% w/v saline solution, both at 37°C for 20 min prior to phototherapy. Results Out of 68 enrolled participants, 50 completed the study (F/M: 43/7, age: 47.8 ± 10.3 years). In the intention to treat set, PPASI‐50 response rates were 38.5%, 57.1%, and 71.4% in the TW, SW, and bath‐PUVA groups ( p = 0.085). In the per protocol set, corresponding rates were 52.6%, 85.7%, and 88.2% ( p = 0.031). Conclusions Immersion in water or saltwater prior to UVA without psoralens may provide a therapeutic effect.