Evaluation of time-dependent response to psoralen plus UVA (PUVA) treatment with topical 8-methoxypsoralen (8-MOP) gel in palmoplantar dermatoses

Background Topical psoralen plus UVA (PUVA) is an effective treatment for localized forms of eczema, psoriasis, and palmoplantar pustulosis, which avoids some of the undesirable side-effects of systemic psoralens. Aims In this study, the efficacy of topical PUVA treatment with 8-methoxypsoralen (8-MOP) gel was compared with placebo plus UVA in chronic recurrent palmoplantar dermatoses. Methods Twenty-two patients with palmoplantar disease (11 with psoriasis vulgaris, six with eczema, and five with pustulosis) were enrolled in the study. The study design was a left-right comparison: one hand or foot was treated with 8-MOP 0.01% gel plus UVA, whilst the contralateral hand or foot received placebo and UVA for 6 weeks. Twenty minutes after application of the gel, both sides were exposed to UVA. The treatment regimen was three times a week, and the UVA dose was increased weekly by 20%. Results A comparison of the pre- and post-treatment scores with regard to the severity of the clinical picture and the infiltration of plaques showed a significant decrease (from 7.5 +/- 2.0 to 2.5 +/- 2.1 and from 2.0 +/- 0.7 to 0.3 +/- 0.5, respectively) in the sites treated with 8-MOP gel compared with placebo after 6 weeks. Conclusion The results of the study indicate that at least 18 courses of local PUVA within 6 weeks, with a cumulative dose of 87 J/cm(2), are required to induce a significant decrease in the disease severity and an improvement in the infiltration of plaques due to 8-MOP gel at a concentration of 0.01% when treating chronic recurrent palmoplantar dermatoses.