Suppression of palmoplantar pustulosis symptoms with oral 8-methoxypsoralen and high-intensity UVA irradiation.

9 patients with long-standing palmoplantar pustulosis were treated with oral 8-methoxypsoralen and high-intensity UVA irradiation (PUVA, 46.2 mW/cm2). 20 irradiations with single doses of up to 14.8 J/cm2 resulted in good or excellent clearing in 4 out of 5 patients, while none of 4 patients receiving 5-6 irradiations of up to 5.2 J/cm2 improved significantly. Comparison with earlier investigations leads to the conclusion that systemic PUVA is more efficient than topical PUVA in the treatment of palmoplantar pustulosis. This may result from different skin distribution of psoralen or from a more rapid decline in the photosensitivity of topically medicated skin during prolonged irradiation as compared to skin sensitized by oral psoralen administration. The use of a high-irradiance UVA source diminishes the influence of this time factor and improves patient compliance.