ERYTHEMAL AND THERAPEUTIC RESPONSE OF PSORIASIS TO PUVA USING HIGH-DOSE UVA

In PUVA treatment of psoriasis, clinical observation suggests that uni nvolved skin is more susceptible to PUVA erythema than lesions of psor iasis. If this is the case, then the efficacy of PUVA treatment might be increased by using localized high-dose WA restricted to lesional sk in. We have therefore studied the erythemal and therapeutic response o f psoriasis to PUVA using high-dose UVA and, for comparison, the eryth emal response to UVB. In 14 patients, an area of psoriasis and adjacen t uninvolved skin were exposed to a series of UVA doses (350 +/- 30 nm , 1-16J/cm(2)), using an irradiation monochromator. Six other patients were similarly phototested with a series of UVB doses (300 +/- 5 nm, 20-112 mJ/cm(2)) to both uninvolved and lesional skin. Erythema was ju dged visually at 72 h for psoralen-UVA, and at 24 h for UVB, and measu red using a scanning laser-Doppler velocimeter. In 10 patients, PUVA t herapy using high-dose UVA was subsequently given to lesional skin (8- 16J/cm(2) twice weekly) in addition to conventional whole-body PUVA. F or psoralen-UVA, the minimal phototoxic dose within psoriasis was incr eased by a factor of 4 compared with non-lesional skin (P < 0.01, Wilc oxon signed-rank test). For UVB the minimal erythema dose within psori asis was higher than that for non-lesional skin (medians > 112 and 28 respectively, P < 0.05). Laser-Doppler measurements confirmed that the reduced erythemal sensitivity was not due to masking of response by p re-existing increased blood nux within psoriasis. In six patients, the sites subsequently treated twice weekly with PUVA, using high-dose WA , cleared faster (median number of treatments 3), but with a similar c umulative UVA dose, compared with adjacent lesional skin treated with conventional PUVA (median number of treatments 12). This study demonst rates that psoriasis may clear rapidly, without burning, using high-do se UVA. Availability of a suitable irradiation apparatus would allow r apid and effective PUVA treatment to be used for localized, resistant disease.