Large increments in psoralen-ultraviolet A (PUVA) therapy are unsuitable for fair-skinned individuals with psoriasis

The ideal psoralen-ultraviolet A (PUVA) regimen for chronic plaque psoriasi s has yet to be established. There are four components to a PUVA regimen: t he dose of psoralen, the starting dose of UVA, the frequency of treatment a nd the incremental UVA dose protocol. Recent studies have been directed at trying to optimize the efficacy of PUVA while minimizing acute side-effects and the risk of cutaneous carcinogenesis, believed to be independently rel ated to the cumulative dose of UVA and the total number of treatments, The British Photodermatology Group recommends two twice-weekly PUVA regimens: o ne starts with 50% of the minimal phototoxic dose (MPD) and uses weekly inc rements of 40%, 30%, 25%, 20%, 15%, 10% and 5% of the previous dose to a ma ximum of 14.5 J/cm(2); the other starts with a fixed dose based on skin typ e and uses weekly dose increments of 40%, decreasing to 20% once erythema d evelops, We undertook a prospective randomized controlled trial comparing t hese regimens in 85 Irish patients. The clearance rate with the MPD regimen was lower than with the skin type regimen, 67.5% vs. 95% (P < 0.05). The r easons for treatment failure were grade 3 erythema and severe PUVA itch. Th ere was a trend suggesting that patients with skin types I and II, but not skin type III, required a higher cumulative UVA dose and fewer exposures to clear with the MPD regimen than the skin type regimen, although this did n ot reach statistical significance, Grades 2 or 3 erythema were very common in both treatment groups (52.5% of the skin type group and 45% of the MPD g roup), This is the third study to suggest that patients with skin types I a nd II receive a higher total UVA dose when the starting dose is 50-70% of t he MPD (rather than 0.5 J/cm(2) for skin type I and 1.0 J/cm(2) for skin ty pe II) and when large dose increments are used. We suggest that smaller dos e increments should be used in patients with skin types I and II.