Minimal Phototoxic Dose for a Vitiliginous Skin Lesion

Park, Jang Kyu; Kim, Youn Soo; Rho, Young Woo; Yoon, So Yeong; Kim, Tae Won; Lee, Woong Jae; Suhr, Ki Beom; Lee, Jeung Hoon

Abstract

BACKGROUND: It is mandatory to measure the minimal phototoxic dose(MPD) in order to determine adequate irradiation of UV-A in photochemotherapy. However, the measurement of MPD is not easy in some cases due to inadequte size and site of lesions, time and manpower.
OBJECTIVE
The purspose of this study was to standardize the minimal phototoxic dose for a vitiliginous lesion.
METHODS
The minimal phototoxic dose of UV-A was measured in 82 vitiligo patients. Then we analyzed the MPD according to the sex, age, site of the vitiliginous lesions, duration of disease, and administration route of the photosensitizer.
RESULTS
1. There were no significant differences between exposed and unexposed areas in MPD in both cases of topical and systemic administration of the photosensitiser. 2. There was no significant correlation between disease duration and MPD in both cases of topical and systemic administration of the photosensitiser. 3. In the group of topical application of 8-methoxypsoralen cream, MPD for males and females were 0.53+0.38J/cm2 and 0.48+0.32J/cm2 respectively without significant difference in sex. 4. In the group of systemic administration of 8-methoxypsoralen, there was a significant difference between males and females in MPD. The MPD in males and females were 1.38+0.72J/cm2 and 2.51 + 1.40J/cm2, respectively. 5. In the group of topical application of 8-methoxypsoralen cream, the MPD in 2nd decade patients was the highest(0.80+0.55J/cm2). The MPD had a tendency to decrease gradually as age receded from the 2nd decade. 6. In the group of systemic administration of 8-methoxypsoralen, there was a tendency for the MPD to be increased according to age without statistical significance. 7. MPD in the group systemically administrated with 8-methoxypsoaralen was four-fold to that of the topical application group.
CONCLUSION
It may be valuable to keep in mind that there was a statistical differrence in MPD between sexes in systemic administration of the photosensitizer, and that MPD was different according to patients age in the topical application group.