Histometric assessment of psoriatic plaques treated by vitamin D3 derivatives.

BACKGROUND: Psoriasis is an immunogenetic disorder. Factor XIIIa+ dermal dendrocytes (DD) are part of the pathobiological changes in the plaque type of the disease. OBJECTIVE: The present study aimed at comparing the effect of 3 vitamin D(3) derivatives on the epidermis, microvasculature and DD in psoriasis. METHOD: Twenty men suffering from chronic plaques of psoriasis on the trunk were enrolled in this study. They applied twice a day for 3 weeks calcipotriol, tacalcitol and calcitriol, each to one plaque. Another similar lesion received petrolatum as a placebo treatment. Skin biopsies were taken at entry and at completion of the 3-week treatment phase. Immunohistochemistry was performed using the lectin of Ulex europaeus and an antibody to factor XIIIa. Computerized image analysis served to measure the stratum Malpighii area, the microvasculature area and the DD numerical density in the papillary dermis. RESULTS: At entry in the study, the 4 test sites were indistinguishable with regard to the stratum Malpighii area, the papillary microvasculature area and the papillary DD density. The 3 histometric parameters appeared correlated with each other. At completion of the 3-week treatment phase, the 3 vitamin D derivatives had decreased the size of the stratum Malpighii. In addition, calcitriol had also reduced the DD density in the papillary dermis. No other significant changes were yielded. CONCLUSION: As assessed by histometry, the psoriatic epidermis responded to a short treatment using the 3 vitamin D derivatives. The better result compared to the control site was achieved by calcitriol. DD appeared to be most controlled by the same drug. The microvasculature did not appear to be decreased at the 3-week time point in treatment.