THE EFFECT OF FUMARIC-ACID ESTERS AND DITHRANOL ON ACANTHOSIS AND HYPERPROLIFERATION IN PSORIASIS-VULGARIS

In this study we investigated the histological changes, regression of acanthosis and rate of proliferation, that accompany the healing of ps oriatic lesions after fumaric acid esters and dithranol treatment, Bio psies were taken before and during therapy as well as from neighbourin g untreated, clinically uninvolved skin and healthy, non-psoriatic vol unteers, Specimens were assessed using computer-supported image analys is and immunohistology. The parameters primarily examined were the hei ght of the rete pegs and of the epithelium above the papillary body, t he rate of proliferation, the actual number of cells in the two epider mal compartments and the cellular density in the epidermis, Both fumar ic acid esters and dithranol reduce the degree of acanthosis; however, the mechanism and the rate of the reduction differ, While under fumar ic acid esters the reduction is more rapid at first but subsequently s lows down, dithranol leads to a slow but steady decrease of epidermal thickness, so that at the end of our study the degree of acanthosis wa s less under dithranol. As an underlying mechanism of action, we found that fumaric acid esters reduce the rate of proliferation and thereby decrease the number of cells per rete peg as well as the size of the individual keratinocytes. Dithranol in contrast does not reduce cell r enewal, The decrease of the number of cells in the rete pegs might be caused by an increased differentiation time.