EPIDERMAL DIFFERENTIATION CHARACTERISTICS OF THE PSORIATIC PLAQUE DURING SHORT-CONTACT TREATMENT WITH DITHRANOL CREAM

Dithranol has been used successfully in the treatment of psoriasis for more than 75 years, and much in vitro and in vivo research has been d one on the elucidation of the mode of action of this potent and safe a ntipsoriatic therapy. In vivo research has revealed major effects of d ithranol on epidermal proliferation and inflammation. Information on t he in vivo effects on epidermal differentiation is limited. Therefore, the dynamics of a set of differentiation markers (keratin 16, filaggr in, keratinocyte transglutaminase, involucrin) and markers for prolife ration and inflammation (Ki-67, T lymphocytes, polymorphonuclear leuco cytes) were studied in skin biopsies of six patients with psoriasis du ring 4 weeks of dithranol therapy The treatment regimen involved a sho rt contact protocol at our out-patient day treatment centre with an ea sily washed off cream. Treatment resulted in a decrease of the PASI sc ore of 48% in 4 weeks. Immunohistochemically, a major decrease of kera tin 16 content and virtually complete restoration of the filaggrin pos itive cell layer were seen. These changes proved to be significant by comparison of the markers over the group of six patients. Although man y other topical treatments for psoriasis (occlusive therapy and vitami n D-3 analogues) result in a prominent reduction in the amount of tran sglutaminase and involucrin positive cell layers, the effect of dithra nol on these markers is minimal.