A clinical and flow cytometric model to study remission and relapse in psoriasis

The aim of the present study has been to analyse remission and relapse characteristics in psoriasis vulgaris. In 15 patients, two different psoriatic lesions (clinical and flow cytometric study) were treated with clobetasol propionate until clearance for maximally 23 days. In the clinical study only cleared lesions were divided into three test sectors with different post-clearance treatment: (1) alcoholic solution under occlusion, (2) occlusion only, and (3) no treatment. In the flow cytometric study, biopsies were taken from the test lesion before clobetasol therapy (i), at clearance (ii), and at relapse from both visibly affected and unaffected skin (iii, iv). Epidermal proliferation, differentiation and inflammation were quantified by multiparameter flow cytometry. The clinical evaluation worked well and could discriminate between the different therapy modalities. After 28 days, 80% of untreated sectors showed a relapse. Occlusion decreased this percentage to 50%. Application of the alcoholic solution further decreased this percentage to 30%. The flow cytometric analysis demonstrated a very low proliferative activity of the basal compartment at clearance. This activity was higher in the visibly unaffected skin at relapse, whereas highest values were assessed in the affected skin at relapse. Interestingly, at relapse the proliferative activity in the suprabasal compartment of the visibly unaffected skin had increased to values identical to the affected skin. The present model allows standardized comparison of different approaches for maintenance therapy in psoriasis vulgaris. We demonstrate that occlusion has an inhibitory effect on the tendency to relapse after successful treatment with clobetasol propionate. Quantitative information on remission and relapse of psoriasis can be obtained by multiparameter flow cytometry.