Response of the clinically uninvolved skin of psoriatic patients to standardized injury.

Test sites on healthy controls and on the clinically uninvolved skin of psoriatic patients were stripped with tape, and eight variables were quantified at intervals during the subsequent healing process. In the control groups, the stratum corneum regenerated at a constant rate and the underlying skin showed elevations of metabolic activity peaking around days 2-4. In the psoriatic groups, we observed that (I) the response of the keratinizing zone is identical to that of the controls, (2) the proliferative response is initially normal but remains elevated rather longer than usual, and (3) the dermal capillaries (indicated by alkaline phosphatase activity) show a gross hyper-reactivity which is already apparent after 1 day and which persists for more than a week. These findings support our previous conclusion that metabolic alteration of the dermal capillary precedes epidermal hyperplasia in the pathogenesis of the psoriatic lesion.