Clinical and histologic heterogeneity of psoriatic plaques. Therapeutic relevance.

Twenty-three patients with resistant psoriasis vulgaris were evaluated clinically and histologically before and after treatment with potent topically administered steroids. It was shown that psoriatic plaques are comprised of clinically and histologically distinct acute and chronic areas, each responding differently to treatment. Chronic areas, characterized by chronic inflammation, respond well to therapy; acute areas, characterized by acute inflammation, are resistant to therapy. It is suggested that the psoriagenic stimulus is greater within the therapy-resistant "hot spots." Future therapy aimed at hot spots may aid in the better control of psoriasis.