Psoriasis

Definition Psoriasis – Chronic, inflammatory disease of the skin characterized by altered epidermal growth and differentiation with multiple vascular and immunologic abnormalities – Still of unknown etiology

Pathophysiology Initial Lesions Increased edema and mononuclear cells in the upper dermis Slightly dilated venules in upper dermis w/ mononucl ear inflitrate Developing Lesion ~50% increase in epidermal thickness Increase in metabolic activity in the epidermis Mast cells, macrophages, T-cells and dendritic cells “marginal zone” Thickening of epidermis into a band- like pattern Parakeratosis, capillary elongation, rete ridges, lymphocyte, macrophage infiltration

Pathophysiology Mature Lesion Elongated rete ridges w/ thinned out epidermis on top. 100% basal layer mitotic activity Increased infiltration by lymphocytes, macrophages, dendritic cells, mast cells Involves various immune cells; e.g.: T-cells – specifically, CD4 and CD8+ cells which are rich in TNF-gamma. This indicates Th1 polarization Dendritic cells – plays a central but still unidentified role Macrophages – thought to fenestrate the epidermal basement membrane and also produces TNF-a Involves various cytokines and chemokines which show a polarization towards Th1 reponse; e.g. TNF-a, IFN-gamma – promotes keratinocyte proliferation

Co-morbidity Associated with an increased risk for obesity, metabolic syndrome and insulin resistance Increased risk for lymphoma but only for Hodgkin’s and cutaneous T-cell types No significant increase in risk for non- Hodgkin’s lymphomas