Platelet function in cutaneous diseases.

Blood platelets participate actively in immune-inflammatory processes. Responding to the variety of stimuli such as cell activation leads to the release of several mediators, including RANTES, platelet factor 4, beta-thromboglobulin, thymus and activation-regulated chemokine (TARC/CCL17), serotonin and arachidonic acid metabolites. It also affects the expression of immunomodulatory and adhesive molecules, including CD154 and P-selectin. Immune-inflammatory processes associated with skin diseases could induce platelet activation, which, in turn, would contribute to acceleration and modulation of these processes. Activated platelets are capable of facilitating leukocyte rolling in the skin and the release of skin inflammation mediators. Changes in platelet function and behaviour may occur in certain types of skin inflammatory conditions and platelets might then be an important effector cell of the skin immune system, contributing to the pathogenesis of some skin inflammatory disorders. The changes in platelet activity and reactivity have been demonstrated to show distinctly different pathogenic mechanisms in cutaneous diseases, such as urticaria, atopic eczema/dermatitis syndrome and psoriasis. Considering the risk of cardiovascular events, some of them seem to be of clinical significance. This contribution is a brief outline of the present knowledge of the platelet function in dermal disorders.