Activation of blood coagulation in chronic urticaria: pathophysiological and clinical implications.

Chronic urticaria (CU) is a skin disorder characterized by the recurrent eruption of short-lived wheals accompanied by redness and itching for at least 6 weeks. The wheals can be associated with angioedema. CU is considered an autoimmune disease in about 50% of cases with the presence of circulating histamine releasing autoantibodies mainly directed against the high affinity IgE receptor FcepsilonRI on mast cells and basophils or against IgE. In several CU cases regarded as idiopathic; the actual pathophysiological mechanisms are still unknown. Some patients with CU do not respond to antihistamines and require the use of systemic steroids or cyclosporin, which are, however, not always effective. In CU, several investigators have demonstrated the activation of coagulation that is due to the involvement of eosinophils and a tissue factor pathway with generation of thrombin potentially contributing to an increased vascular permeability. CU patients often present with elevation of coagulation and fibrinolysis markers, such as prothrombin fragment F1+2 and D: -dimer, which correlate with the disease severity. Preliminary data indicate that anticoagulant treatment with heparin and warfarin may be effective in reducing the symptoms of this disorder. Taken together, all these findings provide the rationale for proposing clinical trials on the use of anticoagulant drugs as adjuvant treatment in CU patients.