Pathogenetic studies in chronic urticaria. Failure to demonstrate vasculitis, complement activation and fibrinolysis.

To analyze the role of immune complexes, complement activation and fibrinolysis in chronic urticaria (CU), we performed serological, immunohistochemical and histopathological studies in 20 patients. In addition, the relationship to urticarial vasculitis was investigated. The results indicate that common CU is not associated with vasculitis. Neither circulating immune complexes nor immunoglobulin-complement complexes were found in the vessel walls. Lowered blood levels of complement and fibrinogen were found only in 1 and 3 patients, respectively. Alpha-2-antiplasmin and fibrin degradation products were within normal limits. Our study indicates that CU and urticarial vasculitis are separate entities. Complement activation and fibrinolysis do not appear to play an important role in CU.