Infections, connective tissue diseases and vasculitis.

In genetically predisposed individuals, viruses, bacteria, or parasitic infectious agents are suspected of inducing autoimmunity and/or exacerbating autoimmune rheumatic diseases (ARD) once self-tolerance is broken. Although direct evidence for this association is still lacking, numerous data from animal models as well as from humans support the hypothesis of a direct contribution of pathogens to the induction of several ARD. This review focuses on the possible role of infectious agents as triggers of autoimmunity in systemic lupus erythematosus, polymyositis-dermatomyositis, antiphospholipid antibody syndrome, and primary vasculitis. Indeed, vasculitis may be a clinical manifestation of an infectious disease (secondary vasculitis). In addition, immune response abnormalities and immunosuppressive medications may be responsible for the high percentage of infectious complications in ARD patients. Recent therapeutic approaches aimed at lowering doses of cytotoxic agents and shortening duration of treatment with the most toxic drugs, have proved to be as effective as conventional regimens. New drugs and strategies aimed at preventing infections could further improve the outcome of ARD patients.