[Autoimmune and lymphoproliferative HCV-correlated manifestations: example of mixed cryoglobulinaemia (review)].

Mixed cryoglobulinaemia (MC) is a systemic vasculitis involving small vessels (arterioles, capillaries, venules). The histological hallmark of the disease is the leukocytoclastic vasculitis secondary to the vascular deposition of circulating immune-complexes (CIC), mainly cryoglobulins and complement. The immune-mediated vasculitic lesions are responsible for different MC clinical features, including cutaneous and visceral organ involvement. Hepatitis C virus (HCV) represents the triggering factor in the large majority of MC patients (>90%). Moreover, several epidemiological, clinico-pathological and laboratory investigations suggested a possible role for HCV in a wide spectrum of immuno-lymphoproliferative disorders; namely, porphyria cutanea tarda, diabetes, polyarthritis, lung fibrosis, poly-dermatomyositis, thyroiditis, thyroid cancer, B-cell non-Hodgkin's lymphomas (B-NHL), etc. Renal involvement with or without MC syndrome can be observed in HCV-infected individuals. There is great geographical etherogeneity in the prevalence of HCV-related disorders. This epidemiological observation suggests a multifactorial and multistep process in the pathogenesis of these conditions, involving other unknown genetic and/or environmental factors. HCV lymphotropism may explain the mono-oligoclonal B-lymphocyte expansion observed in HCV-infected individuals, particularly in MC patients. The 'benign' lymphoproliferative disorder, classified as monotypic lymphoproliferative disorders of undetermined significance (MLDUS), may be responsible for the wide production of CIC, including cryoglobulins, rheumatoid factor and different organ and non-organ specific autoantibodies. The consequence is the appearance of various HCV-related autoimmune diseases, including MC syndrome. This latter may be complicated by B-NHL in 10% of the cases; moreover, HCV infection has been confirmed in a significant percentage of 'idiopathic B-NHL. For a correct therapeutic approach to cryoglobulinaemic vasculitis, as well as to other HCV-related disorders, we should deal with concomitant, conflicting conditions: HCV infection, autoimmune and lymphoproliferative alterations. In this scenario, we can treat the diseases at three different levels by means of etiologic, pathogenetic and/or symptomatic therapies. The eradication of HCV by combined interferon and ribavirin therapy can be achieved in only a minority of cases. On the contrary, severe complications such as glomerulonephritis, sensory-motor neuropathy or diffuse vasculitis can be effectively treated by a combination of corticosteroids, plasma exchange and cyclophosphamide. More recently, a pathogenetic treatment with rituximab, a monoclonal chimeric antibody that binds to the B-cell surface antigen CD20 with selective B-cell blockade, was proposed in patients with HCV-related MC syndrome.