Non HCV-related mixed cryoglobulinemia

A striking association (>90%) between mixed cryoglobulinemia (MC) and hepatitis C virus (HCV) infection has been established by means of clinico-epidemiological and laboratory studies. However, little information is available as regards the etiopathogenesis and the actual percentage of HCV-negative MC. This latter seems to be more frequent in the same geographical areas where the overall prevalence of MC is low. In 195 Italian patients with serum mixed cryoglobulins consecutively analyzed at the laboratory of our hospital, during one year, the prevalence of HCV-negative MC was 15.9%. Moreover, we evaluated the clinico-serological characteristics of our whole series of 65 HCV-negative MC patients: "essential" MC was present in only 25%, while the majority of cases showed different connective tissue diseases or neoplastic disorders. Interestingly, patients with Sjögren's syndrome or lymphoma had higher levels of cryocrit with cryoglobulinemic syndrome comparable to that found in HCV-positive MC patients. MC is a multifactorial disorder; considering possible etiological factors and clinical associations the disease may present different subsets: the prevalent group of HCV-positive MC; HCV-positive MC associated with different autoimmune lymphoproliferative disorders; two MC subsets without any apparent causative agent: those with well-known autoimmune lymphoproliferative disorders and the rare cases of "essential" MC; and finally MC associated with other infectious agents.