Type II cryoglobulinemia is not associated with hepatitis C infection: the Dutch experience

Mixed cryoglobulinemia (MC) are cryoprecipitable immunocomplexes. In type II MC, a combination of polyclonal and monoclonal immunoglobulins is found, whereas in type III a combination of polyclonal immunoglobulins is detected. MC is usually associated with hepatitis C (HCV) infection as has been found in studies that have been performed in countries with a high prevalence of HCV. Because HCV has an extremely low prevalence in the Netherlands (<0.1% of the population), we wondered whether HCV is also associated with MC in our regional referral center. To answer this question, we tested consecutive patients with type II MC for HCV antibodies and for HCV-mRNA by polymerase chain reaction (PCR). Between January 2000 and June 2005, 22 patients tested positive for type II MC. Seven patients had essential MC, 2 patients had MC due to a lymphoproliferative disease, 10 patients had MC in the context of a systemic autoimmune disease, and 3 patients had MC without a clear diagnosis. HCV antibodies were not detected in any of the 22 patients. Also, all samples tested negative for HCV-mRNA. During follow-up none of these patients developed an HCV infection. In summary, the estimated occurrence of HCV in 60-90% of patients with MC is not found in our region where MC is only infrequently associated with HCV. In a substantial proportion of our patients a really "essential MC" is observed. A search for yet unknown etiological factors is clearly needed in these patients, who frequently have severe renal involvement warranting aggressive immunosuppressive therapy.