Type I membranoproliferative glomerulonephritis and HCV infection.

Type I membrano-proliferative glomerulonephritis (MPGN) is secondary to chronic bacterial, parasitic, viral (HB) infections, to autoimmune disorders or primary or malignant haemopathies. MPGN are thought to be linked to the deposition of immune complexes preformed in the circulation or formed in situ in the glomeruli. A link between HCV and type I MPGN was reported for the first time in 1993. In some patients, the renal clinical pattern is the most obvious (nephrotic syndrome) whereas in others liver disease or cryoglobulinaemia prevail. A risk factor of HCV infection exists in 80% of cases. Renal biopsy and scanning electron microscopy usually substantiate cryoglobulinaemia. Circulating cryoglobulins are most often detected, usually of type II. CH50 is decreased in 90% of patients and rheumatoid factors have been found in two-thirds of patients. The cryoprecipitate contains viral RNA and anti-HCV antibodies. The viral RNA is nearly always found in the cryoprecipitate. Analysing the viral genotype does not elicit predominance of any particular type. Viral genome detection in renal biopsy specimens appears to be technically difficult. Type I MPGN secondary to HCV infection appear to be improved by interferon-alpha therapy but treatment suspension is immediately followed by the recurrence of viraemia and nephrotic syndrome. Serological tests to detect anti-HCV antibodies and viral RNA by PCR in type I MPGN, so far considered as 'primary', are scarce and produce conflicting results: there might be a link between those glomerulopathies and HCV infection in the USA and in Japan only, not in Europe.