Liver/Kidney Microsome Antibody Type 1 and Hepatitis C Virus Infection

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Abstract
Recent studies have shown that hepatitis C virus antibodies are present in a large proportion of patients with autoimmune hepatitis type 2. We have studied 83 patients with liver/kidney microsome antibody–positive type 1 hepatitis. Hepatitis C virus antibodies were sought in every case by second–generation tests (hepatitis C virus enzyme–linked immunosorbent assay and recombinant immunoblot assay). Hepatitis C virus RNA sequences were sought in 22 patients (12 with recombinant immunoblot assay–positive results and 10 with recombinant immunoblot assay–negative results) by means of polymerase chain reaction and by use of primers located in the 5′ noncoding region. Sixty–four patients (77%) had positive results for hepatitis C virus antibodies in the enzyme–linked immunosorbent assay test, and 41 (49.3%) were confirmed by recombinant immunoblot assay. Hepatitis C virus RNA sequences were found in all the recombinant immunoblot assaypositive patients but in none of the 10 who were recombinant immunoblot assay–negative. The recombinant immunoblot assay–negative patients were younger than those who were positive (13 ± 11 vs. 50 ± 11 years) and had higher γ–globulin levels and liver/kidney microsome antibody–positive type 1 titers (61% had a titer of 1:1,000 or more, vs. only 17% of the recombinant immunoblot assay–positive patients). On the basis of these results, chronic hepatitis with liver/kidney microsome antibody–positive type 1 can be divided into two subgroups: (a) true autoimmune hepatitis type 2 (mainly observed in young women), with high titers of liver/kidney microsome antibody–positive type 1, and in which direct autoimmune mechanisms appear to be prominent; and (b) hepatitis C virus–associated hepatitis with liver/kidney microsome antibody–positive type 1 (generally affecting older patients, especially men), with low titers of liver/kidney microsome antibody–positive type 1, and in which the autoimmune process could be a consequence of hepatitis C virus infection. (Hepatology 1992;16:630-636.)