Autoimmune hepatitis In Japan: epidemiology and clinical features

The number of patients with autoimmune hepatitis (AIH) who received medical treatment in 1995 was estimated to be 6,800 (5,000-7,500), representing 2% of the total number of patients with chronic hepatitis and/or liver cirrhosis in Japan. In the latest nationwide survey on autoimmune hepatitis conducted in 1997, in which 413 patients were enrolled, male-to-female ratio was 1:6.2 and the mean age was 54.2 +/- 13.4 (SD) years with a single peak in the sixth decade with respect to the age distribution. The positive outcome rates of antiHCV and HBsAg were 7.3 and 0.6%, respectively. The latter was not significantly different from that in blood donors in Japan. Twenty-nine of 30 patients positive for antiHCV were examined for serum HCV-RNA. Sixteen of them were positive for HCV-RNA. Thus, HCV carrier rate in patients with AIH was about 3%, significantly higher than in blood donors. Ninety-eight percent of the patients enrolled in the survey were positive for antinuclear antibody and/or antismooth muscle antibody and classified into type 1 AIH. No patients were examined for LKM-1 antibody. HLA-DR4 was positive 74.4% patients. No patients had HLA-DR3. Corticosteroid was used in 78% of the patients enrolled and normalization of ALT and AST was induced in 89% of them. Autoimmune hepatitis (AIH) is one of the chronic liver diseases in which autoimmune mechanism plays an important role in the perpetuation of liver injury. Nationwide surveys on AIH started in 1975, when the research group of AIH was set up as a subdivision of the Research Group on Intractable Hepatitis supported by Japanese Ministry of Public Health and Welfare. Since then, several nationwide surveys has been conducted, revealing the actual state of AIH in Japan. However, we had found lots of difficulty in differentiating AIH from viral hepatitis, especially non-A, non-B hepatitis (NANB hepatitis), because of the prevalence of the latter in our country. This difficulty was overcome by identification of HCV-RNA in 1989. Furthermore the diagnostic criteria proposed by International AIH group in 1993 enabled us to study and discuss AIH on the worldwide common base [1]. The scoring system of diagnostic criteria by International AIH group was applied to the patients enrolled in 1997 survey (Table 1). The score (AIH score) was 10 to 15 in 165 of 413 (40.0%) and 16 or higher in 212 (51.3%) [2]. In this article, the epidemiological and clinical aspects or AIH in Japan will be discussed mainly based on the data obtained in the nationwide surveys conducted after the diagnostic system for HCV infection was introduced in the routine clinical practice [2,3].