Abstract: Objective The aim of this study was to analyze the clinical and liver histopathological features of patients with autoimmune hepatitis (AIH) with serum normal alanine aminotransferase (ALT) and low immunoglobulin G (IgG) levels. Methods 61 patients with AIH were admitted to Traditional Chinese Medicine Hospital Affiliated to Xinjiang Medical University between January 2015 and December 2021, and the clinical and liver biopsy materials were retrospectively collected, including demographic information, medical history, blood routine, liver function tests, immunoglobulin G(IgG), antinuclear antibody (ANA). Results Serum alkaline phosphatase (ALP) levels were 93.7(71.0, 161.0)U/L and 193.6(41.0, 320.4)U/L, GGT levels were 27.9(18.3, 104.2)U/L and 158.8(62.2, 293.2)U/L, total serum bilirubin levels were 18.7(12.8, 26.0)μmol/L and 28.4(16.5, 45.9)μmol/L, aspartate aminotransferase-to-platelet ratio index (APRI) were 0.5(0.3, 1.7) and 3.1(1.1, 5.1), GGT/platelet ratio were 0.2(0.1, 1.4) and 0.8(0.4, 1.9), significantly different between patients with normal and elevated serum ALT levels(P＜0.01); the percentages of histological activity index greater than G2 were 45.0% and 56.1%, liver fibrosis greater than S2 were 55.0% and 41.5%, interfacial inflammation accounted for 90.0% and 100.0%, plasma cell infiltration accounted for 80.0% and 90.2%, and rose-rosette changes accounted for 25.0% and 19.5%, not significantly different between the two groups (P＞0.05); there was no significant difference as respect to liver histopathological changes between patients with low serum IgG level and those with elevated serum IgG level (P＞0.05); there were significant differences respect to serum ALP, GGT, TBIL, APRI and GGT/PLT ratio (P＜0.01)between patients with normal serum ALT and low IgG level and those with elevated serum ALT and IgG levels, while there was no significant difference as respect to liver histopathological changes between them (P＞0.05). Conclusions Serum biochemical and serological indexes could not accurately reflect the disease severity in patients with AIH, and we recommend liver biopsy in AIH patients with low serum IgG and normal ALT.

Key words: Autoimmune hepatitis, Alanine aminotransferase, Immunoglobulin G, Liver histopathology