How can I differentiate autoimmune hepatitis from other liver diseases based on clinical and laboratory findings?

Autoimmune hepatitis (AIH) can be differentiated from other liver diseases by a combination of clinical presentation and specific laboratory findings. Clinically, AIH often presents with nonspecific symptoms such as fatigue, malaise, and jaundice, but it may also be asymptomatic or present acutely with features resembling acute hepatitis; this contrasts with other liver diseases like viral hepatitis or alcoholic liver disease, which may have distinct exposure histories or risk factors NICE CG165 Czaja 2008.

Laboratory findings in AIH typically include elevated serum aminotransferases (ALT and AST) often markedly raised, hypergammaglobulinemia (especially elevated IgG), and the presence of characteristic autoantibodies such as antinuclear antibody (ANA), smooth muscle antibody (SMA), and liver-kidney microsomal antibody (LKM-1) NICE CG165 Carpenter & Czaja 2002. These autoantibodies help distinguish AIH from other causes of liver injury, which usually lack these markers.

Unlike viral hepatitis (e.g., hepatitis B or C), AIH patients test negative for viral serologies NICE CG165. Compared to non-alcoholic fatty liver disease (NAFLD) or alcoholic liver disease, AIH shows a more prominent autoimmune serologic profile and elevated IgG rather than metabolic or toxic injury markers NICE CG165 Hong et al. 2019.

Histological examination, although not a laboratory test per se, supports diagnosis by showing interface hepatitis with lymphoplasmacytic infiltrates, which is characteristic of AIH and helps differentiate it from other liver diseases NICE CG165 Carpenter & Czaja 2002.

In summary, the key differentiators of AIH are the presence of specific autoantibodies, elevated IgG, and characteristic histology combined with clinical features that may mimic other liver diseases but lack their typical risk factors or viral markers.