What are the markers for Autoimmune Hepatitis (AIH)?

From the Guidelines

Autoimmune hepatitis is diagnosed using several serological markers, including anti-nuclear antibody (ANA), anti-smooth muscle antibody (ASMA), anti-liver kidney microsomal antibody (anti-LKM-1), and anti-soluble liver antigen/liver pancreas antigen (anti-SLA/LP), with serum IgG levels also being a useful marker. The diagnosis of autoimmune hepatitis (AIH) requires a combination of clinical, laboratory, and histological features, as well as the exclusion of other liver diseases. According to the most recent guidelines, the simplified diagnostic criteria for AIH include the presence of ANA, SMA, or anti-LKM-1 antibodies at titers ≥1:40, elevated serum IgG levels, and characteristic liver histology features such as interface hepatitis and lymphoplasmacytic infiltration 1.

The markers for AIH can be summarized as follows:

• Anti-nuclear antibody (ANA)
• Anti-smooth muscle antibody (ASMA)
• Anti-liver kidney microsomal antibody (anti-LKM-1)
• Anti-soluble liver antigen/liver pancreas antigen (anti-SLA/LP)
• Elevated serum IgG levels
• Characteristic liver histology features, such as interface hepatitis and lymphoplasmacytic infiltration

It is essential to note that the diagnosis of AIH requires a comprehensive evaluation, including a thorough medical history, physical examination, laboratory tests, and liver biopsy, to exclude other liver diseases and confirm the diagnosis. The presence of these autoantibodies and elevated IgG levels reflects the immune-mediated nature of the disease, where the body's immune system attacks hepatocytes. However, antibody titers do not always correlate with disease severity, and some patients may be seronegative despite having the disease.

In clinical practice, the diagnosis of AIH should be based on the most recent and highest-quality evidence, which emphasizes the importance of a comprehensive diagnostic approach, including serological markers, liver histology, and exclusion of other liver diseases 1.

From the Research

Markers for Autoimmune Hepatitis (AIH)

The markers for Autoimmune Hepatitis (AIH) can be categorized into two main types: AIH type 1 and AIH type 2.

• AIH type 1 is characterized by the presence of:
  • Antinuclear antibodies (ANA) 2, 3, 4, 5, 6
  • Smooth muscle antibodies (SMA) 2, 3, 4, 5, 6
  • Antineutrophil cytoplasmic autoantibodies (ANCA) 2, 5
  • Antibodies against the asialoglycoprotein receptor (anti-ASGP-R) 2, 5
  • Antibodies to soluble liver antigens or liver-pancreas (anti-SLA/LP) 2, 3, 4, 5
• AIH type 2 is characterized by the presence of:
  • Anti-liver kidney microsomal antibody type 1 (anti-LKM-1) 2, 3, 4, 5, 6
  • Anti-liver cytosol type 1 (anti-LC1) 2, 3, 4, 5
  • Anti-liver kidney microsomal antibody type 3 (anti-LKM-3) 2, 5

Target Autoantigens

The target autoantigens for these markers have been identified as:

• Cytochrome P450 2D6 (CYP2D6) for anti-LKM-1 autoantibodies 2, 5
• Family 1 of UDP-glycuronosyltransferases for anti-LKM-3 autoantibodies 2, 5
• A 50 kDa protein for anti-SLA/LP autoantibodies 2, 5
• Formiminotransferase cyclodeaminase for anti-LC1 autoantibodies 2, 5
• Cytochrome P450 1A2 for anti-LM autoantibodies 5