Autoimmune hepatitis

Epidemiology

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Etiology

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• AIH is commonly associated with other autoimmune conditions
  • Type 1 AIH: Hashimoto thyroiditis, Grave disease, ulcerative colitis, celiac disease, rheumatoid arthritis
  • Type 2 AIH: Hashimoto thyroiditis, type 1 diabetes mellitus, vitiligo

Pathophysiology

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Classification

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• Type 1 AIH (80% of cases): characteristic autoantibodies include antinuclear antibodies (ANAs), anti-smooth muscle antibodies (ASMAs) anti-soluble liver antigen antibodies (anti-SLA)
• Type 2 AIH: characteristic autoantibodies include anti-liver-kidney microsomal-1 antibodies (anti-LKM-1), anti-liver cytosol antibodies-1 (ALC-1)

Clinical features

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Autoimmune Liver Diseases

Feature	Primary Sclerosing Cholangitis (PSC)	Primary Biliary Cholangitis (PBC)	Autoimmune Hepatitis (AIH)
Patho	Inflammation/fibrosis of intra- & extrahepatic bile ducts	Autoimmune destruction of intrahepatic bile ducts	Autoimmune destruction of hepatocytes
Epi / Assoc.	M > F (2:1), <40s Assoc: Ulcerative Colitis (IBD) (>80%)	F >> M (9:1), 40-60s Assoc: Sjögren’s, other autoimmune dz	F > M (3:1), bimodal (young/middle-aged) Assoc: Other autoimmune dz
Labs	Cholestatic: ↑↑ ALP, ↑ GGT	Cholestatic: ↑↑ ALP, ↑ GGT	Hepatocellular: ↑↑↑ AST/ALT (>1000s common), ↑ IgG
Serology	(+) p-ANCA	(+) AMA (Anti-Mitochondrial Ab)	(+) ANA, (+) ASMA (Anti-Smooth Muscle Ab)
Dx / Histo	MRCP/ERCP: “Beads on a string” Histo: “Onion skinning” periductal fibrosis	Normal imaging Histo: Florid duct lesion (lymphocytic cholangitis, granulomas)	Normal/nonspecific imaging Histo: Interface hepatitis, plasma cells
Tx	Symptomatic Tx; Liver transplant (definitive)	Ursodeoxycholic acid (UDCA)	Corticosteroids, Azathioprine
Key Risk	Cholangiocarcinoma, Colorectal Cancer (w/ UC)	Osteoporosis, Cirrhosis, HCC	Cirrhosis, Acute Liver Failure

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• Nonspecific symptoms
  • Fatigue
  • Upper abdominal pain
  • Weight loss
• Signs of acute liver failure (∼ ⅓ of patients)

Diagnostics

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Laboratory tests

• Liver chemistries: ↑↑↑ ALT and ↑↑ AST, ↑ GGT, normal or ↑ ALP, and ↑ bilirubin
• Serum antibodies
  • ANA, ASMA: combination is highly specific for type 1 AIH
  • Anti-LKM-1: typically positive in type 2 AIH
• SPEP: hypergammaglobulinemia (↑ IgG)

Liver biopsy

• Histological findings:
  • Lymphoplasmacytic interface hepatitis: ongoing inflammatory process with lymphocytic infiltration, bridging or multiacinar necrosis, and fibrotic changes
  • Bile duct changes (e.g., cholangitis, ductal injury)

Treatment

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