Autoimmune Hepatitis

Epidemiology and Etiology

Epidemiology

• Incidence: 0.9 to 2.0 per 100,000/year in Europe (no data available for the United States)
• More prevalent in females than males (4:1)
• Bimodal distribution: 1 peak at 10–20 years of age and another at 45–70 years

Etiology

Associated with other autoimmune conditions (e.g., Hashimoto’s thyroiditis, Graves’ disease, diabetes mellitus, rheumatoid arthritis, celiac disease, Sjogren’s syndrome)

Clinical Presentation

• Heterogeneous presentation that ranges from asymptomatic to acute liver failure and/or cirrhosis
• Early signs:
  • Fatigue, general malaise, and lethargy
  • Nausea
  • Abdominal pain
  • Hepatomegaly 
  • Weight loss
• Signs of acute liver failure: 
  • Jaundice
  • Right upper quadrant (RUQ) pain
  • Fever
  • Decreased platelet count

Diagnosis and Management

Diagnosis

Autoimmune hepatitis (AIH) is a differential diagnosis for any patient presenting with at least one of the following:

• Abnormal liver biochemical tests
• Acute hepatitis
• Cirrhosis
• Acute liver failure

Autoimmune hepatitis is a diagnosis of exclusion, so the first step is to rule out viral infection, drugs, metabolic, or genetic causes.

• Elevated transaminases (mild to > 1,000 U/L)
• Hypergammaglobulinemia (IgG is elevated)
  • Anti-smooth muscle antibody (ASMA) elevation is most characteristic.
  • Rarely, anti-LKM (liver kidney microsome) elevation may be seen, especially in children.
  • Antibodies against soluble liver antigen/liver-pancreas (SLA/LP) have been associated with severe AIH and poor outcome.
  • Less specific: elevated ANA (antinuclear antibody), RF (rheumatoid factor)
• Liver biopsy is the gold standard for diagnosis. It shows inflammation and necrosis in the periportal (zone 1) and interface area.

Management

• 40% mortality in 6 months without treatment
• Management primarily consists of immunosuppressive drugs:
  • Corticosteroids: to achieve remission (80% response rate) 
  • Steroid-sparing agent: Azathioprine is used as maintenance therapy as most patients relapse when corticosteroids are withdrawn.
  • Remission with optimal treatment should be achieved within 6 months.
  • Liver transplantation is indicated in cases of decompensated liver cirrhosis.
  • Follow-ups are recommended since these patients have an increased risk of developing hepatocellular carcinoma (HCC).

Differential Diagnosis

The following conditions are differential diagnoses of autoimmune hepatitis:

• Primary biliary cholangitis (PBC): also presents with fatigue, jaundice, hepatomegaly, and biopsy results similar to AIH. The characteristic presence of anti-mitochondrial antibodies (AMA) helps differentiate PBC from autoimmune hepatitis for which anti-smooth muscle antibodies (ASMA) are characteristic.
• Primary sclerosing cholangitis (PSC): also presents with fatigue, jaundice, hepatomegaly. One of the best ways to differentiate PSC from AIH is via imaging modalities such as MRCP (magnetic resonance cholangiopancreatography), which shows characteristic multifocal structuring and dilation of intrahepatic and/or extrahepatic bile ducts and seals the diagnosis of PSC.
• Viral hepatitis: The most commonly used method is the antibody/antigen detection in the serum. However, some patients with AIH may test false-positive for hepatitis C antibody; this can be confirmed by obtaining a hepatitis C virus RNA level in these patients. 
• Other causes of hepatitis (drug-induced, non-alcoholic steatohepatitis): also present with fatigue, jaundice, hepatomegaly, and RUQ tenderness. These causes must be ruled out using history and laboratory evaluation. The presence of ASMA is a strong indicator of AIH as the cause.