Autoimmune hepatitis (AIH) is a chronic, progressive inflammatory liver disease of unknown etiology.

Epidemiology

• Incidence - 2/100,000
• Sex - F:M; 3:1
• Type 1 - most common form of AIH
  • Also referred to as classic, active chronic, lupoid, plasma cell, or autoimmune chronic active hepatitis
  • Typically seen in young women
  • Age - bimodal peaks (10-20 years, 45-70 years)
• Type 2
  • Often seen in children and persons from Mediterranean countries
  • May be seen in association with chronic hepatitis C infection
  • Disease has a rapid onset and progression
• Type 3
  • Least common form of AIH
  • Typically seen in young women
  • Similar disease course to AIH, type 1

Clinical Presentation

• Nonspecific - fatigue, lethargy, anorexia, malaise
• Gastrointestinal - nausea, abdominal pain, jaundice, hepatomegaly
• Musculoskeletal - arthralgias

Treatment

• Therapeutic response to anti-inflammatory therapy may be the only indication of AIH in those patients
• Treatment differs dramatically for AIH compared to viral hepatitis
  • Immunosuppression used for AIH can be harmful in cases of viral infection and treatment with interferon may cause a worsening of AIH
  • Immunosuppressive treatment is essential in AIH to prevent liver fibrosis and cirrhosis

Diagnosis

• No single diagnostic test for AIH
  • Requires evaluation of clinical, laboratory, and histological findings as well as the exclusion of other causes of chronic hepatitis
  • Presenting symptoms can be quite varied -  about 10-30% of patients with clinical features of AIH do not show significant titers of antibodies to any of the markers
• Laboratory Testing
  • Abnormal liver function tests
  • Elevated gammaglobulins
  • May have positive ANA homogenous pattern, rheumatoid factor
  • Antibodies
    • LKM-1 antibodies
      • React uniformly with cytochrome P450 2D6, a 50kDA protein found in the cytoplasm of all hepatocytes and renal proximal tubular cells
      • In the U.S., LKM-1 antibodies are common in pediatric patients and rare in adults
      • LKM-1 antibodies occur in only 4% of adults with AIH
    • Smooth muscle antibodies (F-actin)
      • SMA antibodies are the hallmark of AIH type 1
      • Also seen in chronic hepatitis
      • Testing LKM positive patients for ANA and SMA may be helpful in distinguishing between type 1 and type 2 AIH
    • Soluble liver antigen (SLA)
      • The presence of SLA antibodies has almost 100% specificity for autoimmune hepatitis, although only 12-30% of patients have these antibodies

Differential Diagnosis

• Primary biliary cirrhosis (PBC)
• Primary sclerosing cholangitis (PSC)
• Chronic hepatitis
• Wilson disease
• Hemochromatosis