Autoimmune hepatitis (AIH) is a rare form of chronic hepatitis that predominantly affects women. Although the etiology is unclear, it is commonly associated with other autoimmune conditions (e.g., type 1 diabetes mellitus, celiac disease). Clinical presentation varies and patients may be asymptomatic or even show signs of acute liver failure. Diagnosis is established based on the detection of autoantibodies (especially anti-smooth muscle antibodies) and the histologic findings of liver biopsy. Treatment consists of immunosuppressive medications such as prednisone and azathioprine. The prognosis is favorable if patients are treated appropriately; without treatment, cirrhosis may develop.
- Type 1 AIH (80% of cases): characteristic autoantibodies include antinuclear antibodies (ANAs), anti-smooth muscle antibodies (ASMAs), anti-soluble liver antigen/liver pancreas antibodies (anti-SLA/LP)
- Type 2 AIH: characteristic autoantibodies include (anti-LKM-1), anti-liver cytosol antibodies-1 (ALC-1)
- Prevalence: 0.1–2/100,000 white adults in the US, even less so in other ethnicities 
Bimodal distribution: 10–20 years and 40–60 years 
- Type 1 AIH: most common in adults
- Type 2 AIH: most common in children
Sex: ♀ > ♂
- Type 1: (∼ 4:1) 
- Type 2: (∼ 10:1)
Epidemiological data refers to the US, unless otherwise specified.
AIH has an insidious onset in most patients and its presentation varies widely, ranging from asymptomatic disease to severe symptoms or even acute liver failure.
- Upper abdominal pain
- Weight loss
- Signs of acute liver failure (∼ ⅓ of patients)
- Laboratory tests
- Liver biopsy: Biopsy should be performed following the detection of AIH antibodies to confirm the diagnosis.
The differential diagnoses listed here are not exhaustive.
- Immunosuppressive medications
- Liver cirrhosis
- 10-year survival rate with treatment: > 90% 
- Type 2 AIH is associated with more severe disease, worse response to corticosteroids, and more frequent relapses.
- Increased risk of liver cirrhosis if left untreated