Autoimmune hepatitis is a chronic, idiopathic disease of the liver, often seen in young to middle-aged women, characterised by interface hepatitis on histopathology, elevated immunoglobulins, particularly IgG, and the presence of autoantibodies in the serum, with hepatomegaly on imaging.
Description
Autoimmune hepatitis (AIH) is a chronic, inflammatory disease of the liver that occurs when the body’s immune system attacks liver cells. This immune response leads to inflammation and long-term damage to the liver. AIH is a rare condition that affects women more than men and can occur at any age.
Pathogenesis
AIH is characterised by immune-mediated injury to the liver’s parenchyma, resulting in chronic inflammation. The exact cause is unknown, but it’s thought to occur due to a combination of genetic predisposition, environmental triggers, and a dysregulated immune response.
Epidemiology, Risk Factors & Associations
AIH is relatively rare, with an estimated prevalence of 10-20 cases per 100,000 people in Europe. It predominantly affects women (75% of cases), and can present at any age, although peaks are often seen in young adulthood and around the fifth decade of life. There is an association with other autoimmune diseases, such as thyroiditis and rheumatoid arthritis.
Clinical Features
Clinical presentation of AIH can vary significantly. Some patients may be asymptomatic and the condition is discovered on routine blood tests, while others present with non-specific symptoms such as fatigue, jaundice, and arthralgia. Acute severe hepatitis or liver failure can be the first presentation in a minority of cases. Elevated serum liver enzymes and gamma globulins, particularly IgG, are typical laboratory findings.
Complications
If untreated, AIH can progress to cirrhosis and its associated complications including portal hypertension, hepatocellular carcinoma, and liver failure. AIH is also associated with a higher risk of cardiovascular disease and lymphoma.
Subtypes
AIH has two subtypes:
- Type 1 (the most common form) – Associated with anti-nuclear and/or smooth muscle antibodies.
- Type 2 – Associated with liver-kidney microsomal type 1 antibodies (anti-LKM1) or liver cytosol type 1 antibodies (anti-LC1), is more commonly seen in children.
Pathological Features
Histopathology
- Liver biopsy typically shows a dense lymphoplasmacytic infiltrate, interface hepatitis (also known as ‘piecemeal necrosis’), rosetting of liver cells, and emperipolesis.
- Focal or confluent necrosis can also be present.
- Chronic cases may show fibrosis or cirrhosis.
Biochemistry
- Elevated transaminases (AST, ALT)
- Increased serum IgG and positive autoantibodies (ANA, ASMA, or anti-LKM1) are typical biochemical features.
Genetics
- Certain HLA haplotypes are associated with AIH, particularly HLA-DR3 and HLA-DR4.
Radiological Features
General Features
- Radiological findings in AIH are non-specific and usually are indicative of the extent of the disease, such as cirrhosis or hepatocellular carcinoma.
- Liver ultrasonography, CT, and MRI may show hepatomegaly, nodular liver surface, and other signs of chronic liver disease.
Grading and Staging
AIH is graded according to the degree of inflammation and staged according to the extent of fibrosis. The revised original scoring system proposed by the International Autoimmune Hepatitis Group (IAIHG) is commonly used.
Differential Diagnosis
- Drug-induced liver injury
- Viral hepatitis
- Wilson disease
- Non-alcoholic steatohepatitis (NASH)
- Primary biliary cholangitis
- Primary sclerosing cholangitis
Management
AIH is primarily managed by gastroenterologists or hepatologists. Immunosuppressive therapy, typically with corticosteroids and azathioprine, forms the mainstay of treatment. In severe cases or if medical treatment is not successful, liver transplantation may be necessary. Regular follow-up with liver function tests and imaging is important for monitoring disease progression and response to treatment.