Various types of immune-mediated liver diseases have been identified, such as autoimmune hepatitis (AIH), primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). AIH is a chronic disease where the immune system attacks the liver causing inflammation. If untreated AIH can progress to cirrhosis and liver failure. Two types of AIH have been identified; type I AIH is the most common form, whereas type II is less common and generally affects young girls. The specific type of AIH depends on the autoantibodies that are present and their target. PBC is an autoimmune disease characterised by the progressive destruction of the bile ducts in the liver leading to a build-up of noxious bile acids, which is known as cholestasis. PSC is a chronic cholestatic liver disease that is characterised by the intrahepatic and extrahepatic bile duct inflammation and fibrosis, which ultimately leads to bile duct strictures. PSC is highly heterogeneous and likely immune-mediated though the underlying aetiology is poorly understood. PSC ultimately progresses towards the development of cirrhosis, portal hypertension and hepatic decompensation.
How many have immune-mediated liver diseases?
The prevalence of AIH ranges from 4 – 42.9 cases per 100,000, some races show a greater genetic preponderance than others, e.g. Alaskan natives. PBC is most prevalent within northern Europe and the US, the prevalence of PBC in the general population is between 6.7-402 cases per million. PSC is more common in people of northern European descent, with a prevalence of 10 cases per 100,000 people..
How are immune-mediated liver diseases treated?
For the majority of patients AIH cannot be cured, consequently the disease is controlled through the use of immunosuppressive medication. AIH is treated through the use of immunosuppressive drugs such as prednisone and azathioprine. PBC is treated through the use of ursodeoxycholic acid (UDCA) and obeticholic acid (OCA). Treatment response is monitored through biochemical assessment, namely serum alkaline phosphatase (ALP) and total bilirubin. Currently, there is no specific treatment available for PSC. However, trials have indicated that UDCA may slow disease progression by increasing bile acid flow and reducing inflammation.
How are immune-mediated liver diseases diagnosed?
AIH diagnosis is based on histological abnormalities, clinical and biochemical findings and the presence of autoantibodies. A diagnosis of PBC requires the presence of at least two of the following criteria: a) biochemical evidence of cholestasis (i.e. high ALP levels), b) presence of anti-mitochondrial antibody (AMA) and c) histopathologic evidence of cholangitis and bile duct destruction. PSC is diagnosed through a combination of symptoms, biochemical tests and imaging of bile ducts, called a cholangiogram. Additionally, a liver biopsy may be needed to confirm the diagnosis and assess the severity of the disease.