the development of hepatic encephalopathy in a patient without pre-existing liver disease. The liver must fail rapidly (typically within 26 weeks of the onset of jaundice), and the encephalopathy must develop within this time frame. This distinguishes ALF from acute-on-chronic liver failure (ACLF), where there is underlying cirrhosis.

In the UK, the most common causes of ALF are paracetamol overdose (accounting for over 50% of cases), idiosyncratic drug reactions (antibiotics, anticonvulsants, herbal remedies), acute viral hepatitis (hepatitis A, B, E — hepatitis C rarely causes ALF), autoimmune hepatitis, Wilson’s disease (in young patients presenting with haemolytic anaemia and liver failure), Budd-Chiari syndrome, and pregnancy-related liver disease (acute fatty liver of pregnancy, HELLP syndrome).