Acute liver failure (ALF) refers to the sudden loss of liver function in patients without a prior history of chronic liver disease. This distinguishes ALF from end-stage chronic liver diseases, where liver failure can also occur. ALF is characterized by severe liver insufficiency (with jaundice and coagulation disorders) and encephalopathy. A precise definition is clinically significant, as the poor spontaneous prognosis of ALF occurs only when encephalopathy develops alongside severe liver dysfunction. ALF can be further classified based on the dynamics of its progression: fulminant ALF (within 7 days of liver failure and encephalopathy onset), acute ALF (8–28 days), and subacute or prolonged ALF (more than 4 weeks between jaundice and encephalopathy). These classifications help in prognosis assessment but have not been widely adopted in clinical practice. The causes of ALF are varied, with viral hepatitis and drug toxicity being the most common in Germany. Other less common causes include mushroom poisoning, acute manifestations of Wilson's disease, and Budd-Chiari syndrome. Hepatitis A (HAV) is relatively rare, but in northern European countries, it accounts for up to 20% of ALF cases. Hepatitis B (HBV) is more likely to lead to ALF, with a higher risk in women and in cases of concurrent hepatitis D (HDV) infection. HBV is not directly cytotoxic, but the immune response to the infection and the elimination of infected cells lead to ALF. The prognosis of ALF is poor, and the diagnosis is often made by detecting IgM antibodies against HBV core antigen (IgM-Anti-HBc). Hepatitis C (HCV) is a rare cause of ALF, while hepatitis E (HEV) is more common in Germany and is associated with a higher risk of ALF, especially in pregnant women. Cryptogenic hepatitis is common in subacute or prolonged ALF, with up to 90% of cases in some studies. Common causes of ALF include drug toxicity, especially paracetamol overdose, which is common in the UK but increasing in Germany. Paracetamol toxicity is dose-dependent, and severe liver damage can occur above 10–12 g. The metabolism of paracetamol through the p450 system leads to a toxic metabolite that is inactivated by glutathione. When glutathione is depleted, the metabolite accumulates, leading to cell damage. The prognosis of ALF is poor, with metabolic acidosis and early renal failure being unfavorable prognostic factors. Other causes of ALF include halothane hepatitis, an idiosyncratic drug reaction, and other drug-induced liver failure. The diagnosis of ALF is often based on clinical presentation, and the prognosis is influenced by the underlying cause, the patient's ageAcute liver failure (ALF) refers to the sudden loss of liver function in patients without a prior history of chronic liver disease. This distinguishes ALF from end-stage chronic liver diseases, where liver failure can also occur. ALF is characterized by severe liver insufficiency (with jaundice and coagulation disorders) and encephalopathy. A precise definition is clinically significant, as the poor spontaneous prognosis of ALF occurs only when encephalopathy develops alongside severe liver dysfunction. ALF can be further classified based on the dynamics of its progression: fulminant ALF (within 7 days of liver failure and encephalopathy onset), acute ALF (8–28 days), and subacute or prolonged ALF (more than 4 weeks between jaundice and encephalopathy). These classifications help in prognosis assessment but have not been widely adopted in clinical practice. The causes of ALF are varied, with viral hepatitis and drug toxicity being the most common in Germany. Other less common causes include mushroom poisoning, acute manifestations of Wilson's disease, and Budd-Chiari syndrome. Hepatitis A (HAV) is relatively rare, but in northern European countries, it accounts for up to 20% of ALF cases. Hepatitis B (HBV) is more likely to lead to ALF, with a higher risk in women and in cases of concurrent hepatitis D (HDV) infection. HBV is not directly cytotoxic, but the immune response to the infection and the elimination of infected cells lead to ALF. The prognosis of ALF is poor, and the diagnosis is often made by detecting IgM antibodies against HBV core antigen (IgM-Anti-HBc). Hepatitis C (HCV) is a rare cause of ALF, while hepatitis E (HEV) is more common in Germany and is associated with a higher risk of ALF, especially in pregnant women. Cryptogenic hepatitis is common in subacute or prolonged ALF, with up to 90% of cases in some studies. Common causes of ALF include drug toxicity, especially paracetamol overdose, which is common in the UK but increasing in Germany. Paracetamol toxicity is dose-dependent, and severe liver damage can occur above 10–12 g. The metabolism of paracetamol through the p450 system leads to a toxic metabolite that is inactivated by glutathione. When glutathione is depleted, the metabolite accumulates, leading to cell damage. The prognosis of ALF is poor, with metabolic acidosis and early renal failure being unfavorable prognostic factors. Other causes of ALF include halothane hepatitis, an idiosyncratic drug reaction, and other drug-induced liver failure. The diagnosis of ALF is often based on clinical presentation, and the prognosis is influenced by the underlying cause, the patient's age