Current Evidence ALF in children can be secondary to a variety of causes, however all result in the progression of irreversible hepatocyte injury In children younger than year of age, ALF most commonly occurs in the setting of a metabolic disease such as urea cycle disorders, galactosemia, type I tyrosinemia, or an underlying mitochondrial disorder (see Chapter 95 Metabolic Emergencies ) Other causes include viral hepatitis such as herpes simplex or enterovirus and medications such as acetaminophen In children older than year of age, the etiology is not determined in half of all cases ( Table 91.5 ) In identified cases, pharmaceutical agents such as acetaminophen or antiepileptic drugs are the most common causes Importantly, prolonged and inappropriate acetaminophen dosing is likely an important contributor to ALF in children, however it is much more difficult to assess with current testing mechanisms, which more accurately assesses for acute toxicity (see Chapter 102 Toxicologic Emergencies ) Metabolism of acetaminophen is known to be quite variable, and there are likely patients who are slow metabolizers that may increase their risk of ALF with prolonged use, even when correct weightbased dosing is given Other causes include autoimmune hepatitis and infections such as viral hepatitis Herbal drugs have also been known to cause ALF In developing countries, viral hepatitis is by far the most common etiology of ALF in all age groups of children