C) Hepatic encephalopathy

Acute liver failure (ALF) is defined as the acute onset of severe liver injury with encephalopathy and impaired synthetic liver function (defined as INR ≥ 1.5) in a patient without cirrhosis or preexisting liver disease. Hepatic encephalopathy describes the spectrum of potentially reversible neuropsychiatric abnormalities seen in patients with liver dysfunction. The presence of hepatic encephalopathy differentiates ALF from acute hepatitis, which usually has a better prognosis than ALF. Common causes of ALF include drug toxicity (e.g., acetaminophen overdose) and acute viral hepatitis. In this patient with chronic hepatitis B, superinfection with hepatitis D virus is a possibility, leading to ALF.

Answer choice A: Blood ammonia level > 100 µmol/L, is incorrect. While arterial and venous ammonia concentrations are often elevated in patients with hepatic encephalopathy, an elevated ammonia level is not required to make the diagnosis. In addition, elevated ammonia levels may be seen in patients who do not have hepatic encephalopathy.

Answer choice B: Elevated serum alpha-fetoprotein, is incorrect. Elevated serum alpha-fetoprotein is associated with hepatocellular carcinoma and other liver conditions but is not specific for ALF.

Answer choice D: Serum cerulopolasmin level < 20 mg/dL, is incorrect. Low serum ceruloplasmin level is seen in Wilson disease, a hereditary condition causing liver and neurologic dysfunction.

Answer choice E: Serum ferritin level > 1,000 ng/mL, is incorrect. Elevated serum ferritin levels are seen in conditions like hemochromatosis, an iron-overload disorder, not specific to ALF.

Key Learning Point

Acute liver failure (ALF) is diagnosed by the presence of hepatic encephalopathy and impaired synthetic liver function (INR ≥ 1.5) in a patient without preexisting cirrhosis or liver disease.