Our patient was 25 years old when she migrated to our country from China. Her medical and childhood history was scant although both the patient and her mother insist these were uneventful and that she had been an average student in school. The patient presented to our hospital at the age of 28 years old for seizures and altered behaviour. She was described by her husband to be responding slowly when spoken to. These episodes were interspersed by verbal and physical aggression, violent outbursts, or hypersomnolence (sleeping for >24 hours) with urinary incontinence. Computed tomography (CT) and magnetic resonance imaging (MRI) of the head were normal. Electroencephalography performed during episodes of hypersomnolence was compatible with global moderate diffuse encephalopathy. Arterial ammonia (195 mmol/L) and lactate (4.5 mmol/L) levels were markedly elevated. However, other liver tests and imaging were not suggestive of liver cirrhosis and excluded the presence of any portosystemic shunt. CT imaging revealed an atrophic pancreas. Tests for hepatitis B, hepatitis C, HIV, Wilson disease, systemic autoimmune disease, and syphilis were negative. In view of her significant behavioural change and elevated ammonia levels, she was screened for inborn errors of metabolism. Citrulline levels in the blood (939 umol/L) and urine (19.6 umol/mmol) were elevated 15-fold and 5-fold, respectively. There was corresponding elevated plasma arginine and threonine : serine ratios. She was commenced on L-arginine 1 g QDS and high-dose lactulose therapy which reduced the frequency of her violent outbursts and reduced the hypersomnolent episodes to once per fortnight. However, these episodes became increasingly difficult to control despite L-arginine replacement. By 2009, she was encephalopathic/hypersomnolent as often as 3 to 4 times per week. The frequency and nature of these episodes also made drug compliance difficult and affected her daily activities. Orthotopic liver transplantation (LT) from a deceased donor was performed in January 2010. The explanted liver was slightly enlarged measuring 21 x 16 x 7.5 cm and weighed 1.036 kg. The gross cut sections appeared pale brown, and the liver emitted a peculiar sweetish odour (Figure 1). Histology showed regenerative changes with alternating atrophied and hyperplastic liver plates. Mild lobular inflammation with ballooning change in the hepatocytes was demonstrated. No significant steatosis or fibrosis was seen (Figure 2). Immunosuppression consisted of prednisolone, tacrolimus, and mycophenolate mofetil. She has recovered well after LT, without further episodes of encephalopathy/hypersomnolence despite a normal protein diet. Arterial ammonia levels (23 umol/L) normalised less than 2 weeks after LT. As her sensorium and ammonia levels had returned to normal and she was able to function in the mental capacity of a normal healthy person, citrulline levels and excretion were not measured again after transplant. She is currently on tailing doses of dual immunosuppression (tacrolimus and mycophenolate mofetil). She continues to remain well more than 1 year after LT and has since returned to work.