Recurrent Altered Mental State Associated with Nonhepatic Hyperammonemia Presented in an Elderly Female Patient: Probable Late-Onset Urea Cycle Disorder

Altered mentality associated with hyperammonemia is usually diagnosed in patients with liver disease. Nonhepatic hyperammonemia may be present in critically ill patients or may be caused by high protein diets or certain drugs. Urea cycle disorders (UCDs) rarely present with altered mentality with hyperammonemia in adult patients. An 82-year-old female visited our hospital with complaints of abnormal behavior and confusion. Routine blood tests revealed elevated serum ammonia. Her mentality and serum ammonia level normalized after lactulose enema and she was discharged thereafter. However, she was later re-admitted because of recurrent altered mentality. Amino acid analysis revealed that serum levels of ornithine and glutamine increased significantly, whereas the levels of alanine and glutamic acid increased slightly, and the levels of arginine, lysine, and citrulline were normal, which were probably caused by reduced activity of the mitochondrial ornithine carrier-1. Although our patient was not diagnosed genetically, this case illustrates the under-recognized fact that UCD can occur in a senile age. Clinical suspicion of UCDs in patients with hyperammonemia is critical for early diagnosis and to prevent the significant neurologic sequelae.