Hyperammonemia syndrome in a liver transplant recipient due to Ureaplasma parvum: a case report

Hyperammonemia syndrome is a rare, life-threatening complication following orthotopic liver transplantation. While most cases result from graft dysfunction, metabolic disorders, or portosystemic shunting, infectious etiologies are infrequently recognized. Ureaplasma species, typically urogenital commensals, have recently emerged as important pathogens. We describe the first reported case of Ureaplasma parvum-associated hyperammonemia syndrome following isolated orthotopic liver transplantation. A 63-year-old man developed severe hyperammonemia and encephalopathy on postoperative day 14, despite preserved graft function and embolization of a large splenorenal shunt. In the absence of other causes and with rapid clinical decline, empiric doxycycline was initiated. U. parvum was subsequently detected via bronchoalveolar lavage and plasma cell-free DNA testing. Continued doxycycline led to normalization of ammonia levels and neurologic recovery. This case underscores the importance of considering Ureaplasma infection in post-orthotopic liver transplantation hyperammonemia and supports early empiric antimicrobial therapy to prevent fatal outcomes.