Hyperammonemia syndrome in a liver transplant recipient due to <i>Ureaplasma parvum</i> : 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. <i>Ureaplasma</i> species, typically urogenital commensals, have recently emerged as important pathogens. We describe the first reported case of <i>Ureaplasma parvum</i>-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. <i>U. parvum</i> 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 <i>Ureaplasma</i> infection in post-orthotopic liver transplantation hyperammonemia and supports early empiric antimicrobial therapy to prevent fatal outcomes.