Case Report: Hemorrhagic fever with renal syndrome caused by Seoul orthohantavirus mimicking severe acute pancreatitis: dynamic imaging evolution and pathogen confirmation by mNGS

Background Hemorrhagic fever with renal syndrome (HFRS) is a zoonotic disease caused by orthohantaviruses, characterized by fever, thrombocytopenia, renal impairment, and capillary leak syndrome. Its atypical presentations can closely mimic acute pancreatitis (AP), posing substantial diagnostic challenges. Case presentation A 33-year-old man presented with fever, vomiting, and watery diarrhea. Initial computed tomography (CT) revealed peripancreatic and perirenal exudation suggestive of severe acute pancreatitis. He already had profound thrombocytopenia on admission (nadir 29 × 10⁹/L), progressive renal impairment, hematuria, and proteinuria, without typical pancreatitis risk factors or elevated pancreatic enzymes. Contrast-enhanced CT demonstrated progressive retroperitoneal exudation with relatively mild pancreatic parenchymal changes and newly developed bilateral pleural effusion. Whole-blood metagenomic next-generation sequencing (mNGS) detected high-copy Seoul orthohantavirus, with concurrent hepatitis B virus. The patient recovered fully with supportive care, intravenous immunoglobulin, and symptomatic treatment; pre-discharge ultrasound showed normal pancreatic morphology. Conclusion Seoul orthohantavirus infection can closely mimic severe acute pancreatitis clinically and radiologically. Disproportionate thrombocytopenia, renal involvement, and progressive retroperitoneal exudation with preserved pancreatic parenchyma are key diagnostic clues, and mNGS enables early definitive pathogen confirmation, facilitating appropriate management.