Fever of unknown origin (FUO) in a renal transplant recipient due to drug fever from sirolimus.

INTRODUCTION: A variety of medications may cause drug fever. Drug fevers may persist for days to weeks until diagnosis is considered. The diagnosis of drug fever is confirmed when there is resolution of fever within 3 days after the medication is discontinued. Only rarely do undiagnosed drug fevers persist for over 3 weeks to meet fever of unknown origin (FUO) criteria. FUOs due to drug fever are uncommon, and drug fevers due to immunosuppressive drugs are very rare. CASE REPORT: This is a case of a 58-year-old female renal transplant recipient who presented with FUO that remained undiagnosed for over 8 weeks. DISCUSSION: We believe this is the first reported case of an FUO due to drug fever from sirolimus in a renal transplant recipient.