Kawasaki disease complicated with acute focal bacterial nephritis

We report a young child who contracted acute focal bacterial nephritis (AFBN) in the acute phase of Kawasaki disease (KD). She was initially admitted with a diagnosis of KD with pyuria, which was interpreted as one of the findings typically characteristic of KD. Her fever resolved after the first intravenous immunoglobulin (IVIG) treatment. However, her fever recurred and did not respond to the second IVIG. Additional history revealed several episodes of fever of unknown origin and vesicoureteral reflux in her relatives. This led us to re-examine the urinalysis and perform a contrast-enhanced CT, which revealed urinary tract infection and AFBN. This case highlights the importance of careful history-taking and continuously reviewing the differential diagnosis for other potential sources of fever throughout KD treatment.