Adult-Onset Focal Bacterial Nephritis Without Urinary Symptoms Presenting With Systemic Toxic Rash: A Report of a Rare Case

Focal bacterial nephritis (FBN) is a localized bacterial infection of the kidney, representing an intermediate stage between acute pyelonephritis and renal abscess. It is usually accompanied by urinary symptoms, and adult cases without such symptoms are rare. We report a 31-year-old woman with a history of atopic dermatitis who presented with high fever and a generalized toxic rash but no urinary tract symptoms. Laboratory data showed leukocytosis, markedly elevated inflammatory markers, and disseminated intravascular coagulation. Urinalysis was normal, but blood cultures were positive for methicillin-sensitive <i>Staphylococcus aureus</i> (MSSA). Contrast-enhanced computed tomography revealed multiple wedge-shaped perfusion defects in the right kidney, consistent with FBN. Echocardiography excluded endocarditis or embolic sources. The patient was treated with cefepime followed by a four-week course of cefazolin, resulting in complete clinical recovery and radiological improvement. No recurrence was observed during follow-up. This case illustrates that MSSA bacteremia can lead to FBN even in the absence of urinary symptoms. Early recognition and prompt imaging are crucial for diagnosis. Furthermore, systemic toxic rash may serve as an early clinical clue to underlying bacteremia.