When the Unseen Strikes: Acute Fungal Pyelonephritis with Elusive Etiology in a Healthy Paediatric Patient

Abstract Acute fungal pyelonephritis is extremely rare in healthy children, with most paediatric cases caused by bacteria. Fungal urinary tract infections constitute only 5–7% of cases, usually in immunocompromised patients or those with urinary tract abnormalities or instrumentation. We describe an extraordinary case of a 9-year-old healthy boy with no history of urinary tract abnormalities, prolonged antibiotic use, or immunodeficiency, who presented with fever, vomiting, and abdominal pain. He was started on empirical antibiotics but failed to respond. After exhaustive evaluation, renal biopsy revealed fungal pyelonephritis. Thus, a high index of suspicion for fungal pathogens is crucial when pyelonephritis fails to respond to initial antibacterial therapy.