Abstract
Accurate diagnosis and treatment of febrile urinary tract infections (UTI) during childhood are important for the prevention of renal parenchymal damage and functional loss, and detection of underlying diseases related to chronic kidney disease (CKD). <i>Actinotignum schaalii</i> (<i>A. schaalii</i>)-related febrile UTI in children is rare, and its incidence and risk factors remain unclear. A 3-year-old boy with a history of UTI presented with fever and vomiting. Although the culture of his urine specimen in air was negative, <i>A. schaalii</i> was observed in a 5% carbon dioxide (CO<sub>2</sub>) culture condition, as well as an anaerobic one. A diagnosis of febrile UTI was made, and he recovered with antibiotic therapy. He was found to have CKD associated with vesicoureteral reflux (VUR) after further investigations. <i>A. schaalii</i> is one of the causative agents of febrile UTI in children with urinary tract abnormalities. Although the culture in the air could show negative results, urine culture in 5% CO<sub>2</sub> and anaerobic conditions is useful for diagnosis. Our case is the youngest and the first known case of <i>A. schaalii</i>-related febrile UTI associated with VUR in children.