Xanthogranulomatous pyelonephritis in a 47-day-old male infant: a case report

Xanthogranulomatous pyelonephritis (XGP), a rare granulomatous renal disease linked to bacterial infection (e.g., Escherichia coli), presents challenges in pediatric diagnosis, especially in infants, due to overlap with neoplastic renal masses like Wilms tumor.

A 47-day-old male infant with fever, elevated inflammatory markers (WBC 13.94 × 10⁹/L, CRP 110.43 mg/L), and urinary leukocytes/hematuria showed a left renal mass (1.7 × 1.8 × 2.1 cm) on imaging. Biopsy revealed histiocytic-neutrophilic infiltration with focal necrosis, and metagenomic sequencing identified dominant E. coli. Antibiotic therapy (cefoperazone-sulbactam followed by cefdinir) induced regression (1.1 × 0.8 × 1.1 cm at 2 weeks). Elevated AFP (888.27 ng/ml) normalized, excluding malignancy.

This case highlights XGP as a critical differential diagnosis for febrile infants with renal masses. Integration of histopathology, metagenomic sequencing, and prolonged follow-up confirms that focal XGP can be managed successfully with targeted antibiotics, avoiding nephrectomy.