Xanthogranulomatous pyelonephritis in an adolescent.

Xanthogranulomatous pyelonephritis is a chronic, inflammatory disease of the kidney rarely found in the pediatric population. We report the case of a 16-year-old boy with fever, microscopic hematuria, and an enlarging cystic renal mass on ultrasonography. The patient had no evidence of renal stones and no known risk factors, other than a recent tattoo performed with unsterile equipment. Because the differential diagnoses included Wilms tumor, he underwent open exploration and nephrectomy. The histopathologic findings were consistent with xanthogranulomatous pyelonephritis, and cultures grew methicillin-resistant Staphylococcus aureus. The etiology was believed to be bacterial seeding from the unsterile tattoo.