Xanthogranulomatous pyelonephritis in a child with autoimmune joint disease.

Xanthogranulomatous pyelonephritis is a rare condition in paediatric patients, mostly described in middle-aged female patients. We present a 7-year-old female with juvenile idiopathic arthritis, who was found to have a kidney mass with a concurrent Escherichia coli urinary tract infection. Surgical excision was done out of concern for possible malignancy. Histology confirmed the diagnosis of xanthogranulomatous pyelonephritis and persistent E. coli infection.