A 13-Month-Old With Xanthogranulomatous Pyelonephritis With Features of Renal Malakoplakia.

Xanthogranulomatous pyelonephritis is an uncommon chronic inflammatory renal disorder caused by chronic infection with gram-negative bacteria leading to destruction of the renal parenchyma and replacement with foamy lipid-laden macrophages. Renal malakoplakia is another rare form of chronic inflammatory granulomatous disease in the kidney associated with infection usually occurring in adults with immunocompromised status or debilitating disease. It is hallmarked by the finding of foamy histiocytes with distinctive basophilic inclusions (Michaelis-Gutmann bodies). We present a case of a 13-month-old male with history of congenital hydronephrosis who presented with clinical and radiologic findings suggestive of xanthogranulomatous pyelonephritis. However, further pathologic studies revealed the presence of Michaelis-Gutmann bodies, which are pathognomonic for renal malakoplakia. With this case we hope to bring further evidence to support that these two conditions are not mutually exclusive but rather represent two pathologic processes on the same disease spectrum.