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

Abstract

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.

Keywords: Michaelis-Gutmann; anemia; hydronephrosis; malakoplakia; renal mass; xanthogranulomatous pyelonephritis.

Figure 1.

(A) Gross image of the right kidney, bivalved in fresh state: yellow arrow demonstrates collections of yellow-green purulent material in calyces; blue arrow demonstrates thickened white sclerotic renal capsule; red arrow demonstrates thinning of renal cortex. (B) Hematoxylin and eosin stained section of the kidney. Yellow bracket indicates the thickened capsule. Blue arrow indicates decreased perirenal adipose tissue. Original magnification, 25×. (C) Hematoxylin and eosin stained section. Yellow circle indicates granuloma formation with foamy histiocytes; orange dashed-circle indicates interstitial chronic inflammation. Original magnification, 200×. (D) Calcium von Kossa special stain. Insert: Targetoid structure represents a Michaelis-Gutmann body. Multiple concentric concretions in the histiocyte cell cytoplasm and in the extracellular spaces are circled in green. Original magnification, 200×.