Figure 741

Malakoplakia. Malakoplakia (or malacoplakia), like xanthogranulo-matous pyelonephritis, is also a consequence of abnormal macrophage response to gram-negative bacteria, A. Malakoplakia occurs in association with chronic UTI [14]. In more than 20% of cases, affected persons have some evidence of immunosuppression, especially corticos-

teroid therapy for autoimmune disease. In 13% of the published cases, malakoplakia involved a transplanted kidney. The female-male ratio is 3:1. Lesions can involve the kidney, the bladder, or the ureter and form pseudotumors. B, Histologically, malakoplakia is distinguished by large, pale, periodic acid-Schiff-positive macrophages (von Hansemann cells) containing calcific inclusions (Michaelis-Gutmann bodies). The larger ones are often free in the interstitium. Malakoplakia, an unusual form of chronic tubulointerstitial nephritis, must be recognized by early renal biopsy and can resolve, provided treatment consisting of antibiotics with intracellular penetration is applied for several weeks. (B, Courtesy of Gary S. Hill, MD.)

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