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August 15, 2017

Megalocytic Interstitial Nephritis

This biopsy shows a chronic active interstitial nephritis with numerous interstitial foamy macrophages containing abundant PAS-positive cytoplasmic granules (Fig 1-3).  The findings are consistent with megalocytic interstitial nephritis.  Megalocytic interstitial nephritis is an entity closely related to malakoplakia, with the absence of the characteristic Michaelis-Gutmann bodies.  This entity most frequently results from a chronic, ascending, bacterial urinary tract infection, most frequently due to E. coli or other gram-negative bacteria.