8 October 2008 – Case of the Week #131
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We thank Dr. Daniel Ostler, MD Anderson Cancer Center, Houston, Texas (USA) for contributing this case. To contribute a Case of the Week, email NatPernick@Hotmail.com with the clinical history, your diagnosis and diagnostic microscopic images in JPG, GIF or TIFF format (send as attachments, we will shrink if necessary). Please include any other images (gross, immunostains, etc.) that may be helpful or interesting. We will write the discussion (unless you want to), list you as the contributor, and send you $35 (US dollars) by check or PayPal for your time after we send out the case. Please only send cases with high quality images and a diagnosis that is somewhat unusual (or a case with unusual features).
Case of the Week #131
A 76 year old woman had a bladder biopsy for hematuria.
What is your diagnosis?
Malakoplakia is a rare chronic granulomatous condition that can affect any organ, although it commonly affects the urinary tract, particularly the bladder (Radiographics 2006;26:1847). It is caused by defects in phagocytic or degradative functions of histiocytes in response to gram negative coliforms (E. coli or Proteus), and is more common in the immunocompromised (HIV, renal transplant recipients) and in women.
Grossly, it presents as multiple, 3-4 mm soft, yellow plaques or nodular thickenings near the trigone that resemble carcinoma. Microscopically, it consists of foamy epithelioid histiocytes with PAS+ granular eosinophilic cytoplasm in the lamina propria, accompanied by lymphocytes and occasional giant cells. The histiocytes have an increased number of phagosomes containing non-digested bacteria (usually E coli or Proteus). The histiocytes also contain Michaelis-Gutmann bodies (image), which are iron containing, cytoplasmic, laminated mineralized concretions (von Kossa stain for calcium, iron stain).
Treatment includes antibiotics that concentrate in macrophages, such as quinolone or trimethoprim-sulfamethoxazole, or antibiotics directed against E. coli plus surgery. Another possible treatment is bethanechol, which may correct the decreased cGMP levels that may interfere with complete bacterial killing (eMedicine).
Nat Pernick, M.D., President
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