Microscopic description:

Marked histiocytic proliferation, chronic inflammation

Abundant Michaelis-Gutmann bodies (iron containing, cytoplasmic laminated mineralized concretions)

IHC: AE1/3 stains reactive urothelium, positive Prussian blue and CD68.

Discussion:

First described by Michaelis and Gutmann in 1902 and later named by Von Hansseman

More common in immunocompromised (HIV, renal transplant recipients) and women

Single or multiple white-yellow soft raised plaques on the mucosal surface

Often misdiagnosed clinically as a malignant condition

Caused by defects in phagocytic or degradative functions of histiocytes in response to gram negative coliforms (E. coli or Proteus) that results in chronic inflammatory state, followed by intracellular deposition of iron and calcium (known as Michaelis-Gutmann bodies)

Can be divided in 3 stages:

  • Initial inflammatory stage
  • Classic stage with abundant Michaelis-Gutmann bodies
  • Third stage with progressive fibrous tissue and scarring

Foamy epithelioid histiocytes with PAS+ granular eosinophilic cytoplasm in lamina propria, some lymphocytes and occasional giant cells

Histiocytes have increased number of phagosomes containing non-digested bacteria (usually E. coli or Proteus), contain Michaelis-Gutmann bodies (iron containing, cytoplasmic laminated mineralized concretions)

References:

Wong-You-Cheong JJ, Woodward PJ, Manning MA, Davis CJ. From the archives of the AFIP: Inflammatory and nonneoplastic bladder masses: radiologic-pathologic correlation. Radiographics. 2006 Nov-Dec;26(6):1847-68. doi: 10.1148/rg.266065126. PMID: 17102055.

O'Sullivan O, Clyne O, Drumm J. Encrusted cystitis--an unusual cause of recurrent frank haematuria. Ir J Med Sci. 2006 Oct-Dec;175(4):74-5. doi: 10.1007/BF03167973. PMID: 17312835.

Bylund J, Pais VM Jr. A case of acute renal failure caused by bilateral, multifocal malacoplakia lesions of the bladder and ureters. Nat Clin Pract Urol. 2008 Sep;5(9):516-9. doi: 10.1038/ncpuro1173. PMID: 18679396.

Patnayak R, Reddy MK, Subramanian S, Jena A, Ravisankar G, Dandu RS. An unusual case of bilateral hydroureteronephrosis caused by uretero-vesico malakoplakia in a young male: a case report and review of the literature. Cases J. 2009 May 29;2:7527. doi: 10.1186/1757-1626-2-7527. PMID: 19829997; PMCID: PMC2740110.

CASE IMAGES