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Pathology of Cutaneous Malakoplakia 

Dr Sampurna Roy MD

 

Dermatopathology Quiz Case 70

Diagnosis: Cutaneous Malakoplakia

 

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Malakoplakia (from the Greek malacos, soft, and placos, plaques) is a rare granulomatous disease that occurs commonly in the urinary tract.

It was first described by Michaelis and Gutmann in 1902.

Other organs like the genito-urinary tract, testis, epididymis, lymph nodes, nasopharynx , tonsil and retroperitoneal tissue have been also involved though less frequently.  Rare cases of Malakoplakia have been reported in the middle ear.

Pathogenesis: 

1) Microorganisms might play a role in the pathogenesis. The organisms include Escherichia coli (found in more than two thirds of cases), Mycobacterium tuberculosis, Proteus, and Staphylococcus aureus.

Specific bacteria are found in certain categories of patients, for example, coliform bacteria in patients with chemotherapy and Rhodococcus equi in patients with acquired immunodeficiency syndrome.

2) An abnormal or altered immune response has been also implicated in the pathogenesis.

3) The third hypothesis is an abnormal macrophage response because of defective lysosomal function.

It is suggested that macrophages in malakoplakia are capable of phagocytosis but unable to digest the bacteria.

Partially digested bacteria accumulate in monocytes or macrophages and lead to the deposition of calcium and iron on residual bacterial glycolipid.

Gross features:

Grossly, malakoplakia can present as soft tan yellow plaques and nodules or even extensive bands.

The lesion is usually solitary but can be multiple.

Microscopic features:

Histologically, it is defined by sheets of histiocytes called von Hansemann histiocytes or Hansemann cells  with accumulation of granular basophilic periodic acid-Schiff - positive, diastase-resistant inclusions and calcified Michaelis-Gutmann bodies, which are pathognomonic but not necessary for diagnosis. 

The composition of Michaelis-Gutmann bodies has been shown to be 94.6% organic and 5.4% inorganic, with the inorganic components being calcium, phosphorus, and iron.

 

Further reading:

Malakoplakia outside the urinary tract

Malakoplakia of the middle ear

Malakoplakia of the middle ear.

Malakoplakia of the temporal bone in a nine-month-old infant

Scabies: 10 facts about Pathology of Scabies Infestation

 

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Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


 

 

 

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