Case 237 - Discussion

Uploaded: 2008-05-29, Updated: 2008-05-30

Malakoplakia

The Key Features

  • Most commonly bladder, then ureter and kidney, rarely skin;

  • Pathogenesis: Defective macrophage killing of bacteria;

  • Michaelis-Gutmann bodies: basophilic intracellular inclusions, 5-15 um, concentric laminations;

  • von Kossa stain for calcium and Perls Prussian blue stain for iron.

CLINICAL FEATURES

  • An inflammatory condition usually affects the genitourinary tract, most commonly in immunocompromised patients;

  • Location: most commonly bladder, then ureter and kidney, rarely skin;

  • Female predominant, 80%;

  • Pathogenesis: Defective macrophage killing of bacteria results in an accumulation of bacterial degradation products and a granulomatous reaction, which clinically manifests as the formation of a papule, a plaque, or an ulceration. E coli is the most common gram-negative bacteria, but Staphylococcus aureus and Pseudomonas aeruginosa may be cultured. Partially digested bacteria accumulate in monocytes or macrophages and lead to the deposition of calcium and iron on residual bacterial glycolipid. The presence of the resulting basophilic inclusion structure, the Michaelis-Gutmann body, is considered pathognomonic for malakoplakia;

  • Incidence: < 500 in US annually, most patients have genitourinary tract disease.

GROSS FINDINGS

  • A papule, a plaque, or an ulceration that is yellow to pink;

MICROSCOPIC FINDINGS

  • Sheets of ovoid histiocytes with fine eosinophilic cytoplasmic granules (von Hansemann cells);

  • Michaelis-Gutmann bodies: basophilic intracellular inclusions, 5-15 um, concentric laminations.

DIFFERENTIAL DIAGNOSES

 

IMMUNOHISTOCHEMISTRY AND SPECIAL STAINS

  • PAS+,diastase resistant;

  • von Kossa stain for calcium;

  • Perls Prussian blue stain for iron;

  • Gram stain may demonstrate gram-negative bacteria;

  • Immunohistochemical studies demonstrate positive results for CD68 antibodies, lysosomes, and a-chymotrypsin.

ELECTRON MICROSCOPIC FINDINGS

  • Michaelis-Gutmann bodies consist of lysosomes filled with partially digested bacteria.

TREATMENT AND PROGNOSIS

  • Treat underlying disease and surgical resection of the lesion.

REFERENCES

  • http://www.emedicine.com/derm/topic872.htm