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malakoplakia
Etiology:
- occurs in immunocompromised patients
- rarely in patients with HIV1 infection due to preserved monocytic antimicrobial function
- infection most commonly due to Escherichia coli
- Staphylococcus aureus, Pseudomonas aeruginosa, & Rhodococcus equi less common
Epidemiology:
- rare, < 500 cases
- age range broad, median age at presentation is 53 years
Pathology:
- presentation as friable yellow soft plaques
- inadequate killing of bacteria by macrophages or monocytes with defective phagolysosomal activity
- partially digested bacteria accumulate in monocytes or macrophages & lead to the deposition of calcium & iron on residual bacterial glycolipid
- result is basophilic inclusion structure, Michaelis-Gutmann body, pathognomonic for malakoplakia
- sheets of ovoid histiocytes with fine eosinophilic cytoplasmic granules (von Hansemann cells) seen on microscopy
Clinical manifestations:
- most frequently affects genitourinary system
- can present as renal failure or pyelonephritis-like syndrome
- may involve other others including bone, lung, skin
- cutaneous manifestations
- erythematous papules, subcutaneous nodules, draining abscesses, cutaneous ulcers, nonhealing surgical wounds, or draining fistulas
Laboratory:
- culture of draining sinuses
- bacterial culture for aerobic & anaerobic bacteria
- mycobacterial culture
- fungal culture
Special laboratory:
- skin biopsy
- fine needle aspiration or tissue biopsy as indicated
- electron microscopy may show Michaelis-Gutmann bodies (lysosomes filled with partially digested bacteria)
Management:
- treatment with antibiotics that concentrate in macrophages (quinolones, trimethoprim-sulfamethoxazole) is associated with a high cure rate
- discontinuation of immunosuppressive therapy
- excision & drainage of subcutaneous abscesses
General
granulomatous disease
infection (infectious disease)
References
- Elbendary AM, James WD
Medscape: Malakoplakia
https://emedicine.medscape.com/article/1055606-overview