Clinical Features of Cutaneous Microsporidiosis
Cutaneous microsporidiosis presents primarily as recurrent subcutaneous nodules with associated superficial and deep lymphocytic and granulomatous dermatitis, often with focal necrosis. 1
Overview of Microsporidiosis
Microsporidia are obligate intracellular parasites that have been reclassified from protozoa to fungi. They are characterized by small, highly resistant spores typically 1-10 μm in size 2. Human microsporidiosis is an emerging opportunistic infection that primarily affects immunocompromised individuals, including:
- HIV/AIDS patients
- Organ transplant recipients
- Patients on immunosuppressive medications
- Children
- Elderly individuals 3
Key Cutaneous Manifestations
The cutaneous manifestations of microsporidiosis include:
- Recurrent subcutaneous nodules 1
- Granulomatous dermatitis with focal necrosis 1
- Oval 1-3 μm spores visible within necrotic areas on tissue staining 1
Systemic Features Often Associated with Cutaneous Disease
Patients with cutaneous microsporidiosis frequently present with concurrent systemic manifestations:
- Intermittent diarrhea (most common systemic symptom) 1, 4
- Chronic sinusitis 1
- Possible disseminated disease in severely immunocompromised hosts 4
Diagnostic Findings
Histopathologic examination reveals:
- Superficial and deep lymphocytic infiltrates 1
- Granulomatous inflammation 1
- Focal areas of necrosis containing oval spores 1
- Spores measuring 1-3 μm that can be visualized with special stains 1
Risk Factors
The primary risk factors for developing cutaneous microsporidiosis include:
- Immunosuppression (particularly HIV with CD4 counts <100 cells/mm³) 4
- Use of immunosuppressive medications (e.g., mycophenolate mofetil) 1
- Chronic inflammatory conditions requiring immunosuppression 1
Differential Diagnosis
Cutaneous microsporidiosis should be differentiated from other causes of nodular skin lesions in immunocompromised patients, including:
- Fungal infections (particularly deep fungal infections)
- Mycobacterial infections
- Other parasitic infections
- Cutaneous manifestations of lymphoma 5
Common Pitfalls in Diagnosis
- Failure to consider microsporidiosis in immunocompromised patients with unexplained skin nodules
- Inadequate tissue sampling or improper staining techniques
- Misidentification of the small spores as other microorganisms
- Failure to correlate skin findings with systemic symptoms 1, 6
Species Commonly Associated with Human Infection
While 14 species of microsporidia are known to infect humans, the most common species causing human infections are:
- Enterocytozoon bieneusi (primarily intestinal disease)
- Encephalitozoon intestinalis (intestinal and disseminated disease)
- Other species can cause cutaneous manifestations in the appropriate clinical context 3, 6
Cutaneous microsporidiosis remains a rare but important diagnosis to consider in immunocompromised patients presenting with unexplained nodular skin lesions, particularly when accompanied by gastrointestinal symptoms or other systemic manifestations.