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Key Points

  • Blastomyces dermatitidis
    • Characteristics
      • Dimorphic fungus
        • mold in soil
          • Have multicellular hyphae
        • yeast inside body (at body temperatures)
          • No hyphae seen in biopsy specimens
    • Transmission
      • Endemic areas
        • Great Lakes Region
        • Mississippi and Ohio River Basin
      • Inhalation of spores (MB)
      • Cannot be transmitted from person to person (unlike TB)
    • Presentation
      • Causes Blastomycosis
        • Pneumonia
          • Fever, cough, shortness of breath
          • CXR: alveolar infiltrates, although reticulonodular patterns may be seen
          • Chronically with cavitations, fibronodular lesions (like TB)
        • Skin lesions
          • most common extrapulmonary site
          • presents as papular or pustular vegetative (verrucous) lesions in exposed areas
        • Osteomyelitis may be seen
          • After skin, bone is next most common extrapulmonary site
    • Diagnosis
      • Histopathology
        • Broad-based budding yeast
          • Same size as RBCs
        • Can form granulomas (like TB)
      • Fungal sputum culture, serum antigen, PCR are also used
        • Must mention Blastomyces; therefore low-yield
    • Treatment
      • Itraconazole for local infection
        • Fluconazole or ketoconazole may be used as a substitute, but less effective than itraconazole
      • Amphotericin B for systemic infection