Updated: 6/12/2019

Systemic Mycoses

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Snapshot
  • A 38-year-old man presents to an urgent care clinic in Ohio for a 3-week cough. He reports having fevers, chills, and fatigue. He recently went on a local hiking trip that included waterfalls, freshwater lakes, and caves. He reports his cough was worse in the beginning but has lingered. He denies any rashes, vomiting, or diarrhea. A chest radiograph shows patchy pulmonary infiltrates and hilar lymphadenopathy. A sputum sample under microscopy shows macrophages with intracellular yeast cells. (Histoplasmosis)
Introduction
  • Introduction
    • dimorphic yeasts
      • mold form in the soil, outside the body
        • grows on Sabouraud agar
      • yeast form in tissues, inside the body
        • grows on blood agar
      • Coccidioides immitis is an exception
        • spherule form, not yeast, in tissue
    • demographics
      • depends on geographic location 
    • transmission
      • inhalation of spores
      • cannot be transmitted between people
    • pathogenesis
      • inhalation causes a pulmonary infection
      • fungi can then disseminate to other organs, particularly the skin
      • causes granulomas
        • composed of epithelioid cells and multinucleated giant cells
        • Th1 mediated
    • clinical syndromes
      • pneumonia
      • chronic inflammatory lung disease
      • systemic dissemination
Overview of Systemic Mycoses
Clinical Syndrome Histoplasmosis
Coccidioidomycosis
Blastomycosis Paracoccidioidomycosis
Organism
  • Histoplasma capsulatum
  • Coccidioides immitis
  • Coccidioides posadasii
  • Blastomyces dermatitidis
  • Paracoccidioides brasiliensis
  • Paracoccidioides lutzii
Demographics
  • Mississippi
  • Ohio River Valley
  • Southwestern US
  • California
  • Eastern US
  • Central US
  • Latin America
Skin manifestations
  • Ulcers on oral mucosa
  • Erythema nodosum
  • Erythema multiforme
  • Verrucous skin lesions
  • Verrucous skin lesions
Histology
  • Macrophages filled with fungus cells
  • Spherules (larger than red blood cells (RBCs)) filled with endospores
  • Broad-based budding yeast (same size as RBCs)
  • Budding yeast larger than RBCs
 
  • Differential
    • tuberculosis
      • also affects the pulmonary system
      • causes granulomas, cavitations, and calcifications
      • unlike these systemic mycoses, tuberculosis can be transmitted person to person
  • Treatment
    • amphotericin B
      • systemic infections
    • itraconazole or fluconazole  
      • localized infections
Histoplasmosis
  • Histoplasma capsulatum
    • demographics
      • Mississippi
      • Ohio River Valley (Ohio and Tennessee)
    • risk factors
      • bird or bat excretions
      • chicken farms
      • exploring caves or spelunking 
      • HIV infection
  • Presentation
    • pneumonia
      • usually self-limiting
    • chronic cavitary lung disease
    • hilar lymphadenopathy
    • gastrointestinal symptoms
    • splenomegaly
    • oral mucosal ulcers on tongue or palate
  • Imaging
    • chest radiograph
      • normal or with patchy infiltrates with hilar/mediastinal lymphadenopathy
  • Studies
    • detection of antigen in serum or urine
    • tissue biopsy
      • methenamine silver or periodic acid-Schiff stains show oval yeasts within macrophages 
Coccidioidomycosis
  • Coccidioides immitis or Coccidioides posadasii
    • demographics
      • southwestern US
        • Arizona, New Mexico, and southern California
      • Central and South America
    • risk factors
      • earthquakes releases spherules from soil
  • Presentation 
    • pneumonia
    • dissemination to skin in 50% of patients
      • erythema nodosum
        • “desert bumps”
      • erythema multiforme
    • arthralgias
      • “desert rheumatism”
    • meningitis
  • Imaging
    • chest radiograph
      • consolidations, hilar/mediastinal lymphadenopathy, or pleural effusions
    • chest computed tomography (CT)
      • multifocal ground glass opacities
  • Studies
    • detection of immunoglobulin M (IgM) in serum
    • detection of antigen in serum
    • tissue biopsy
      • spherules (larger than RBCs) filled with endospores 
Blastomycosis
  • Blastomyces dermatitidis
    • demographics 
      • eastern US
      • central US
    • risk factors
      • HIV infection
  • Presentation
    • majority are asymptomatic
    • pneumonia
    • severe chronic inflammatory lung disease
    • dissemination to skin, often on the face
      • verrucous skin lesions
      • granulomatous nodules
      • ulcers
  • Imaging
    • chest CT
      • infiltrates without hilar lymphadenopathy
      • cavitary lesions in chronic disease
  • Studies
    • tissue biopsy
      • fungal stain shows broad-based budding yeast
      • same size as red blood cells (RBCs)
Paracoccidioidomycosis
  • Paracoccidioides brasiliensis or Paracoccidioides lutzii
    • also known as “South American blastomycosis”
    • demographics
      • Latin America
      • male > female
    • risk factors
      • contact with soil
  • Presentation 
    • severe chronic inflammatory lung disease
    • pneumonia
    • lymphadenopathy
    • dissemination to skin, often on the face but can also affect mucous membranes
      • verrucous skin lesions
      • granulomatous nodules
  • Imaging
    • chest radiograph
      • bilateral iniltrates without cavitation
  • Studies
    • tissue biopsy
      • budding yeast
      • "captain’s wheel” formation
      • granulomas
Other Systemic Mycoses
  • Sporothrix schenckii
    • typically a localized infection but can present systemically
      • localized disease can present with painful nodules traveling along lymphatic channels 

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