questions 6

Systemic Mycoses

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Topic updated on 01/05/17 3:10pm

Introduction
  • Systemic mycoses consist of 4 dieases
    • Histoplasmosis (Histoplasma capsulatum)
    • Coccidiomycosis (Coccidioides immitis)
    • Blastomycosis (Blastomyces dermatitidis)
    • Paracoccidioidomycosis (Paracoccidioides brasiliensis)
  • Characteristics of systemic mycoses
    • dimorphic
      • mold in soil ("mold in the cold" - 25 deg C)
        • grown on Sabouraud's agar
      • yeast in tissue (37 deg C)
        • grown on blood agar
      • Coccidioides immitis is an exception
        • spherule (not yeast) in tissue
    • endemic to a specific area
  • Pathogenesis
    • fungi inhaled in spore
    • lungs are locally infected
    • infection disseminates hematogenously
Histoplasma capsulatum
  • Diseases
    • histoplasmosis (pneumonia)
      • hilar lymphadenopathy
      • ulcerated tongue lesions
  • Pathogenesis
    • invades macrophages 
      • oval yeast cells seen within macrophages
      • the only systemic fungus with yeast phagocytosed by macrophages
  • Transmission
    • cave exploring/spelunking  
    • endemic to Mississippi and Ohio River Valleys
      • Ohio and Tennessee
    • found in bird and bat droppings (chicken farms)
  • Laboratory
    • NOT encapsulated despite name
Coccidioides immitis
  • Diseases
    • coccidioidomycosis 
      • mild pneumonia
        • opportunistic infection in AIDS patients in Arizona
      • meningitis
      • disseminated disease to skin and bone in immunocompromised
  • Transmission
    • endemic to southwest U.S.
      • AZ, NM, southern CA, and San Joaquin Valley
    • incidence ↑ after earthquakes
      • spherules released from soil
  • Laboratory
    • spherule (not yeast) in tissue
      • spherules contain endospores seen on biopsy 
Blastomyces dermatitidis
  • Diseases
    • blastomycosis (most severe disease of the group)
      • chronic inflammatory lung disease
      • granulomatous nodules
      • dissemination to skin and bone
    • rarest of the group
  • Transmission
    • endemic to Mississippi River Valley and Central America
    • found in soil and rotting wood
  • Laboratory
    • round, broad-based budding yeast
      • thick, double refractive walls
Paracoccidioides brasiliensis 
  • Diseases
    • paracoccidioidomycosis (pneumonia) 
  • Transmission
    • endemic to Latin America
  • Laboratory
    • "captain's wheel" appearance
    • budding yeast
Presentation (Systemic mycoses)
  • 3 presentations
    • asymptomatic
      • majority of cases
      • most people never visit the doctor
    • pneumonia
      • fever
      • cough
      • may be acute or chronic
      • clinical presentation is similar to TB
    • disseminated disease
      • fever, malaise
      • meningitis, bone lytic and skin granulomas
      • seen in immunocompromised
Evaluation (Systemic mycoses)
  • Radiographs
    • CXR will show lesion
  • Biopsy
    • stained with silver stain directly or KOH prep
    • cultured on Sabouraud's or blood agar
  • Delayed hypersensitivity reaction
    • can be used to show previous exposure (similar to PPD)
      • coccidioidin
      • histoplasmin
Differential (Systemic mycoses)
  • Tuberculosis
    • similarities with TB
      • inhaled lung infection
      • wide range of severity (asymptomatic to chronic)
      • granulomas, cavitations, and calcifications
      • hematogenous dissemination
      • show previous exposure with PPD-like hypersensitivity reaction
      • however, these infections do NOT transmit from person-to-person, unlike TB
Treatment (Systemic mycoses)
  • Fluconazole or ketoconazole
    • indications
      • local infection
  • Amphotericin B
    • indications
      • systemic infection


  RATE CONTENT
5.0
AVERAGE 5.0 of 5 RATINGS

Qbank (2 Questions)

TAG
(M1.MC.12) A 43-year-old man presents to the emergency department with cough and fever. On a sputum sample he is found to have spherules containing endospores, as shown in Figure A. How is he most likely to have contracted his disease? Topic Review Topic
FIGURES: A          

1. Hunting in the woods of Connecticut
2. Swimming in a freshwater pond in Louisiana
3. Hiking in the deserts of Arizona
4. Walking in caves in the Mississippi River Valley
5. Cleaning out pigeon coops in Ohio

PREFERRED RESPONSE ▶
TAG
(M1.MC.14) A 59-year-old man with no significant past medical history presents to the emergency room with the ulcerative skin lesion shown in Figure A. He had a bad pneumonia several weeks ago. His vital signs are stable, and the remainder of his physical examination is benign. The lesion is swabbed and cultured revealing the organism shown in Figure B. Which of the following is most likely true regarding this disease? Topic Review Topic
FIGURES: A   B        

1. The patient received the illness from bat droppings and may be treated with PO itraconazole
2. The patient received the illness in the Southwest and may be treated with PO fluconazole or itraconazole
3. The patient received the illness in the Mississippi River Valley and may be treated with PO itraconazole
4. The patient received the illness in Latin America and the organism may form a captain's wheel formation
5. The patient received the illness from plant material and may be treated with potassium iodide

PREFERRED RESPONSE ▶
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