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Source: Carver PL. Invasive Fungal Infections. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. http://accesspharmacy.com/content.aspx?aid=8005562. Accessed June 24, 2012.

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  • Systemic fungal infection

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  • Systemic fungal infection caused by Blastomyces dermatitidis

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  • Pulmonary infection probably occurs by inhalation of conidia, which convert to yeast form in lung.
  • Inflammatory response, followed by cell-mediated immunity and formation of noncaseating granulomas

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  • B. dermatitidis considered to be soil inhabitant, though attempts to isolate it in nature have frequently been unsuccessful.
  • Has been found in soil containing decayed vegetation, decomposed wood, and pigeon manure.
  • Found in south central and midwestern United States and Canada.

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  • No sex, age, or occupational predilection
  • Review of sporadic cases suggests that people with outdoor occupations that expose them to soil at highest risk.

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Signs and Symptoms

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  • Can disseminate to virtually every other body organ, including skin, bones, and joints, or the genitourinary tract, without evidence of pulmonary disease.
  • Colonization does not occur.
  • Acute pulmonary blastomycosis
    • Generally asymptomatic or self-limited disease
    • Characterized by fever, shaking chills, and productive, purulent cough, with or without hemoptysis in immunocompetent individuals
    • Difficult to differentiate from other respiratory infections based on symptoms
  • Sporadic pulmonary blastomycosis
    • More chronic or subacute disease
    • Characterized by low-grade fever, night sweats, weight loss, and productive cough resembling that of TB rather than bacterial pneumonia
  • Chronic pulmonary blastomycosis
    • Characterized by fever, malaise, weight loss, night sweats, chest pain, and productive cough
    • Evidence of disseminated disease can appear 1–3 years after resolution of primary pneumonia.
      • 40% of patients with disseminated disease do not have reactivation of pulmonary disease.
      • Most common sites include skin and bony skeleton.
        • Male urogenital tract may also be involved.

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Means of Confirmation and Diagnosis

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  • Direct microscopic visualization of large, multinucleated yeast with single, broad-based buds in sputum or other respiratory specimens, following digestion of cells and debris with 10% potassium hydroxide
  • No reliable skin test available

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Laboratory Tests

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  • Culture secretions: Up to 30 days required to isolate and identify small inoculum.
  • Complete blood count (CBC): Leukocytosis and anemia may be present.

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Imaging

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  • Chest radiograph
  • CT scan

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Diagnostic Procedures

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  • Histopathologic examination of tissue biopsies and culture of secretions

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Differential Diagnosis

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  • Tuberculosis
  • Bacterial pneumonia
  • Malignancy
  • Other fungal infection

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  • Resolution of clinical abnormalities
  • Prevention of relapse
  • Eradication of infection

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  • Mild pulmonary blastomycosis
    • Use of antifungal therapy based on:
      • Clinical presentation and immunocompetency of patient
      • Toxicity of antifungal agents
  • All immunocompromised patients and patients with progressive or extrapulmonary disease should be treated (Table 1).
    • Blastomycosis uncommon opportunistic disease in immunocompromised patients, including those with AIDS.
      • Late and frequently fatal complication when occurs.

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