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SOURCE

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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. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146073167. Accessed March 14, 2017.

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DEFINITION

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  • Systemic fungal infection.

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ETIOLOGY

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  • Systemic fungal infection caused by Blastomyces dermatitidis

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PATHOPHYSIOLOGY

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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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EPIDEMIOLOGY

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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 southeastern, south central, and midwestern United States as well as Canadian provinces that border the Great Lakes.

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RISK FACTORS

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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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CLINICAL PRESENTATION

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SIGNS AND SYMPTOMS
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  • Colonization does not occur.

  • Can disseminate to virtually every other body organ, including skin, bones, and joints, or the genitourinary tract, without evidence of pulmonary disease.

  • 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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DIAGNOSIS

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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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DESIRED OUTCOMES

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  • Resolution of clinical abnormalities.

  • Prevention of relapse.

  • Eradication of ...

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