Blastomycosis : Diagnosis, Treatment, And Pathopysiology
- North American blastomycosis is a systemic fungal infection caused by Blastomyces dermatitidis.
- Pulmonary disease probably occurs by inhalation conidia, which convert to the yeast forms in the lungs. It may be acute or chronic and can mimic infection with tuberculosis, pyogenic bacteria, other fungi, or malignancy.
- Blastomycosis can disseminate to virtually every other body organ including skin, bones and joints, or the genitourinary tract without any evidence of pulmonary disease.
Clinical Presentation :
- Acute pulmonary blastomycosis is generally an asymptomatic or self-limited disease characterized by fever, shaking chills, and a productive, purulent cough.
- Pulmonary blastomycosis may present as a more chronic or subacute disease, with low-grade fever, night sweats, weight loss, and a productive cough resembling that of tuberculosis rather than bacterial pneumonia.
- Chronic pulmonary blastomycosis is characterized by fever, malaise, weight loss, night sweats, and cough.
Diagnosis of Blastomycosis :
- The simplest and most successful method of diagnosing blastomycosis is by direct microscopic visualization of the large, multinucleated yeast with single, broad-based buds in sputum or other respiratory specimens, following digestion of cells and debris with 10% potassium hydroxide.
- Histopathologic examination of tissue biopsies and culture of secretions should be used to identify B. dermatitidis.
Treatment of Blastomycosis :
- In patients with mild pulmonary blastomycosis, the clinical presentation of the patient, the immune competence of the patient, and the toxicity of the antifungal agents are the main determinants of whether or not to administer antifungal therapy. All immunocompromised patients and patients with progressive disease or with extrapulmonary disease should be treated.
- Some authors recommend ketoconazole therapy for the treatment of self-limited pulmonary disease, with the hope of preventing late extrapulmonary disease.
- Itraconazole, 200 to 400 mg/day, is an effective as a first-line agent in the treatment of non-life-threatening non-CNS blastomycosis.
- All patients with disseminated blastomycosis and those with extrapulmonary disease require therapy (ketoconazole, 400 mg/day orally for 6 months). CNS disease should be treated with amphotericin B for a total cumulative dose greater than 1 g.
- Patients who fail or are unable to tolerate itraconazole therapy, or who develop CNS disease, should be treated with amphotericin B for a total cumulative dose of 1.5 to 2.5 g.
- HIV-infected patients should receive induction therapy with amphotericin B and chronic suppressive therapy with an oral azole antifungal. Itraconazole is the drug of choice for non-life-threatening histoplasmosis.