Blastomycosis

Introduction

• 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 (TB), 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 and Diagnosis

• Acute pulmonary blastomycosis is generally an asymptomatic or self-limited disease characterized by fever, shaking chills, and a productive, purulent cough, with or without hemoptysis in immunocompetent individuals.
• Sporadic 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 TB rather than bacterial pneumonia. Chronic pulmonary blastomycosis is characterized by fever, malaise, weight loss, night sweats, chest pain, and productive cough.
• 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

• In the immunocompetent host, acute pulmonary blastomycosis can be mild and self-limited and may not require treatment. However, consideration should be given to treating all infected individuals to prevent extrapulmonary dissemination. All individuals with moderate to severe pneumonia, disseminated infection, or those who are immunocompromised require antifungal therapy.
• Itraconazole, 200 to 400 mg/day, demonstrated 90% efficacy as a first-line agent in the treatment of non-life-threatening, non-CNS blastomycosis and 95% success rate for compliant patients who completed at least 2 months of therapy.