Clinical Manifestations and Treatment of Blastomycosis

Abstract

The causal agents of blastomycosis, Blastomyces dermatitidis and Blastomyces gilchristii, belong to a group of thermally dimorphic fungi that can infect healthy and immunocompromised individuals. Following inhalation of mycelial fragments and spores into the lungs, Blastomyces spp convert into pathogenic yeast and evade host immune defenses to cause pneumonia and disseminated disease. The clinical spectrum of pulmonary blastomycosis is diverse. The diagnosis of blastomycosis requires a high degree of clinical suspicion and involves culture-based and non-culture-based fungal diagnostic tests. The site and severity of infection, and the presence of underlying immunosuppression or pregnancy, influence the selection of antifungal therapy.

Keywords: Acute respiratory distress syndrome; Blastomycosis; Dimorphic fungi; Pneumonia.

Figure 1. Blastomyces dermatitidis yeast

Broad-based budding yeast at 37°C. Arrow points to the broad-based bud between mother and daughter cell. Scale bar is 10 μm.

Figure 2. Map of the distribution of endemic and epidemic blastomycosis in North America

Cross-hatching denotes geographic distribution of cases. Circled numbers denote location of epidemics referred to in Table 1.

Figure 3. Miliary blastomycosis and acute respiratory distress syndrome

Chest radiographs demonstrating miliary blastomycosis that progressed to diffuse, dense consolidation in a patient with acute respiratory distress syndrome (ARDS).

Figure 4. Cavitary blastomycosis

Chest radiograph (A) and corresponding chest computed tomography image (B) of a patient with multiple cavities and consolidation in the right upper lung at the time of initial clinical presentation. (C) Chest radiograph after completion of antifungal therapy demonstrates residual scarring and bronchiectasis.

Figure 4. Cavitary blastomycosis

Chest radiograph (A) and corresponding chest computed tomography image (B) of a patient with multiple cavities and consolidation in the right upper lung at the time of initial clinical presentation. (C) Chest radiograph after completion of antifungal therapy demonstrates residual scarring and bronchiectasis.

Figure 4. Cavitary blastomycosis

Chest radiograph (A) and corresponding chest computed tomography image (B) of a patient with multiple cavities and consolidation in the right upper lung at the time of initial clinical presentation. (C) Chest radiograph after completion of antifungal therapy demonstrates residual scarring and bronchiectasis.

Figure 5. Cutaneous ulcer

Cutaneous ulcer due to blastomycosis in a patient who received TNF-α inhibitor therapy.