Answer: Fatal Pulmonary Blastomyces dermatitidis Infection. Blastomyces dermatitidis is a dimorphic fungus, endemic in the United States in the Ohio and Mississippi River valleys (1). Blastomyces most commonly causes asymptomatic pulmonary infection. However, infection may progress to acute respiratory distress syndrome (ARDS). Systemic infection may also occur, especially in immunocompromised patients.
The diagnosis of pulmonary blastomycosis is often delayed because of failure to consider blastomycosis in patients presenting with community-acquired pneumonia (2–4). In Mississippi, only 5% of patients were diagnosed at initial presentation, and a delay in diagnosis of more than 1 month was reported for 43% of the patients (4). Over 60% of patients who died of blastomycosis-associated ARDS were not suspected of having a fungal infection until late in their infectious course (5). The fatality rates for ARDS and non-ARDS patients were 89% and 10%, respectively (6, 7). Presumably, early diagnosis and directed treatment would prevent complications such as ARDS and improve outcome.
Complicating the diagnosis, Blastomyces may take several weeks to grow in culture. Therefore, rapid direct-detection methods, such as Gram and KOH-calcofluor white staining on respiratory samples and urinary antigen testing, are crucial for early diagnosis. In respiratory and tissue specimens, Blastomyces fungi may be recognized by their large yeast forms (8 to 15 μm in diameter) with characteristic thick “double-contoured” cell walls and broad-based budding (see Fig. 1 in the photo quiz). For this patient, the results for the Blastomyces antigen test on serum and urine samples were also positive, at 10.47 ng/ml and >14.7 ng/ml, respectively (reference range, none detected), as was the result for the highly cross-reactive Histoplasma urinary antigen test (6.0 ng/ml; reference range, <0.5 ng/ml). However, the result for a (1-3)-β-glucan test on the serum sample was negative, another characteristic finding (8).
Taken together, these results show a progressive case of blastomycosis complicated by ARDS and lack of recognition until late in the course of disease. Both special microbiological stains and antigen testing led to a definitive diagnosis.
(See page 825 in this issue [doi:10.1128/JCM.00851-14] for photo quiz case presentation.)
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