Clinical Manifestations and Treatment of Blastomycosis

Abstract

Synopsis The etiologic agents of blastomycosis, Blastomyces dermatitidis and B. 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, which facilitates evasion of host immune defenses to cause pneumonia and disseminated disease. The clinical spectrum of pulmonary blastomycosis is diverse, ranging from subclinical infection, acute pneumonia resembling bacterial community-acquired pneumonia, chronic pneumonia mimicking tuberculosis or malignancy, and acute respiratory distress syndrome. The diagnosis of blastomycosis requires a high-degree of clinical suspicion and involves the use of culture and non-culture-based fungal diagnostic tests. The site and severity of infection, and the presence of underlying immunosuppression or pregnancy influence selection of antifungal therapy.

Notes from the Field:Blastomycosis Cases Occurring Outside of Regions with Known Endemicity — New York, 2007–2017

“…Blastomycosis is treated with antifungal medications, typically itraconazole or another azole for mild or moderate disease and lipid formulations of amphotericin B for severe disease. Delays in diagnosis of more than 1 month have been observed in >40% of patients ( 3 ), suggesting that a diagnosis of blastomycosis is often not considered until after other treatments have failed. Blastomycosis diagnosis can be confirmed by fungal culture, with the optimal specimen source depending on the type of infection.…”

Pleural Effusion in Pulmonary and Extrapulmonary Blastomycosis

“…But in fact, the primary infection is caused by inhalation of Blastomyces and the prime target organ is the lung. Blastomyces dermatitidis commonly infects the lung through inhalation of conidia, and then disseminates to extrapulmonary sites including the skin, bones, and the genitourinary organs [17]. Therefore, it would be more reasonable to consider blastomycosis similar to tuberculosis, histoplasmosis, or cryptococcosis in that the disease is primarily a disease of the lungs and that all other manifestations stem from pulmonary involvement.…”

Endemic Mycoses and Cryptococcus in Solid Organ Transplant Recipients

“…The clinical manifestations of blastomycosis can vary widely, ranging from an asymptomatic infection to pulmonary disease progressing to acute respiratory distress syndrome (ARDS). Symptom onset after inhalation of conidia ranges between 3 weeks to 3.5 months [52]. 25%-40% of patients with blastomycosis have extrapulmonary dissemination, most commonly to the skin and bone [47,52].…”

“…Symptom onset after inhalation of conidia ranges between 3 weeks to 3.5 months [52]. 25%-40% of patients with blastomycosis have extrapulmonary dissemination, most commonly to the skin and bone [47,52]. In comparison to immunocompetent patients, the rate of disseminated disease is similar amongst SOT patients and immunocompetent patients, however presentation differs in the severity of pulmonary disease, which can often progress to ARDS [49,52,53].…”

“…Routine pre-transplant screening is not recommended, but testing should be considered in donors and recipients from endemic areas that have lung and skin lesions of unclear etiology [54]. In contrast to the other major North American endemic fungi, there have been no documented cases of Blastomyces transmission through an infected allograft [2,52].…”