Blastomycosis

Blastomycosis is a primary systemic mycosis resulting from infection with Blastomyces dermatitidis, typically initiating in the lungs after inhalation of environmental spores ^[1][2]. The organism persists in soil and decaying organic matter such as wood or leaves, from which airborne propagules are liberated ^[2]. Disease presentation may be confined to the respiratory tract or extend hematogenously to extrapulmonary sites ^[2].

Around half of infected individuals are asymptomatic; when symptoms occur, they typically develop between three weeks and three months after spore inhalation and include fever, cough, night sweats, muscle pain, weight loss, chest pain, and fatigue ^[2]. The lungs are involved in approximately 79% of cases, and in 25–40% of cases the infection disseminates to other organs, most notably the skin, where lesions classically appear as crusted purplish warty plaques with a roundish bumpy edge and central depression ^[2][4]. Disseminated disease can also affect the bones and central nervous system, with the extent of spread influenced substantially by host immune status ^[2].

The global burden of endemic mycoses, including blastomycosis, continues to rise annually and they remain a leading cause of infectious morbidity and mortality worldwide ^[3][4]. Blastomycosis is classically endemic to the eastern United States and Canada, especially the Ohio and Mississippi River valleys, the Great Lakes region, and the St. Lawrence corridor ^[2]. Over recent decades, infections have been reported with increasing frequency in areas previously considered non-endemic, a shift attributed to greater use of immunosuppressive medications, improved diagnostics, heightened disease recognition, migration, increased travel, and climate change ^[4]. Some studies in the United States show a disproportionately high incidence and mortality among Black people, while Canadian data suggest elevated incidence among First Nations populations, including children, though these patterns may be confounded by residential location and access to medical care ^[2].

Infection occurs through inhalation of fungal spores aerosolized from soil and decaying organic matter such as wood or leaves harboring Blastomyces dermatitidis ^[2]. Outdoor activities that disturb these substrates, including hunting or camping in wooded areas, increase the risk of acquiring blastomycosis ^[2].

There is no vaccine against blastomycosis, but the risk of disease can be reduced by avoiding disturbance of soil in areas where the organism is known to occur ^[2].

1. 1Wikidata contributors. blastomycosis [Internet]. Wikidata. cited 4 Sept 2026.Available from: https://www.wikidata.org/wiki/Q627368
2. 2Wikipedia contributors. Blastomycosis - Wikipedia [Internet]. Wikipedia. cited 12 Aug 2026.Available from: https://en.wikipedia.org/wiki/Blastomycosis
3. 3Thompson GR 3rd et al. Global guideline for the diagnosis and management of the endemic mycoses: an initiative of the European Confederation of Medical Mycology in cooperation with the International Society for Human and Animal Mycology. Lancet Infect Dis. 2021 Dec. PMID: 34364529. doi: 10.1016/S1473-3099(21)00191-2.PubMed: https://pubmed.ncbi.nlm.nih.gov/34364529/
4. 4Ashraf N et al. Re-drawing the Maps for Endemic Mycoses. Mycopathologia. 2020 Oct. PMID: 32040709. doi: 10.1007/s11046-020-00431-2.PubMed: https://pubmed.ncbi.nlm.nih.gov/32040709/