Blastomycosis

Blastomycosis is an invasive infection caused by the dimorphic fungus Blastomyces dermatitidis, endemic to the north central and southern US, Canada, and parts of Africa.

Most commonly involves the lungs. Dissemination can occur, with extrapulmonary infection often seen in the skin, bones, joints, central nervous system, and genitourinary system.

Although key epidemiologic factors in the history are often suggestive of the diagnosis, histopathologic or microbiological examination of clinical specimens with demonstration of B dermatitidis is necessary to establish the diagnosis.

First-line treatment for ambulatory patients is a prolonged course of oral itraconazole. Amphotericin-B is reserved for patients with more severe disease or for patients in whom itraconazole is contraindicated.

No vaccine is available for disease prevention.

Blastomycosis is an invasive infection caused by the dimorphic fungus B dermatitidis, which is endemic to the upper and mid-Mississippi River valley in the US, Canada, the Mediterranean basin, and parts of Africa.[1]Castillo CG, Kauffman CA, Miceli MH. Blastomycosis. Infect Dis Clin North Am. 2016 Mar;30(1):247-64. http://www.ncbi.nlm.nih.gov/pubmed/26739607?tool=bestpractice.com [2]Thompson GR 3rd, Le T, Chindamporn A, 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;21(12):e364-e374. http://www.ncbi.nlm.nih.gov/pubmed/34364529?tool=bestpractice.com Although pulmonary involvement is most common, skin, central nervous system, and osteoarticular involvement are frequently seen. Less commonly, infection can involve other sites such as the genitourinary system, and patients can even have multiple sites of infection.

Diagnosis is usually based on either histopathologic demonstration of the characteristic yeast form or culture of the mycelial form from clinical specimens.[3]Wheat LJ. Antigen detection, serology, and molecular diagnosis of invasive mycoses in the immunocompromised host. Transpl Infect Dis. 2006 Sep;8(3):128-39. http://www.ncbi.nlm.nih.gov/pubmed/16913971?tool=bestpractice.com There are no commonly accepted schematic classifications for blastomycosis, including formal criteria for severity of illness. [Figure caption and citation for the preceding image starts]: Direct potassium hydroxide preparation at 40x magnification of a sputum specimenNancy L. Wengenack, PhD, D(ABMM), Director of Mycology and Mycobacteriology Laboratories, Assistant Professor of Microbiology and Lab Medicine, Mayo Clinic, Rochester, MN [Citation ends].[Figure caption and citation for the preceding image starts]: Direct potassium hydroxide preparation at 20x magnification of a sputum specimenNancy L. Wengenack, PhD, D(ABMM), Director of Mycology and Mycobacteriology Laboratories, Assistant Professor of Microbiology and Lab Medicine, Mayo Clinic, Rochester, MN [Citation ends].