Blastomycosis.

Blastomycosis is an endemic mycosis that occurs predominantly in North America in the north central United States and provinces of Canada, southern states, and those midwestern states that border the Mississippi River basin. It causes acute and chronic pneumonias and disseminated infection with cutaneous lesions as the major extrapulmonary manifestation. However, the vast majority of infected persons are asymptomatic or have mild respiratory symptoms that are not diagnosed as being caused by a fungal infection. Rarely, patients develop severe pulmonary infection that progresses to acute respiratory distress syndrome (ARDS), which has a high mortality rate. A urinary antigen test is now available to aid in diagnosis, but it is not specific and is positive in patients who have histoplasmosis as well as blastomycosis. Antibody assays remain nonspecific and insensitive, and the confirmatory diagnostic test is still growth of the organism in culture. Updated guidelines from the Infectious Diseases Society of America are available to aid clinicians in the management of the various forms of blastomycosis.