What Is Blastomycosis?

Blastomycosis, or "blasto" for short, is a fungal disease found in humans, dogs, and other mammals, occasionally cats. It is commonly misdiagnosed, often as cancer, Valley fever, Lyme disease, and other viral infections. It lives as a mold in warm (room temperature), acid, sandy soils near water. Once in the body, it lives as a yeast. It is contracted most often by inhaling through the nose the spores of the Blastomyces dermatitidis fungus. Blastomycosis is called a biphasic organism because it can grow in the environment as a fungus and within a mammal as a yeast.

In humans, blastomycosis is also known as Gilchrist's disease, Gilchrist’s mycosis, Blastomyces dermatitidis, and Chicago disease.

Without proper diagnosis and treatment, Blastomycosis can be fatal.

Blastomycosis was first described by the French botanist and biologist Philippe Edouard Léon Van Tieghem (1839-1914) in 1876.


  • T. C. Gilchrist: A case of blastomycetic dermatitis in man. The Johns Hopkins Hospital Reports, 1896, 1: 269-290.
  • T. C. Gilchrist: Protozoan dermatitidis. Journal of Cutaneous and Genito-Urinary Diseases, New-York, 1894, 12: 496.
  • T. C. Gilchrist and W. R. Stokes: The presence of an Oidium in the tissues of a case of pseudo-lupus vulgaris: preliminary report. Bulletin of the Johns Hopkins Hospital, Baltimore, 1896, 7: 129-137.
  • T. C. Gilchrist and W. R. Stokes: A case of pseudo-lupus vulgaris caused by Blastomyces. The Journal of Experimental Medicine, New York, 1898, 53-83.

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