Blastomyces is a genus of dimorphic fungi known to be the causative agent of blastomycosis.
Like other dimorphic fungi, Blastomyces exists as hyphae on the colder end of the temperature spectrum, such as in dirt or soil.
Like the other dimorphic fungi, Blastomyces exists as yeast on the warmer end of the temperature spectrum, like in the body.
Blastomyces exists as a round yeast form.
The yeast form of Blastomyces is 5-15 micrometers, which is similar in size to a red blood cell (RBC).
Blastomyces can be visualized as single broad-based buds on sputum or tissue prep.
Blastomyces is also encapsulated with thick doubly-refractive walls that help with diagnosis when visualized in sputum or tissues.
Blastomyces is endemic to areas east of the Mississippi River and around the Great Lakes.
Blastomycosis can present as an acute illness resembling bacterial pneumonia, with symptoms of high fever, chills, productive cough and pleuritic chest pain. Lung disease caused by blastomycosis can easily spread to the skin and bones.
Blastomycosis can cause skin lesions with ulcerations and small pustules. Additionally, it can lead to verrucous skin lesions that often resemble squamous cell carcinoma (SCC).
Blastomycosis can disseminate to the bone causing local pain, joint pain and lytic lesions.
Blastomycosis has been known to disseminate in normal, immunocompetent hosts, in which it leads to mixed suppurative granulomas in the lungs or causes granulomatous nodules on the skin. This happens because of a limited ability to phagocytize the organism alongside continued recruitment of neutrophils and alveolar macrophages.
Itraconazole is usually used to treat blastomycosis, as it has been shown to be effective and well-tolerated with minimal side effects. However, many different medications from the "-azole" class have been used to treat blastomycosis in respective circumstances.
Amphotericin B is a medication reserved for systemic blastomycosis because of its side effect profile. It is also commonly used to treat blastomycosis with CNS involvement because of its penetration of the blood-brain-barrier.
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