How does treatment of disseminated Blastomycosis change based on the presence or absence of CNS findings?
In cases of Blastomycosis without CNS involvement, treatment typically involves azole drugs such as itraconazole. In severe cases and those with CNS involvement, treatment initially consists of intravenous Amphotericin B before azole treatment.
What regions are classically associated with Blastomycosis exposure?
Blastomycosis is endemic to North America, in particular the Ohio and Mississippi River Valleys, the St. Lawrence River Valley, and the Great Lakes regions.
What is the estimated prevalence of Blastomycosis in endemic regions?
In endemic regions, estimated prevalence is approximately 1 to 2 cases per 100,000 per year.
What laboratory tests are used to diagnose Blastomycosis?
Diagnostic methods include culture (gold standard obtained via saliva, respiratory samples, lung biopsy, skin, or other infected tissue), histopathology, and urine test for Blastomyces antigen.
What morphology does Blastomycosis exhibit on histopathology slides?
Morphology is confirmed via visualization of round, multinucleated yeast forms that produce daughter cells from a single broad-based bud.
What is the pathogenesis of Blastomycosis in humans?
Primary infection site is the lungs due to inhalation. Alveolar macrophages will typically phagocytose and clear the conidia. After transformation to yeast form, it is more difficult to clear due to the presence of a thick capsule. Infection spreads from lungs lymphohematogenously most commonly to the skin, bones and less commonly, genitourinary system. At both the primary site and sites of distant spread, a suppurative response will occur followed by formation of noncaseating granulomas.
Multiplanar multisequence MR images demonstrate a T1 intermediate, T2/STIR hyperintense osseous lesion involving the distal tibial metaphasis with erosion through the cotex and periosteum and extension into the surrounding anteromedial soft tissues. There is associated homogeneous enhancement on post contrast images. This lesion closely abuts the physis in this skeletally immature patient.
Surrounding this lesion, there is extensive soft tissue edema. There is no subperiosteal fluid to suggest subperiosteal abscess although the adjacent periosteum is slightly elevated. The lesion is poorly marginated in the bone and there is no T1 hyperintense penumbra. To a lesser extent, there is edema and enhancement in the medial tibial epiphysis.