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Coccidioides immitis

Reviewer: Elliot Weisenberg, M.D. (see Reviewers page)
Revised: 26 February 2014, last major update September 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Clinical features

● Dimorphic fungus that reproduces by endosporulation, found in soil in Southwest US, San Joaquin Valley (California), Mexico, Central America
● May induce chronic pneumonia with mass-like lesion resembling tuberculosis
● Disease usually limited to lung, sometimes with regional lymph node involvement, usually in immunocompetent patients
● In endemic areas, inhalation of spores usually leads to subclinical infection with delayed type hypersensitivity response
● 10% of infected individuals develop “San Joaquin Valley fever” with fever, cough, chest pain, lung lesions, erythema nodusum
● Disseminated disease is rare
● In lab, hyphae form infectious arthrospores, requires careful handling

Gross description

● Mass with necrotic center surrounded by fibrous tissue with concentric lamination
● Fungus ball may fill pre-existing pulmonary cavity

Micro description

● Granulomatous inflammation, large thick-walled spherules contain variable sized daughter cysts
● Pyogenic reaction occurs with release of endospores from rupture of spherules
● Variable fibrocaseous granulomata, military disease, pyogenic inflammation
● Immature nonendosporulating spherules can resemble nonbudding forms of Blastomyces dermatitidis (Can Respir J 2008;15:377)

Micro images

69 year old man with a history of COPD

69 year old man with a history of COPD (cont.)

Various images - not necessarily lung

Cytology images

Bronchoalveolar lavage - immature variant (GMS stain)

Positive stains

● In situ hybridization may be useful (Diagn Mol Pathol 2010;19:99)

End of Lung-nontumor > Infections > Coccidioides immitis

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