This disease is caused by a fungus, C. immitis, and can thus be treated with azole drugs if symptomatic.
Coccidioides immitis is a dimorphic fungus that is endemic to the southwestern United States. Unlike the other systemic dimorphic fungi, coccidioides exists in tissue as a spherule that is 20-60 um, and not as a yeast. It grows as a yeast in warmer temperatures (37 degrees C), and as a mold with hyphae at cooler temperatures (20 degrees C).
Coccidioides immitis is endemic in the Southwest including Arizona, California, Nevada, and New Mexico. It also resides in northern Mexico and parts of Central and South America.
This organism resides in the soil, and the spores are swept into the air when the soil is disrupted, such as during construction, farming, or after earthquakes. Earthquakes are especially associated with tremendous increases in case rates of Coccidioidomycoses.
The disease is spread by inhaling arthrospores, which turn into spherules in tissue that contain endospores within a thick refractive wall.
The spherules measure 20-60 um and contain endospores within that measure slightly larger than a RBC.
The spherules rupture and endospores spread throughout the body causing disease, most commonly in the lungs. Therefore, this organism most commonly causes pneumonia.
C.immitis can spread to the CNS and cause meningitis with granulomatous lesions.
Coccidiomycosis can spread to the bones and cause osteomyelitis with granulomatous lesions.
Coccidiomycosis can cause ulcerating or pustular skin lesions when disseminated to the skin. Erythema nodosum is not a sign of dissemination, but is rather an immune response.
A skin finding not specific to coccidioimycosis, but commonly found in infection that presents as red, painful nodules on extensor surfaces like the shins.
C. immitis causes a granulomatous inflammatory reaction in the body, characterized by granulomas that wall off the endospores unable to be phagocytosed by macrophages.
Coccidioimycosis causes caseous necrosis, which is a type of necrosis characterized by a creamy white cheesy necrotic debris.
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