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Department of Pathology, University of Oklahoma Health Sciences Center

NeuroTest Sample Question #27 Next question Previous question

Answer: Coccidioides immitis. Level of difficulty: 2 NeuroTest NeuroLearn NeuroHelp

Discussion:

Pathology of the case: The material was obtained from a patient with AIDS and encephalitis like syndrome On hematoxylin-eosin stained section, there are multiple small, concentric collections of chronic inflammatory cells (Panel A) within the brain parenchyma. On high-magnifications, a cyst can be seen at the center of these collections (Panel B). The cyst contains many small, round organisms. The wall and the contents are both strongly positive for GMS stain (Panel C). These organisms are consistent with mature spheurules of coccidioides immitis. Interestingly, the endospores are also strongly positive for PAS stain but the wall often turns out to be negative. There is also meningitis in this case (not shown). The pathology of this case is that of meningitis with underlying cerebritis due to Coccidioides immitis infection and associated with AIDS.

Coccidioides immitis:

Highly infections, dimorphic fungus.
Most often found in the southwestern United states, parts of Mexico, Central and South America for its tendency to inhabit dry, slightly, acidic soil.
The route of entry is through respiratory tract that can lead to a primary pulmonary infection. Less then 0.2% of the cases disseminate outside the respiratory tract.
The cysts as demonstrated here is usually 20-200 mm in diameter and the endospores are 2-5 mm in diameter. At maturity, the spherules rupture and release their endospores. The endospores gradually enlarge and become spherules that would discharge endospores as they mature.
The CNS is often the only extrapulmonary site involved due to dissemination with meningitis as the most common form. Coccidioides is unique among other fungal organisms in causing eosinophilic meningitis in more than half of the cases. Brain abscess is quite rare.
The majority of patients who develops coccidiodal meningitis are healthy before infection.
Immunocomprimised host are more susceptible to disseminated infection.

Comment: KarMing-Fung@ouhsc.edu