NQ-122: (E) Coccidioides immitis

Pathology of the case: Among all of the entities here, Coccidioides is the largest. This allows it to be separated from many other fungal organisms. In all of the 5 organisms being listed here, they can all be seen in the central nervous system. Histoplasma, Coccidioides, and Blastomyces are often due to systemic dissemination and not associated with compromised immunity. Cryptococcus and Toxoplasma, in contrast, do not cause major problem in most healthy patients but can be serious conditions for immune compromised patients such as HIV(+) patients.

Coccidioides (black arrows) is one of the few fungal organisms that can be recognized with hematoxylin and eosin stain without the use of special stains. Histologically, the fungus is large, ranging from 10 to 80 μm in size, and contains numbers spherules with thick, refractile wall. Like other fungal organisms, they are well demonstrated by GMS and PAS stain.

Coccidioides immitisfungus is native to the San Joaquin Valley of California. Together with  Coccidioides posadasii which is endemic to certain arid-to-semiarid areas of the southwestern United States they are the two most commonly seen organisms that cause coccidioidomycosis in the United States. Coccidioidomycosis is usually transmitted by inhalation of airborne spores. In contrast to other conditions being mentioned in this quiz, Coccidioidomycosis is not associated with compromised immunity. [Click on this link to see online information on blastomycosis of the CNS] [Click here to see online information of histoplasmosis of the central nervous system]