Fungal organisms in the brain (February 2017)

TO THE EDITOR: In their Clinical Picture article in the February 2017 issue, Barbaryan et al¹ describe brain lesions in a young woman with human immunodeficiency virus infection who presented with seizures. Figure 3 illustrates Grocott-Gomori methenamine silver (GMS)-positive fungal organisms in a brain biopsy. The organisms appear helmet-shaped and crescent-shaped and contain an intracystic dot, morphologic features of Pneumocystis jiroveci cysts.² We could not appreciate features of Histoplasma yeasts (smaller yeasts with diameter of 3 to 5 µm, oval to tapered shape, and narrow-based budding).

The distinction between the two organisms can occasionally be challenging because there is some degree of overlap in size and shape, and both are GMS-positive. It is interesting that in the current case, serologic studies for Histoplasma were positive. Multiple infections with opportunistic organisms are not uncommon in severely immunocompromised individuals, and it is possible that the patient may also have had concurrent histoplasmosis. Brain lesions caused by Pneumocystis, although rare, have been previously reported.^3–5 Immunohistochemistry for Pneumocystis may be of interest in this very unusual case.

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