NBME 16 Amphotericin B (NBME Answers)

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submitted by ∗lsp1992(24)

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Can someone please explain what we're seeing on the histo slide? I chose the correct answer because I was thinking fungus because of the immunocompromise and neutropenia (and I thought PAS was used for aspergillus), but I don't see anything fungus-related on that slide.

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cassdawg I think this is Blastomyces (broad based buds) where the darker pink are the blastomyces budding. Here are some similar slides: https://images.slideplayer.com/25/7691707/slides/slide_39.jpg https://www.gettyimages.co.uk/detail/photo/blastomycosis-in-the-brain-caused-by-the-high-res-stock-photography/vis303384 It could also be cryptococcus potentially (https://www.omicsonline.org/publication-images/diagnostic-pathology-budding-cryptococci-3-139-g005.png) but I think the bud bases are too broad and there is no clearing/visible capsule that cryptococcus is notable for. Either way you treat both systemic mycoses with amphotericin. +10

passplease How did you eliminate CMV? +2

cassdawg For me, CMV would have the characteristic "owl eye intranuclear inclusion" cells on biopsy but would be less likely to show anything in pleural fluid (i.e. thoracocentesis would not be used to diagnose CMV). Further CMV pneumonitis is an atypical/interstitial pneumonitis (diffuse patchy infiltrates on CXR, FA2020 p683) and he has a lower lobe consolidation with pleural effusion (more characteristic of fungal pneumonia). +6

shervinbd Looks like Cryptococcus neoformans to me. +4

chaosawaits I was pretty confident that this is Cryptococcus but the more I look at it, the more I don't know +1