The Shape Shifters: Dimorphic fungi

Learning about fungi is hard enough even for infectious disease fellows (Narrator: especially for infectious disease fellows). By the time you learn how to differentiate the yeasts from the molds, the fungi kingdom decides to throw you a curve ball: Enter the shape shifters into the game of fungi learning – the dimorphic fungi.

The Dimorphic fungi shape shift depending on the weather (literally). They exist as molds in the great outdoors (environmental temperatures) and yeasts in the great indoors (inside our bodies at body temperatures). Clinically, this also means you will see the yeast forms in a histopathology review of a tissue sample, and our friends in the microbiology lab can re-create the environmental factors to grow them out as mold forms in culture. So essentially, they also shape shift between the microbiology lab and the pathology department. (They are sneaky Fung(uy)i…)

Some of the clinically relevant dimorphic fungi have a predilection for geographical location (endemic mycoses), and therefore are very popular in board exams to the dismay (or joy, after this review series?) of medical trainees.

#ClimateChangeIsReal isn’t just pertinent in the political arena, but also for these endemic fungi. The grave consequences of climate change might change and expand the geographical distribution(1,2) of these fungi and therefore result in more catch-up learning on our end. This is almost akin to learning the constant re-classification and re-naming of the fungi kingdom (thanks, no thanks taxonomists…)

In this review series, I will go over the endemic fungi in a ‘high yield’ approach that will hopefully be pertinent for both shelf exams/boards and clinical practice.

I’ve also purposefully made it a two-pager/per fungi review (or 1 pager if you print it double-sided, #SaveTheTrees). We will be providing PDF links with every Fungi review. This will be an easy reference for a pocketbook, handouts to print to teach your medical students or if you want to flex your knowledge of endemic fungi during rounds (All win-win-win situations!)

The profile of each shape shifter will be released every Friday in the spirit of #FungalFriday. The dimorphic fungi that will be covered during the #ShapeShifterSeries include:

  • Histoplasmosis
  • Blastomycosis
  • Coccidioidomycosis
  • Talaromycosis
  • Paracoccidiomycosis
  • Sporotrichosis

Our First Shape shifter in the series to be released this coming #FungalFriday will be Histoplasmosis, aka the Ohio valley disease/Cave disease. What does Ohio or caves for the matter have to do with this Fungus? Find out more this coming Friday!

Fatima Al Dhaheri, MBBS
The Fung(uy)i squad

1. The Lancet Infectious Diseases. Climate change: the role of the infectious disease community. Lancet Infect Dis. 2017;17:1219.
2. Greer A, Ng V, Fisman D. Climate change and infectious diseases in North America: the road ahead. CMAJ. 2008;178:715–722.

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