NBME 21 Increased vascular permeability (NBME Answers)

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Retired NBME 21 Answers

nbme21/Block 1/Question#15 (reveal difficulty score)
A 35-year-old man comes to the physician ...
Increased vascular permeability 🔍 / 📺 / 🌳 / 📖
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submitted by ∗neonem(630)

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This is a case of acute gout. Monosodium urate crystals are taken up by neutrophils, leading to an acute inflammatory reaction. T-cells aren't really involved in gout (more rheumatoid arthritis).

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hungrybox Great explanation! So frustrating that I got this wrong, should have been easy. +4

temmy the way i thought about it was how did the neutrophils get there? the answer is via increased vascular permeability +18

nor16 they, unfortunately, did not ask " how did neutrophils get there" but " whats the cause of the swelling " not to confuse with " what causes the swelling " +2

divya absolutely right temmy. that's how i thought about it too. +1

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submitted by ∗sweetmed(157)

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The chemotactic factors produced by monocytes and mast cells and the local vasodilatation stimulates neutrophilic chemotaxis. Also, endothelial cells activation further aggravates the inflammatory response and migration of neutrophils. This leads to an influx of neutrophils locally.

refrence: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5512152/

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bronchophony Why not complement activation? +3

joyceeepan the way i though about it was: you need antibodies (IgG/IgM) to activate the complement system. But there's no such a thing as an anti-gout antibody. (and it is not an infection neither) +3

an_improved_me Thats not exactly true for a couple reasons. I saw a UWorld question that said something along the lines of an ApoProtein being useful b/c it binds the urate crystals, and makes it less likely for the crystals to be opsinized/recognized by neutrophils. Therefore, Abs do play a role. Secondly, you can have activation of coplement via the alternative pathway, which does not require ABs. +2

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submitted by ∗skip_lesions(17)

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Can't histamine also cause swelling or is it just not involved in the pathology of gout?

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zevvyt yes. Histamine causes vasodilation and increased vessel permeability. But it's not involved in Gout. Gout is more about Neutrophils and Macrophages activating eachother and not really about Mast cells. +5

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