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Retired NBME 24 Answers

nbme24/Block 4/Question#5 (reveal difficulty score)
A 45-year-old man comes to the physician ...
Muscle biopsy ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
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submitted by โˆ—sattanki(82)
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Muscle pain + periorbital edema is a classic presentation for trichonella spiralis. Best diagnosis for this is a muscle biopsy, as the wormy likes to hangout within the muscles.

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sympathetikey  That's what you get for killing polar bears. +98
dr.xx  That's what you get for not cooking them well. +8
charcot_bouchard  Theres nothing called "well cooked polar bear meat" +2
jbrito718  fun fact: Can get vitamin A toxicity from eating polar bear meat which leads to fatal fulminant hepatitis! +4
stresssweat  actually got this question right as a fluke bc i guessed vitamin A toxicity due to polar bear meat leading to muscle damage +


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 +10  upvote downvote
submitted by โˆ—neonem(629)
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Apparently trichinella lies around in muscle of all of the random exotic animals that most people wouldn't normally eat... things like bear, wild boars/pork (like in Sketchy Micro), big cats, foxes, dogs, horses, seals, walruses. In case you needed another reason to not hunt and consume these animals?

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how to rule out the others:

we would see eosinophilia, but obvi this wouldnt tell us which helminth is involved

Trichinella larvae bury themselves inside muscle tissue rather than remain in the intestine as in other roundworm infections, so stool sample tests don't often show evidence of the parasite

gram stain of stool is a pretty nonspecific test used for campylobacter enteritis; this dude doesnt have diarrhea...and lastly, xray of muscle aint gonna tell u a thang lolz


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 +3  upvote downvote
submitted by โˆ—hungrybox(1277)
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vs. eggs (ova) in stool โ†’ Hookworms*, Ascaris

vs. larvae in stool โ†’ Strongyloides stercoralis

vs. scotch tape test โ†’ E vermicularis

hookworms โ†’ Necator Americanus, Ancylostoma duodenale

(source: sketchy)

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 +2  upvote downvote
submitted by jucapami(14)
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https://www.cdc.gov/parasites/trichinellosis/biology.html worth taking a look.

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submitted by โˆ—bharatpillai(40)
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Just adding on- Xray of large muscle groups would help in diagnosis of cysticercosis since cysts are calcified, in trichinella they are not. I think i'm the only one who got this wrong :/

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misterdoctor69  Maybe so, but I think that if we get any questions concerning cysticercosis, it would be neurocysticercosis, so you'd do brain imaging instead... Additionally, as per the CDC: muscle cysticercosis is usually nontender?: https://www.cdc.gov/parasites/cysticercosis/gen_info/faqs.html +
brs  I think everyone who has watched House M.D. S1 E1 gets a chance to make it wrong. +


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submitted by โˆ—haozhier(23)
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How do you guys know about this? I chose stool O&P...and muscle biopsy is not mentioned anywhere...

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misterdoctor69  Sketchy micro! +


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submitted by โˆ—madojo(212)
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https://www.google.com/url?sa=i&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwi_15-2tYfmAhXEGDQIHUx4D1MQjRx6BAgBEAQ&url=https%3A%2F%2Fquizlet.com%2F355174098%2Fsketchy-micro-super-worms-enterobius-vermicularis-ancylostoma-duodenale-necator-americanus-ascaris-lumbricoides-strongyloides-stercoralis-trichinella-spiralis-intestinal-nematodes-diagram%2F&psig=AOvVaw0NZl1rWBeFkgoYNiM5nwJb&ust=1574841902769110

SKETCHY trichenlla spiralis pig (can be polar bear too) * round glasses --> perio orbital edema sweating and green vomit round things on walls ==> forms cysts in striated muscle (so for this question makes sense that you do muscle biopsy) fire --> inflammation of muscle eosinophil granules --> non specific as you can see its all over this image so its for many different types of nematodes

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