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NBME 24 Answers

nbme24/Block 4/Question#5
A 45-year-old man comes to the physician ...
Muscle biopsy🔍

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 +15  upvote downvote
submitted by sattanki(50),

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.

sympathetikey  That's what you get for killing polar bears. +34  
dr.xx  That's what you get for not cooking them well. +2  
charcot_bouchard  Theres nothing called "well cooked polar bear meat" +2  

 +6  upvote downvote
submitted by neonem(450),

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?

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

+3/- sunshinesweetheart(46),

 +0  upvote downvote
submitted by madojo(93),


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

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 :/

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 +  

 +0  upvote downvote
submitted by haozhier(3),

How do you guys know about this? I chose stool O&P...and muscle biopsy is not mentioned anywhere...

misterdoctor69  Sketchy micro! +  

 +0  upvote downvote
submitted by hungrybox(578),

vs. eggs (ova) in stool → Hookworms*, Ascaris

vs. larvae in stool → Strongyloides stercoralis

vs. scotch tape test → E vermicularis

hookworms → Necator Americanus, Ancylostoma duodenale

(source: sketchy)

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