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NBME 24 Answers

nbme24/Block 4/Question#41

A 30-year-old man who is a migrant farm worker ...

Formation of hypnozoites

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The blood smear depicts Schuffner stippling. Found the exact image on the web with explanation:

http://spot.pcc.edu/~jvolpe/b/bi234/lec/2_parasites/images/P._vivax.htm

doctorboomboom  Hey thanks for finding the image! Do you know why the answer can’t be Chloroquine resistance? I was b/w that and formation of hypnozoites. +1  
jejunumjedi  I think it's just that Schuffner stippling and hypnozoites are both specific to vivax and ovale species. These species could be chloroquine resistant or sensitive, but if you have Schuffner stippling or hypnozoites, you can definitively say that it's either vivax or ovale. +1  
sherry  Species with hypnozoites is not called chloroquine resistant. Chloroquine-resistant species means trophozoite/schizont cant be killed by chloroquine. We dont have enough info to decide whether the spp in the q is resistant/sensitive. But we do know he moved from Honduras to USA 1 year ago. +1  
soph  UW: in africa most malaria species are resistant to chloroquine. he is from hondruas +  
randios  Can anyone explain the 1-week history of fever? Ruled out vivax and ovale due to 48 hr cycles. Or did they just throw that in as an unspecific symptom. +  




 +2  upvote downvote
submitted by leny123(2),

General rule - Chloroquine sensitive if from Caribbean or Central America west of Panama Canal, this patient immigrated from Honduras so you can eliminate chloroquine resistance as an answer choice (in addition to the vivax/ovale info above).

charcot_bouchard  Guys along with all intelligent discussion also keep in mind he immigrated 1 year back. So it must be hypnozoites which is causing this because Murica is Malaria free. +6  




 +1  upvote downvote
submitted by yotsubato(282),

Kind of tricky question. The hypnozoites are chloroquine resistant. But the species may not be.

P. Falciparum is resistant and looks like a banana, but you dont know if the malaria in the RBC is falciparum or not.





Found this great document with slides about the different pathogens: http://ncasmbranch.org/meetings/2019SprPpts/2019-03_Spring_Garcia.pdf





I think chloroquine resistance wont be specefic to vivax and ovale,thus making it the incorrect answer. Chloroquine resistance can apply to P. Falciparum and P. Malariae

Only vivax and ovale cause hypnozoite thus making that the more clear answer





Does anyone know how to rule out E? I've never learned about microorganisms specifically activating a cell's CAMs, but when I looked it up, I found this article (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC395703/). The article doesn't specifically mention plasmodium as using it, but several of the resources for the article does.