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NBME 21 Answers

nbme21/Block 1/Question#19 (40.9 difficulty score)
A 22-year-old man has had frequent episodes ...
C1 esterase inhibitor (binds activated C1r, C1s)🔍
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 +9 
submitted by mcl(534),
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notadoctor  Thought this was a trick question as C1 esterase deficiency also results in a decrease in C4. However, the second answer choice was not referring to C4 but to C4 binding protein, which I now know is different. I also didn't realize C1 esterase was technically a complement protein. +4  
youssefa  Based on many sources hereditary angioedema does NOT cause a rash (urticaria) which is a main differentiating point between angioedema and allergy. This mislead me in this question. Any clarification? +22  
ergogenic22  +1 on the above because uptodate states that c1 esterase inhibitor deficiency, both acquired and nonhereditary, are both non-urticarial, non-pruritic, and that is confirmed by the above linked article +2  
sahusema  Question writer probably didn't know the difference between cutaneous urticaria and subcutaneous edema. +3  
almondbreeze  same. got it wrong bc the pt didn't have sx of hereditary angioedema - swollen lips and eyelids +2  
teepot123  fa 19 pg 107 +  
beloved_bet  According to Amboss "Mast cell-mediated angioedema Often associated with urticaria and pruritus Other associated with clinical findings of allergic reactions (see type 1 hypersensitivity reaction) Presents within 30 minutes to 2 hours after exposure and resolves over hours to days" +1  



 +0 
submitted by abhishek021196(39),

Hereditary angioedema (HAE) caused by C1-esterase inhibitor deficiency is an autosomal-dominant disease resulting from a mutation in the C1-inhibitor gene. HAE is characterized by recurrent attacks of intense, massive, localized subcutaneous edema involving the extremities, genitalia, face, or trunk, or submucosal edema of upper airway or bowels. Routine long-term prophylaxis with either attenuated androgens or C1-esterase inhibitor has been shown to reduce the frequency and severity of HAE attacks.




 +0 
submitted by kolivera(3),

This is what I came across putting the two (angioedema + laryngospasm) together. Take into account that this info is regarding ACEIs but, I guess with a certain severity, angioedema can be associated with other sx. "However, angioedema has occurred suddenly after months to years of therapy, and about 20% of known cases of angioedema occurring in this context may involve severe symptoms (e.g., dyspnea, stridor, laryngospasm)."

https://www.sciencedirect.com/topics/medicine-and-dentistry/angioedema