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NBME 21 Answers

nbme21/Block 1/Question#19 (43.8 difficulty score)
A 22-year-old man has had frequent episodes ...
C1 esterase inhibitor (binds activated C1r, C1s)πŸ”

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submitted by mcl(579),
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itteanP yma vaeh eyaredhtri ednaamoge,i hwhic si saocedtsia ihtw cter"ernru ascttka of eetn,isn esvma,is ldcolezia ctsuanusuoeb deame invlionvg eht it,rstiemexe againtie,l ,ecfa ro ,uknrt ro ausluobcsm medae fo erupp irwaya ro e.obl"sw eTh rctaiel esog no to asy ertsse1-Cae" birtohiin wrosk redycilt no teh plemconmet and attocnc maapls sceacdsa to ureedc ndynarbiki reaeles" ihchw si alos yaorplbb ogod to .wnok


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  

submitted by syoung07(21),

seems this hereditary angioedema lacks well, everything that is hereditary angioedema. Thats some good family fun there eh Cotton

submitted by jsmoov(13),

This patient has ACQUIRED ANGIOEDEMA, which is different from Hereditary. In Hereditary you do NOT present with urticaria as mentioned by some previous comments.

Acquired angioedema (AAE) is characterized by acquired deficiency of C1 inhibitor (C1-INH), hyperactivation of the classical pathway of human complement and angioedema symptoms mediated by bradykinin released by inappropriate activation of the contact-kinin system.

submitted by abhishek021196(50),
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rieaedytHr nideaageom )EHA( dsecua yb aet1eesCs-r nrhiobiit ycendfecii si an miaotna-aodstonlum eeadsis entsuilgr ofrm a naumtito in het rCth-bini1io EHA is chcrdeireataz by rncreteur aascktt fo enenti,s emas,vis azdiecoll tsbcnoeuausu adeem gvinlnoiv het eiirtsem,etx ai,ltgiaen fae,c or r,ktnu ro ulssmbuaco eaemd fo ppreu wiayar or lwsb.oe ontueRi -rmnolegt lyhspiarpxo wthi tehier tnetduaeta soangdnre or eater-ssCe1 nhoibtiir ahs enbe whosn to ueecrd the nyceurefq adn sivrteye fo AHE satkcta.

submitted by kolivera(3),
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Tish si thaw I eamc rscaso ngtutpi het tow aegdioean(m + g)soyamparsnl keTa inot ncotauc htat tshi fnoi si ndiregrag ICAsE t,ub I gsues ihwt a tneacri evis,ryte adoeingeam nca eb asoaitcdes tiwh rothe .xs oHre"ev,w gedmianaoe sha ecdurcor ednuldsy aftre tsnhmo ot easyr fo ,atryehp dan oatub 02% of nownk csase fo odiegmanae irccruong ni tshi ttocenx mya oenvivl resvee momsspyt .(,.ge aedy,snp ,riodrst aonrms"gsaply.)