NBME 24 Failure of conversion of N5-methyltetrahydrofolate to tetrahydrofolate (NBME Answers)

NBME 24 Answers ↦

nbme24/Block 2/Question#1 (48.2 difficulty score)
A 73-year-old woman has had easy fatigability ...
Failure of conversion of N5-methyltetrahydrofolate to tetrahydrofolate🔍
tags:

+9
submitted by yex(93),

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nAirocgcd to :janolG 21"B l(b)cnoaiam hsa obltac in .it itcrCgiaunl mrof fo aoetlf si teefadlermhltaoy.oyrhtt rseuPop of cbmlaniao 1)2B( is to aekt eht mlhtye ouprg off of amtdttrho.areeyteloyflh enhT ’sit ldaecl oe.hyolaefrrtdatt If ouy n’tdo get the mehlyt ogurp fof fo tlea,of you lwli tno kema AD.N oS, if ouy aer 2B1 e,fd you ’tnac etg hte hymtel proug off dan nnocat eamk N.AD If uoy rae fed in ote,alf ouy ntc’a emka .N"AD

misterdoctor69 lmao +

pic of the methionine/folate cycle: https://i.imgur.com/XXWXTT7.png

+2/- hungrybox(968),

+7
submitted by lsmarshall(393),

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lthhoguA hsnoC'r yam hvea cl,urse ius,atfls nda ni;degbel ti auluyls esod ont auesc roni cicfedyeni iaanem nad sha ssel eedblgni hatn C.U alt"rtrucuS neibslatmiora of het almniter elium, chsu as ornCh eeasdsi nda lugriasc seoce,irtn cna seauc resdacede tairnboosp of ivintam ".1B2 - tirFs idA lrnGaee eilrpsnciP

+5
submitted by syoung07(21),

would have been real neato if they threw in a hyper-segmented neutrophil

+3
submitted by lispectedwumbologist(103),

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Wyh luwod it nto eb iemana of hnocric seeadis ithw eedersadc usrme aferrnsnrit ?icetcoannortn

lispectedwumbologist Nevermind I'm stupid as fuck I see my mistake +1

drdoom be kind to yourself, doc! (it's a long road we're on!) +20

step1forthewin Hi, can someone explain the blood smear? isn't it supposed to show hypersegmented neutrophils if it was B12 deficiency? +1

loftybirdman I think the blood smear is showing a lone lymphocyte, which should be the same size as a normal RBC. You can see the RBCs in this smear are bigger than that ->macrocytic ->B12 deficiency +22

seagull maybe i'm new to the game. but isn't the answer folate deficiency and not B12? Also, i though it was anemia of chronic disease as well. +

vshummy Lispectedwumbologist, please explain your mistake? Lol because that seems like a respectible answer to me... +9

gonyyong It's a B12 deficiency Ileum is where B12 is reabsorbed, folate is jejunum The blood smear is showing enlarged RBCs Methionine synthase does this conversion, using cofactor B12 +

uslme123 Anemia of chronic disease is a microcytic anemia -- I believe this is why they put a lymphocyte on the side -- so we could see that it was a macrocytic anemia. +2

yotsubato Thanks NBME, that really helped me.... +1

keshvi the question was relatively easy, but the picture was so misguiding i felt! i thought it looked like microcytic RBCs. I guess the key is, that they clearly mentioned distal ileum. and that is THE site for B12 absorption. +6

sahusema I didn't even register that was a lymphocyte. I thought I was seeing target cells so I was confused AF +

drschmoctor Leave it to NBME to find the palest macrocytes on the planet. +4

+1
submitted by sunshinesweetheart(69),

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ymtcicoarc nmiaae sen(e in oldbo em)asr = RCB rerupscors anc gwro ubt ton ediidv

avol csroaetycm (eens in ldoob )emsra = aelcltagbmsoi anaemi if( htye ot'dn swoh runtophile ghntreaynpet)imeso

1B2 sha cluoionrge msmysotp and low iclaloeytmhmn acdi hlewi oaetlf fneycecidi dose ton

eltfoa si absdboer ni u,ejjmun 1B2 ni umeil

u saecs of B12 feyneiicdc = ieicupnsor m,naeai yetgmcasto,r iaell ni,eestcor sihf wrapem,to m sevngai

D) aeirlfu of FHRMT --g;t& FHT (vai nfsttarymeshlaree = 21B diiyncefec dna moactrcyci amanie

B) DPG6 cfeceiyind = omnioycrct buceeas fo cinr CBR tstnioerduc; tp lwodu wohs lsairacartunv olisheyms sx itpditeercpa by an oivaextdi sssrtero

C) npoyprhtoopoinerg aexsdio dyieenifcc = rciimctyoc iaaenm abceues fo wol mhee tiysssehn

)A ercd irrnrtenafs = hihg rirfntie = maanie fo inohrcc aeisdse = imicytocrc imanae sbucaee fo olw nori

+1
submitted by krewfoo99(88),

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floci ciad wehn ti seetrn teh ybod si ni eht mofr of yahrhlrldtfeoottemtaye FT(H thad.eemly)t It otaesnd tis yltmhe ropgu ot vntimai 2B1 ot oeemcb FHT the( eiacvt rmof hhwci sa a DAN r.)escpourr e hT aivtimn 12B ihwt its thmlye grupo ogse on ot nembioc hwti enciyotmeho ot romf onimteneh.i