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

NBME 24 Answers

nbme24/Block 2/Question#1 (reveal difficulty score)
A 73-year-old woman has had easy fatigability ...
Failure of conversion of N5-methyltetrahydrofolate to tetrahydrofolate 🔍 / 📺 / 🌳
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+20
submitted by ∗sympathetikey(1535),

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tiasonuMt in MTL1-T haot(nlyclModiir ecedond RAtN ienlcue )1

A mmcono tnmuaito si 3.A2G34 anC surtel ni eupmtlil haiotcnimrodl eidniefcesci dan eaicstaosd dsrdeo.ris It si astaocsdei wt:hi

adMrhionoltci yoaoaneecphpthlym
Ltacic sicdisoa
tliorekSk-e esodsepi S)M(EAL

MSAEL si a erra nolmthcioirad rsriodde wnokn to aefctf amyn astpr of the ody,b syaillepce het nvusoer ssymte and the .rbina msyoSptm of SLAME nucdlei:

eeRtuncrr evsere ahascedhe
ecuMsl eneskaws tmaphy)(oy
Hrnaieg loss
kkloitreeS- edospise htwi a ossl of ,ussescoiosncn ,seiesruz nda htroe srboelpm aicgefnft eth nreuovs meysst.

uorceS: .in:ip/hLid-eMgakkT.p/iTtse1t/row/wi

+11
submitted by ∗yex(120),

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rngdocciA ot ol:Gnaj 2"1B n(boacl)mia has blacot in i.t nicultgCira rfmo fo etoalf is lytler.ohoeamtrdehttfya Proseup fo cminabloa 2(1)B is ot tkae hte lyehtm gropu fof of frdeerayttomthyl.otlhea hneT is’t allcde aoayedo.ehrtfrttl If ouy otnd’ etg eht lhtyme uorgp ffo fo to,ealf uyo lliw tno kmea D.AN ,oS fi you aer 12B ,efd you cta’n tge teh mhylte opgru fof nda cnotan ekma .NDA If uoy ear fde ni o,elatf ouy n’cat make "NDA.

misterdoctor69 lmao +

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

+2/- hungrybox(1207),

+11
submitted by ∗syoung07(47),

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wdulo eahv nbee aelr tnaeo if teyh rhwte in a pstmn-eerhedyeg nloiptuhre

+7
submitted by ∗lsmarshall(452),

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hlhtoAug so'Chnr amy hvae erucls, ,slfstiau dna ie;edglbn ti uualyls does otn ecuas nroi eeyiicdnfc mineaa adn sha essl lebdnieg hant UC. tutr"Sluacr lmiranateisob of teh etrlinam eimlu, ucsh sa Crnoh idessae adn glirsauc oicn,esrte anc uscae aesddcree oipraonsbt of ainmvit 1"B2. - irstF Adi Gnerael irpscnelPi

+3
submitted by ∗lispectedwumbologist(118),

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yWh dlowu it not be maiean of rcchoin daissee hwti creedesad emusr eiansrtrfrn ctnoein?tocran

lispectedwumbologist Nevermind I'm stupid as fuck I see my mistake +2

drdoom be kind to yourself, doc! (it's a long road we're on!) +21

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 +25

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 +2

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. +4

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. +5

zevvyt so i guess size is more important than color cause those are hypochromatic as fuck +

yesa The NUCLEUS of a lymphocyte should be the same size as a normal RBC, which is not the case here. Under normal circumstances RBCs are not as big as lymphocytes, so this is truly extraordinary = megaloblastic anemia. +1

weirdmed51 @yesa you mean ‘macrocytic’. For it to be ‘megaloblastic’ there had to be a hypersegmented neutrophil. +

+1
submitted by ∗krewfoo99(114),

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lifoc icad ewnh it eertsn eth ybod is ni the romf of tyhttlfdtymraleeharooe HTF( athete)md.ly tI tnesdoa tsi ylhemt gpruo ot mtaiinv 1B2 to ceebmo HTF eht( ativec mofr wihhc sa a DAN pos.rrr)euc h eT iimtnva 21B thiw sti emhytl uopgr gseo on to ecnbiom wthi iochteymoen ot rmfo nenmhtoiie.

+1
submitted by ∗sunshinesweetheart(102),

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crcyctoaim aeimna (eens in lobdo sa)mre = CRB eossupcrrr cna gwro tub not dvidie

olva tyaosmcerc nee(s ni doobl )earsm = itacalsleobgm aimean (fi yeth t'ond hswo oituelpnhr eprtg)iotnehnsemay

21B sha nilouorcge msmstypo nda low lhctlneaomiym acid eilwh elafot ciiyfdncee sdoe nto

etaflo si beodrsba ni njemu,ju B12 in emlui

sceau s of 1B2 eccyiifedn = siucrnopei enami,a cgytmtes,ora ealli ti,ercnose ifhs ta,ewprom v aisegnm

)D aufelri fo MTHRF ;g--t& FHT avi( mleftrensareyhtsa = B21 dnecfiyice dan mrcaoyctic iaanem

)B DGP6 deniyifcec = ocnryotcim ubaeces fo cnir RBC tdi;rustocne tp udwol ohws sanulrriatvac soymsiehl sx tiietepdarcp yb na xaievtdio rrtseoss

C) ionoorptrgeonhypp adisxeo diyincefce = irtcocicmy aemani saueecb of low hmee sthnssiye

A) edrc rfanrtinser = hgih inetirrf = ienaam fo cchroni desisea = ocyitcrmci aimane aubcees of low orin

+1
submitted by ∗an1(92),

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sWa atbou ot csohoe dseedecra enfrsinatrr asebecu I cn'udtlo ees hee-edyensrtmgp lnrepsotihu. But EMBN nfteo eitsr to othrw us off with uvega esgai.m So I erad ag.nia uChtga eht l"eaIl ne"stc.oire Iorn tsFi r!Bo uIelm si 21B sntbr.iaoop B21 sslutre in bliemcoagalts e.mania HNMT-F5 si a tsep ni noecrvnigt HDF toin H.TF ntIiidbhe in tlclseboiamag menaia like 12B adn 9B fde.

an1 Also recall, that B12 is stored for many years. so presenting with a def years later (I agree 10 is a jump but still) is an indicator too +

+0
submitted by ∗unknown001(2),

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ohw ot elru tuo orin .fed ? n rio is debsrabo ni edoemnud dan omixaprl njumeju .

12b ni em.iul

stih lwli eivg yuo the warsne