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NBME 21 Answers

nbme21/Block 4/Question#15 (reveal difficulty score)
A 5-year-old boy is brought to the physician ...
Lack of choroidal pigment deposition in the macula 🔍 / 📺 / 🌳

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submitted by hungrybox(1170),
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tblmoutahe = hbtmuEtoaYEl

retGa mnomneic rfo mbeereirnmg taht mbtluoYEahEt si hte opnomcent ahtt sceuas sivlua emslrobp in EPRI payerht for T.B

submitted by henoch280(66),
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eym.t@m ihTs enosiuqt ttess ruo geelnowkd on aiinslbm hicwh si malolnry a irasneyost ydefcnieic edsesia tbu hte getientv ssetat htat het yb'so imsnlaib si ausedc by a genetic atnuimto in teh 1RPTY gene chhwi si onhsw in eht aihoclbicme hy.tpwaa A neeg that lhspe ni hte iseynssth fo Eulimnea.n

Nwo uoy have to adtesrnudn htta lal serusrproc rfobee atth egne si het awtyhpa dowlu litsl eb laaavblei if tno asierdcen hcwih mkea 2 fo hte sooptin ni eht oqtesiun g.rown

yuo also vhea ot dutrsadnen (imlnnt )uE:isahe = noenl)n(amirom .ei alrmno anlniem whhci is etvicreopt to teh kisn, eedescras eitaevcr yxogne speisec and gsvie eth rkda nespimtg to eht sri,i hrd,icoo kins, aihr e) ihmif.. nea.welotcn(le = ekennail)(amf .ei ieonlam,nhpe het oen rtnepse in our patnite heer whchi is less cvtteeroip agnia het uv s,ayr tnnoac nmetgip dan onncta eesdrcea ORS dteeenagr in hte snk i.i opeh isth eslhp

submitted by cantaloupe5(85),
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cesocPrs of iiinamnlote rof siht noe. oTw uyo can lenaitiem itmimedyeal tsuj fmor iolnkog ta het cabmliohcei ythawpa eTh hteor owt irdreqeu delwgkone tath neminaule si mroe cotvtrpeei tahn nmeehloinap htis( si why eadhserd unbr erom s) aeBescu moenpihalne si lses tpocvte,ier eehrt uwlod eb orem nto slse RSO frmo sgh.ntliu

temmy  i don't understand this at all. i am completely blank...please help +3  
henoch280  @temmy. This question tests our knowledge on albinism which is normally a tyrosinase deficiency disease but the vignette states that the boy's albinism is caused by a genetic mutation in the TYRP1 gene which is shown in the biochemical pathway. A gene that helps in the synthesis of Eumelanin. Now you have to understand that all precursors before that gene is the pathway would still be available if not increased which make 2 of the options in the question wrong. you also have to understand this: (Eu)melanin = (normo)melanin i.e normal melanin which is protective to the skin, decreases reactive oxygen species and gives the dark pigments to the iris, choroid, skin, hair e.t.c. while (feo)melanin = (fake)melanin i.e pheomelanin, the one present in our patient here which is less protective again the uv rays, cannot pigment and cannot decrease ROS generated in the skin. i hope this helps +31  
eacv  @henoch280 thank u very much! I got it right by luck but now i do understand :D +  

submitted by drfish(3),
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I veebeil shit eon aws stju na nesarw fo oxencsilu / cpsosre of .litaimnineo Yuo adh ot sndrudetna htat eth oecooteprtivtph mfor of inaemln si eht bcalk neo (nenumilae) dna pyoeialmnnht (de)r si sesl t.rtoecihtopepov Fmor etrhe it caislyabl si sgaiyn a mcetolpe sosl fo ucionftn ioumttan of 1TR.YP

  • eecbnsA of ssentryaoi i(hceco )A is stit—neasdmeirniyolea is ywa mrtapuse of T.1RYP

  • srdDeeeca rtsninoencctoa of ,56 hoecc(i B) is liadtneime cnies hteer wduol eb readescin tsrbauets fo .TPR1Y

  • aDedcerse SOR ohecc(i C) dna drensieca nootooirthpctep oc(cihe D) rae eltmedniia ecsbeua eterh si sles opepootithntocr mofr eth osls fo neaumenli = nasedecir ORS.

tnrplaypAe hcidoralo igenmpt si mdea fo aimtnhlpyeon tbu on ywa uoy erwe eexecptd ot wkon tht.a

submitted by sweetmed(150),
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Eliunnmea sloa plesh het rcdhoio mitli oelnocudnltr erilctoenf wintih the yee taht dlwuo nitllaytoep lersut in het pnepiteocr fo iocgsunfn aeigm

submitted by sahusema(155),
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I tcu peon an eylalbe ocen dan I asw rdpiserus how desen acklb het elamirat sneiid ws.a ahtT uspl operscs of tnianmleiio hbrtgou em ot hte trgih wseran

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