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 +0  (nbme20#46)

The key bit in this question that makes the answer Cholecalciferol rather than 7-dehydrocholesterol is the nugget that the patient "rigorously avoids exposure to the sun." Conversion of 7-dehydrocholesterol to Cholecalciferol can only occur when the skin is exposed to sunlight. Therefore, decreased production of Cholecalciferol (D3) is the better answer.

This picture always helps me remember Vitamin D metabolism.

 +0  (nbme21#9)

Whole point of administering a SERM after breast cancer is to reduce risk of recurrence. Increased estrogen exposure is associated with increased risk of breast cancer (per FA 2019 p. 636). So you're looking for something that is an estrogen antagonist at the breast, which narrows it down to B and C right off the bat.

Subcomments ...

submitted by haliburton(171),

ranitidine blocks H2 receptor, which is Gs. Gs activates adenylyl cyclase -> +cAMP.

q: HAVe 1 M&M => H1, alpha1, V1, M1, M3 i: MAD 2 => M2, alpha2, D2 s: (everything else) => beta1, beta2, V2, D1 H2

I think this is from FA.

baja_blast  Yes; FA2019 p. 238 +  

submitted by drmohandes(52),

Countertransference (FA2019 pg. 542) = doctor projects feelings about formative or other important persons onto patient (e.g. Epstein didn't kill himself).

baja_blast  They really had mercy here by not also including Transference as an option.... phew. +  

submitted by welpdedelp(154),

It was just asking the lifespan of RBCs (120 days)

haliburton  If I'm reading this right, this is just a tricky dicky question. I think CO binds 200x stronger than O2. But if an O2 cycles through binding / unbinding 200 times before a CO gets kicked off, this should still clear the CO from that cell sooner or later. strange to think it is 1. essentially permanently trapped in a cell, and 2. doesn't kill you and can be treated with O2 to resolution within a few hours or a day. They must just be thinking, until that last RBC dies, you've got original CO in a circulating cell. but just a fraction (because you didn't die). not sure how that CO isn't just passed on during recycling, based on this line of thinking. +5  
link981  The question while stupidly written, asks how long the RBC's that carry the CO take to be removed from the circulation, not how long the CO takes to be removed from the RBC. Just asking the lifespan of RBCs in an stupidly complicated way. As we know, RBC's life span is about 120 days and then they are removed from our circulation. 120 days is about 4 months. Next time they will probably ask weeks or in hours, who knows? smh +4  
baja_blast  If that's what they're looking for why cant the NBME people just ask "How long does it take for RBCs to turn over?" Ridiculous. +  

FA 2019 p156 Does anyone know how to differentiate the picture labeled Trypanosoma brucei and cruzi?

footballa  This question is likely not important for two reason: They're both Trypansomastigotes, so of course they look almost the same. You can differentiate these two species clinically as they have very little clinical similarity in patient presentation. For these reasons there's little to no reason you would be expected to differentiate these two species by histology alone +2  
snripper  Does Chagas have recurrent fever? Because that's what pointed me to African Sleeping Sickness. +  
baja_blast  The history of travel to the Amazon is what pointed me to Cruzi over Brucei but agree it's a tough distinction to make here. In the absence of that detail I would have probably picked Tsetse fly. +1  

submitted by armymed88(42),

Glucose is co-transported into enterocytes of SI via sodium

toxoplasmabartonella  That makes that glucose needs to be given with sodium. But, what about bicarb? Isn't the patient losing lots of bicarb from diarrhea? +3  
pg32  Had the same debate. I knew glucose/sodium was the textbook answer for rehydration but also was wondering if we just ignore the bicarb loss in diarrhea...? +2  
makinallkindzofgainz  @pg32 - Sure, they are losing bicarb in the diarrhea, and yes this can effect pH, but it doesn't matter that much. You're not going to replace the bicarb for simple diarrhea in a stable, but hydrated previously healthy 12 year old. You're gonna give him some oral rehydration with a glucose/sodium-containing beverage. Don't overthink the question :) +1  
makinallkindzofgainz  *dehydrated +  
teepot123  salt and sugar, that's all the kid needs when ill simple +  

submitted by seagull(838),

out of curiosity, how may people knew this? (dont be shy to say you did or didnt?)

My poverty education didn't ingrain this in me.

johnthurtjr  I did not +1  
nlkrueger  i did not lol +  
ht3  you're definitely not alone lol +  
yotsubato  no idea +  
yotsubato  And its not in FA, so fuck it IMO +1  
niboonsh  i didnt +  
imnotarobotbut  Nope +  
epr94  did not +  
link981  I guessed it because the names sounded similar :D +10  
d_holles  i did not +  
yb_26  I also guessed because both words start with "glu"))) +14  
impostersyndromel1000  same as person above me. also bc arginine carbamoyl phosphate and nag are all related through urea cycle. +  
jaxx  Not a clue. This was so random. +  
wolvarien  I did not +  
ls3076  no way +  
hyperfukus  no clue +  
mkreamy  this made me feel a lot better. also, no fucking clue +1  
amirmullick3  My immediate thought after reading this was "why would i know this and how does this make me a better doctor?" +5  
mrglass  Generally speaking Glutamine is often used to aminate things. Think brain nitrogen metabolism. You know that F-6-P isn't an amine, and that Glucosamine is, so Glutamine isn't an unrealistic guess. +2  
djtallahassee  yea, I mature 30k anki cards to see this bs +3  
taediggity  I literally shouted wtf in quiet library at this question. +1  
bend_nbme_over  Lol def didn't know it. Looks like I'm not going to be a competent doctor because I don't know the hexosamine pathway lol +1  
drschmoctor  Is it biochemistry? Then I do not know it. +2  
snoochi95  hell no brother +  
roro17  I didn’t +  
bodanese  I did not +  
hatethisshit  nope +  
jesusisking  I Ctrl+F'd glucosamine in FA and it's not even there lol +  
batmane  i definitely guessed, for some reason got it down to arginine and glutamine +1  
waterloo  Nope. +  
monique  I did not +  
issamd1221  didnt +  
baja_blast  Narrowed it down to Arginine and Glutamine figuring the Nitrogen would have to come from one of these two but of course I picked the wrong one. Classic. +  
amy  +1 no idea! +  

submitted by oznefu(10),

I get that the answer is correct for a reversible injury where there is cell swelling because of the increased intracellular Na+ and Ca2+ due to impaired Na/K and sarcoplasmic reticulum activity ...

But if there are increased cardiac enzymes in the blood indicating cell death and membrane damage, wouldn’t the intracellular electrolytes be low since they are released into the blood?

lord_voss  troponin = irreversible injury and membrane damage -> high extracellular concentration of Na+ and Ca++ causes both to move into cell through damaged membrane and high intracellular K+ leaves the cell +9  
rogeliogs  Question is asking about the changes in the myocardiocytes and my second interpretation was that they are asking the changes before they "rupture" and liberate their content in the blood producing increase enzymes in the patient. Therefore because is a ischemic process = reduction of O2 = low ATP = impairment of Na/K ATPase = increase Na-decrease K intracellular = block Ca/Na exchanger = increase Ca intracellular. the same effect as digoxin +2  
allodynia  What will happen to Na and ca conccentration when there is an irreversible injury? +  
baja_blast  @allodynia Pathoma pg. 4 has a really good summary of this. In short, Na+ and Ca2+ both increase intracellularly in an irreversible injury. +  

submitted by usmleuser007(278),

1) EBV = Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma, 1° CNS lymphoma (in immunocompromised patients)

2) HBV & HCV = Hepatocellular carcinoma

3)HHV-8 = Kaposi sarcoma

4) HPV= Cervical and penile/anal carcinoma (types 16, 18), head and neck cancer

5) H. pylori = Gastric adenocarcinoma and MALT lymphoma

6) HTLV-1 = Adult T-cell leukemia/lymphoma

7) Liver fluke (Clonorchis sinensis) = Cholangiocarcinoma

8) Schistosoma haematobium = Bladder cancer (squamous cell)

some0217710  Aren’t both H.pylori and EBV associated with gastric lymphoma? +3  
baja_blast  You're right that EBV is associated with gastric lymphomas, but this is specifically asking about marginal zone lymphoma (or MALToma) which is associated with H. Pylori, not EBV. https://www.ncbi.nlm.nih.gov/pubmed/11552717 +  

submitted by joha961(34),

Maintenance dose = (Css * CL * t) / F

... where t is elapsed time between doses (not relevant here since it’s continuous infusion) and F is bioavailability (which is 100% or 1.0 here because it’s given IV).

​Contrast with loading dose:

(Css * Vd) / F

... where Vd is volume of distribution.

yotsubato  So do we just have to memorize this... +6  
gh889  yep +9  
drschmoctor  @yotsubato Not necessarily. I can't remember a formula to save my life. The Css is the amount you want in the blood. The clearance is the fraction removed per unit time. Since we want to maintain a steady state, we only need to replace what is removed. Thus, maintenance dose = amount present * fraction removed. +4  
mambaforstep  https://www.youtube.com/watch?v=gnqOUmNhmdg good & short explanation +  
castlblack  I remember CLoCk Time as in check the clock time to give the next dose Cl = clearance, C = concentration and T = half life. I have never had to use F. +1  
baja_blast  This is on p. 233 in FA 2019. +  

Although there are no specific herpes indicators, a CSF panel with mostly leukocytes indicates a viral infection (as well as the normal glucose). So you can rule out TB, neurosarcoidosis and bacterial. Brudzinski/kernig sign are related to meningitis, but even if you don't know what those are, the question says that there is an abnormality in the TEMPORAL lobe (meningitis = meninges). Encephalitis would be the best answer, especially because Herpes Encephalitis affects the temporal lobe.

taediggity  Also look for Kluver-Bucy like symptoms in the stem +1  
mambaforstep  why? +  
b1ackcoffee  I agree with everything but normal glucose. Glucose here is NOT normal. to quote wiki "The glucose level in CSF is proportional to the blood glucose level and corresponds to 60-70% of the concentration in blood. Therefore, normal CSF glucose levels lie between 2.5 and 4.4 mmol/L (45–80 mg/dL)." +  
baja_blast  NBME reference table gives normal CSF glucose to be 40-70 mg/dL. As far as I'm concerned, for the purposes of the exam the reference table is probably a better source than wiki. +1  

submitted by bhangradoc(16),

The P-value is basically type 1 error, and they keep the p-value the same (at <.05) in both versions of the experiments. By increasing number of patients in the group, they increase power of the study, which reduces type II error.

jfny21  Thank you +1  
baja_blast  For more, FA 2019 p. 262 goes over Type I and II errors. +  

submitted by neonem(450),

Alcohol withdrawal leads to a sympathetic-hyperactivity-like syndrome with tremors, HTN, insomnia, GI upset, diaphoresis, and mild agitation 3-36 hours after the last drink. There is a similar, but usually slightly later, overlap of withdrawal seizures 6-48 hours after the last drink.

katsu  Alcohol withdrawal sx (p. 554 FA 2018) Time from last drink: 3–36 hr: tremors, insomnia, GI upset, diaphoresis, mild agitation 6–48 hr: withdrawal seizures 12–48 hr: alcoholic hallucinosis (usually visual) 48–96 hr: delirium tremens (DTs) Treatment: benzodiazepine +1  
baja_blast  p. 558 in FA 2019. +  

submitted by sympathetikey(752),

Direct Antiglobulin = Direct Coombs Test

Detects antibodies bound directly to RBCs. Hemolysis most likely due to something in the transfused blood (not sure why it took 4 weeks when Type 2 HS is supposed to be quicker but w/e).

ergogenic22  there is a delayed onset hemolytic transfusion reaction which should be evaluated with direct cooms test. https://www.ncbi.nlm.nih.gov/books/NBK448158/ +5  
hungrybox  such a dumb question wtf +16  
sonichedgehog  takess longer due to slow destruction by RES +  
baja_blast  Dang, I didn't know that was the same thing as a direct Coombs test. I guess it makes sense in hindsight. Thanks! +  

submitted by lilyo(33),

Take a look at FA pg.623 for tanner stages of sexual development.

baja_blast  (This is the right page for FA 2019) +  

submitted by hayayah(884),

Fanconi's is a generalized reabsorption defect in PCT causing increased excretion of amino acids, glucose, HCO3–, and PO43–, and all substances reabsorbed by the PCT.

baja_blast  FA2019 p. 581. Fanconi syndrome causes a type 2 (proximal) renal tubular acidosis +  

submitted by ankirin(2),

What is esophageal spasm and how would it present differently?

baja_blast  I had narrowed it down to that and the correct answer. I think the difference is that esophageal spasm tends to present with pain and dysphagia. FA 2019 p. 371, right at the top of the page. +  
orthonerd  Relating the phrase "diffuse painful contraction" to esophageal spasm has helped me remember the associated descriptions they go to. +  

submitted by hayayah(884),

In narcolepsy, there is a direct transition from wakefulness to REM sleep. Basically instead of going through the early stages and gradually falling into a deep sleep, you just suddenly go from being awake to being in a deep sleep.

kamilia20  FA2020 P497(Sleep physiology): Changes in narcolepsy: decrease REM latency. +1  
baja_blast  p. 485 for us plebs still using FA 2019 +  

submitted by divya(37),

Why is there rhinorrhea in opioid withdrawal? And also, if stimulants like cocaine cause nasal vasoconstriction, shouldn't opioid withdrawal do the same?

the_enigma28  Mechanism of opioid-induced rhinorrhoea, lacrimation, stomach cramps and diarrhoea is actually muscarinic receptor effects, rather than alpha adrenergic blockade caused by cocaine, causing nasal vasoconstriction. +1  
baja_blast  Symptoms of Opioid Withdrawal can be remembered with the phrase "anxious, hot, and moist" per SketchyPharm Opiods. Rhinorrhea is one way people can be "moist" during opioid withdrawal, but they can also sweat excessively and lacrimate too. +1  

submitted by tinydoc(157),

Neuropathic Pain after stroke is central Post stroke pain Syndrome

caused by contralateral thalamic lesions

Pg. 504 FA19

chandlerbas  agreed! more specifically damage to the VPL +3  
docshrek  Pg. 403 FA 19. +  
baja_blast  Both commenters above got the page wrong; it's FA 2019 p. 503. +1  
teepot123  looooool ^ what were the odd of both being wrong +  

submitted by est88(15),

Pyruvate Kinase defect leads to decreased ATP leading to rigid RBCs and extra vascular hydrolysis. Increased levels of 2,3-BPG decreases hemoglobin affinity for O2.

baja_blast  FA 2019 pg 414 +  

submitted by temmy(92),

please help according to winters equation the patient has a normal anion gap

ergogenic22  winter's formula is to look at the compensation to see if it is appropriate. PCO2 = 1.5[HCO3-] + 8 +/- 2 In this case, 1.5* 10 (Pt's bicarb) +8 +/-2 = 21 to 25 Pt's PO2 is 23, so compensation is appropriate. If PCO2 was below 21, it would be concomitant respiratory alkalosis +4  
ergogenic22  in other words, winter's formula is not necessary for this question +2  
the_sacramento_kings  lol unless you want to make sure its not A. +1  
hello  @ergogenic22 Someone might use Winter's formula to rule out choice A. +  
maxillarythirdmolar  respiratory depression of alcohol should rule out "A" +  
baja_blast  Isn't the low pCO2 enough to rule out A? +  

submitted by benzjonez(27),

FA 2018 p. 609. Suspect urethral injury if blood is seen at the urethral meatus. Mechanism of posterior urethral injury = pelvic fracture, which we see in this patient. Urethral catheterization is relatively contraindicated.

hyperfukus  thank you! +  
baja_blast  Understood, but is there anything in the question that rules out BPH specifically? I honed in on the words "most likely" and saw he was 60. I guess I overthought it but I'd appreciate any insight as to what if anything in the Q makes that definitively wrong. +  
daddyusmle  I think the question stem, with the trauma and fractures, points you in the direction of membranous urethral trauma. Pelvic fractures are more associated with urethra damage than prostate damage, although they're right next to each other, and I can see why someone would choose prostate hypertrophy. Also, I'm not sure if bleeding is associated with BPH. +  

submitted by hyoscyamine(47),

FA pg.372. Squamous cell carcinoma occurs in the upper 2/3 of esophagus whereas adenocarcinoma occurs in the distal 1/3. Since this was in the mid esophagus, its squamous cell carcinoma. Key feature of squamous cell carcinoma is keratin pearls.

turtlepenlight  can remember it as wearing a pearl necklace (upper 2/3 of throat-ish) +3  
baja_blast  Patient is also a heavy smoker and drinker. In the absence of GERD this should raise suspicion for SCC of esophagus over Adenocarcinoma. +  

submitted by thotcandy(20),

What is there that rules out deltoid? overhead abduction is >15' so shouldn't that point more towards deltoid?

baja_blast  Deltoid only does abduction from 15 to 90 degrees. So not overhead. +  
donttrustmyanswers  With that logic, supraspinatus only does abduction form 0-15 +3  
rina  the positive empty can test is the biggest thing "pain and weakness with abduction, particularly with simultaneous shoulder internal rotation" - that tells you it has to be one of the SITS muscles (supraspinatus, infraspinatus, teres minor, subscapularis), not the deltoid. tenderness in the right deltoid region tells you it's the supraspinatus which is right underneath the deltoid muscle +1  

submitted by krewfoo99(57),

Epinephrine acts mostly on Beta receptors. Beta receptors are G coupled.

baja_blast  Alpha receptors are also G-coupled and are another potential site of action for Epinephrine (at high doses according to SketchyPharm Sympathomimetics) +  

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