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 +0  (nbme21#12)

NBME/Uworld love to test renal artery stenosis in the setting of hypertensive urgency/emergency. Just because this has been done so many times, you can basically get the right answer from the first half of the question. Pt with end organ issues (headache, confusion) and really high BP (I know it isn't 180/120, but it is really high). So this guy basically has hypertensive emergency. I'm already thinking it's renal artery stenosis. Next sentence? A bruit over the left abdomen. Bingo. Renal artery stenosis, most often caused by atherosclerosis in older men (as compared to fibromuscular dysplasia in younger women).


 +0  (nbme20#48)

Can anyone explain why the lipase concentration is so high if there is an issue with LPL in hyperchylomicronemia?

garima  due to pancreatitis

 +1  (nbme24#30)

The fact that the odds ratio in the top left is incorrect makes this question very difficult. It makes it appear as if the cookies are causative but the milk had some protective factor. So obnoxious.

drpatinoire  God I thought totally the same way as you did. I stared at this question for at least 5min and asked myself what's wrong with my statistics.




Subcomments ...

submitted by liltr(13),

I choose MVP too, but this patient’s main symptom is cough only during exercise. This is more indicative of exercised associated asthma. You could see shortness of breath in MVP during exercise, but choosing MVP leaves the cough unaccounted for.

.ooo.   I agree! Also, At the end of the stem, the question is which of the following best explain the patients symptoms? Not physical exam findings. Since this patient is coming in with a chief complaint of SOB while playing sports exercise induced asthma is the best choice. Hopefully that helps. +7  
uslme123  I mean... couldn't increased BP during exercise worsen his MVP and give him SOB? +  
uslme123  (by causing slight regurg) +1  
yotsubato  "Lungs are clear to auscultation" +3  
sahusema  But wouldn't choosing exercise-induced asthma leave the murmur unaccounted for? +  
cienfuegos  I incorrectly chose malingering and am wondering if the fact that he presented (although it doesn't state who brought him in/confirmed his symptoms while exercising) makes this less likely despite the fact that he clearly states "I don't want to play anymore" which could be interpreted as a secondary gain? Also, regarding the MVP, I'm wondering if the fact that these are usually benign should have factored into our decision to rule it out? Thoughts? +1  
cienfuegos  Just noticed that he has FHx, game changer. +  
kimcharito  clear lungs, they try to say no cardiogenic Pulm. edema, means is not due to MVP shortness of breath while doing sports and no shortness at rest makes me to think more asthma induced by exercise) +  
pg32  Isn't exercise induced asthma usually found in people running outside, especially in cold weather? I feel like that is how it is always presented in NBME questions, so this threw me off. Not to mention the MVP. +  


submitted by yo(28),

I just knew that sperm need fructose, not sure what disease process this is though. He was pretty normal so 5a reducatase doesn't present like that. I wasn't sure if there was any odd use of the other answers. here is a link. Feel free to expand.

https://www.labce.com/spg27422_question.aspx

Fructose makes up 99% of the reducing sugar present in semen. This sugar is produced in the seminal vesicles. Diminished levels of fructose have been shown to parallel androgen deficiency and the testosterone level. Following testosterone therapy, the level of fructose increases. Although the fructose test is not part of a routine semen analysis, it is useful in cases of azoospermia (absence of sperm in semen). In azoospermia secondary to the absence of vesicles or if there is an obstruction, no fructose is present. In testicular azoospermia, fructose is present. When azoospermia and low semen volume exists, the fructose test should also be done, on a postejaculate urine sample to check for retrograde ejaculation. This occurs when the ejaculate goes into the bladder instead of out the urethra. The procedure for determining the amount of fructose in semen involves heating semen in a strong acid in the presence of resorcinol. Fructose gives a red color (Selivonoff reaction) and may be read in a photometer. The normal average is 315mg/dL fructose.

sam.l  Thank you for the explanation. I'm still confused about this answer. I was in between Zinc and fructose. Zinc deficiency also presents with anosmia (pg 71 First Aid 2019). Fructose is used for the movement. His hormones are normal. +1  
d_holles  Apparently diabetes, occlusion, and inflammation can result in ↓ fructose in sperm. Mauss et al, Fert Stert 25, 1974 https://www.fertstert.org/article/S0015-0282(16)40391-2/pdf +1  
cienfuegos  Thanks all for the info, quick note on the Zinc reply above @Sam.I: anosmia = lost sense of smell. +  
sam1  Great find yo! I believe this question was alluding to cystic fibrosis and the congenital absence of the vas deferens. Here is a link to a NEJM article about it below: https://www.nejm.org/doi/full/10.1056/NEJM196807112790203 +  
burak  zinc deficiency cause hypogonadism. there is no hypogonadism, sperms are damaged? +  
fatboyslim  @Sam1 but cystic fibrosis will show abnormal physical findings (clubbing, pulmonary crackles etc). The question says physical exam shows no abnormalities. +  
pg32  Confused as to how we can rule out zinc... From medicalnewstoday.com: "Zinc also plays a role in healthy sperm production. According to a 2018 review article in the Journal of Reproduction and Infertility, zinc deficiency may contribute to poor semen quality and infertility." +  


submitted by hungrybox(308),

Dysplastic nevi are a precursor to melanoma. They have irregular, "dysplastic" borders. Remember the "B" in ABCD stands for irregular Borders. Nevus means mole.

Other answers:

  • acanthosis nigricans - Darkening of skin associated with Type II diabetes mellitus

  • basal cell carcinoma of skin - Rarely, if ever metastasizes. Commonly affects upper lip.

  • blue nevus - Blue-colored type of common mole. Benign.

  • pigmented seborrheic keratosis - "Stuck on" appearance. Mostly benign. Affects older people.

  • (Note - you usually see only one. If multiple seborrheic keratoses are seen, it indicates a GI malignancy - aka "Leser-Trélat sign)
usmleuser007  correction ~ BCC affects the lower lip more than the upper +  
sympathetikey  Pathoma says upper lip, good sir +9  
hungrybox  Yeah basal cell carcinoma actually affects the upper lip. Counterintuitive because it's "basal" which seems to go along with the lower lip. Here's another source (this website is fucking gold btw): https://step1.medbullets.com/oncology/121593/basal-cell-carcinoma-of-the-skin +3  
pg32  Can anyone explain how we can rule out C or E purely based on the question stem? If we read into the question that we are looking for something related to melanoma, then I get why we can rule out C and E. However, the question simply asks which lesion appears on both sun-exposed and nonsun-exposed areas of the patient's skin. I would say that C, D and E can all occur in that distribution pattern. +  


submitted by hayayah(508),

the majority of carbon dioxide molecules are carried as part of the bicarbonate buffer system. In this system, carbon dioxide diffuses into the RBCs. Carbonic anhydrase (CA) within RBCs quickly converts the carbon dioxide into carbonic acid (H2CO3). Carbonic acid is an unstable intermediate molecule that immediately dissociates into bicarbonate ions (HCO3-) and hydrogen (H+) ions.

The newly synthesized bicarbonate ion is transported out of the RBC into the plasma in exchange for a chloride ion (Cl−); this is called the chloride shift. When the blood reaches the lungs, the bicarbonate ion is transported back into the RBC in exchange for the chloride ion. The H+ ion dissociates from the hemoglobin and binds to the bicarbonate ion. This produces the carbonic acid intermediate, which is converted back into carbon dioxide through the enzymatic action of CA. The carbon dioxide produced is expelled through the lungs during exhalation.

hungrybox  Amazing explanation. Thank you!! +  
namira  in case anyone wants to visualize things... https://o.quizlet.com/V6hf-2fgWeaWYu1u23fryQ.png +3  
ergogenic22  CO2 is carried in the blood is bound to hemoglobin, known as carbaminohemoglobin (HbCO2) (5%), dissolved CO2 (5%), bicarb is 90% +1  
pg32  Nice explanation, but can anyone clarify how we know from the question that we are measuring HCO3 rather than dissolved CO2? +  


submitted by nosancuck(44),

This b has Sarcoidosis so her granulomas be activatin dat VitD

sbryant6  Your mom activates my VitD. +3  
pg32  Anyone know why there is hepatosplenomegaly? +  


submitted by celeste(43),

The constellation of symptoms sounds like tuberous sclerosis. Cardiac rhabdomyoma is a rare benign tumor that is frequently associated with tuberous sclerosis.

tinydoc  Cardiac Tumors in adults -- usually myxoma Cardiac tumors in kids -- usually Rhabdomyoma ( ass. w/ Tuberous Sclerosis. ) --> its in the first aid rapid Review +3  
tinydoc  Cardiac Tumors in adults -- usually myxoma Cardiac tumors in kids -- usually Rhabdomyoma ( ass. w/ Tuberous Sclerosis. ) --> its in the first aid rapid Review +2  
arlenieeweenie  He also has seizures and pink-yellow papules, which I think they're trying to describe one of the characteristic ash-leaf or shagreen patches (doesn't sound like either of them to me lol) but that all points to tuberous sclerosis +  
pg32  @arlenieeweenie I think they are actually trying to describe angiofibromas that appear on the face in tuberous sclerosis, though I still think their description is pretty bad haha +  


submitted by nosancuck(44),

Yo dawg we all about PVT TIM HaLL

Phenylalanine, Valine, TryptoDANK, Threonine, Isoleucine, Methionine, Histidine, Leucine Lysine

meningitis  I don't understand what the question is asking... can someone please explain it to me? Patient doesnt eat protein, shes chubby. What does methionine have to do with this? +2  
charcot_bouchard  Just basically asking which is essential amino acids. +1  
usmleuser007  Essential amino acids (something i came up with) 1. "Three HAL fans will try meth" a. Threonine = Three b. Histidine; Arginine; Lysine = HAL c. Phenylalanine = fans d. Valine; Isoleucine; Leucine = will e. Tryptophan = try f. Methionine = meth +2  
nala_ula  They're saying there is a lack of good quality protein -> slight nutritional deficiency. She may have acquired weight but it's not because of protein. So they're specifically asking what amino acid she might be missing due to her subpar diet. Since essential amino acids are those that the body cannot make itself, out off those listed, methionine is the essential amino acid. It's on page 81 of FA 2019. +8  
nala_ula  correct me if I'm wrong please :) +  
hello  For anyone confused trying to follow @usmleuser007's comment -- slightly modified Essential amino acids mnemonic "Ah, Three fans will try meth" Ah = arginine, histidine Three = Threonine Fans (phans)= Phenylalanine Vil (Will -- German accent pronouncing English word 'will') = valine, isoleucine, leucine, lysine Try = tryptophan Meth = Methionine +1  
pg32  Why does @hello and @usmleuser007 mnemonic contain arginine? That isn't in the PVT TIM HaLL mnemonic for essential amino acids... +  


submitted by notadoctor(84),

Usual interstitial pneumonitis is the histological definition of Idiopathic pulmonary fibrosis. We know that this patient has pulmonary fibrosis because the question states that there is fibrous thickening of the alveolar septa. This question was just testing that we knew the other names for Pulmonary Fibrosis.

aneurysmclip  Nbme back at it again +4  
pg32  Is it still considered idiopathic pulmonary fibrosis is it appears to have been caused by an atypical pneumonia? +  


submitted by hungrybox(308),

Hydrochlorothiazide is a thiazide diuretic => thiazide diuretics are associated with hypokalemia.

What other diuretics are associated with hypokalemia? Loop diuretics.

Why?

Inhibition of Na+ reabsorption occurs in both loop diuretics (inhibit NKCC cotransporter) and thiazide diuretics (inhibit NaCl cortransporter). All of this increased Na+ increases Aldosterone activity.

Relevant to this problem, Aldosterone upregulates expression of the Na+/K+ ATP antiporter (reabsorb Na+ into body, expel K+ into lumen). This results in hypokalemia in the body.

Hang on, there's more high yield info!

Aldosterone does one other important thing - activation of a H+ channel that expels H+ into the lumen.

So, given that this patient has hypokalemia, you know there is upregulation of Aldosterone. Do you think her pH would be high, or low? Exactly, it would be high because inc. Aldosterone => inc. H+ expelled into the lumen => metabolic akalosis.

Now you understand why both loop diuretics and thiazide diuretics can cause what's called "hypokalemic metabolic alkalosis."

hungrybox  jesus this answer was probably too long i'm sorry +1  
meningitis  I disagree. It's the complete thought process needed for many Thiazide/Loop question that can be thrown. Thanks. +6  
amirmullick3  This is what NBME should be providing with each question's correct answer! Thanks hungrybox! +  
amirmullick3  @hungrybox did you mean "All of this DECREASED Na increases aldosterone activity."? +1  
pg32  Anyone care to explain why she feels she has, "lost [her] pep"? Is that due to the hypokalemia? Or hypercalcemia caused by the thiazides? +  


submitted by nuts4med(4),

I was thinking Chron’s because of the narrowing of the lumen and the picture seemed like there was creeping fat. Now that I think about it though, the LLQ and constipation should have led towards diverticulitis pretty quickly.

suckitnbme  Also agree the narrowing of the lumen plus the pic is pointing towards Crohn's. The acute systemic sx of fever and chills is what made me go with diverticulitis (along with the hx of increasing constipation). +  
pg32  Why does the question say there is NARROWING OF THE LUMEN? Does that happen in diverticulitis? I went with Chron's at the last second against my better judgment because Chron's can cause strictures/narrowing of the lumen. +  


submitted by hayayah(508),

Secondary hyperparathyroidism (usually d/t chronic renal failure).

Lab findings include ↑ PTH (response to low calcium), ↓ serum calcium (renal failure), ↑ serum phosphate (renal failure), and ↑ alkaline phosphatase (PTH activating osteoBlasts).

haliburton  also remember that in renal failure, 1-alpha-hydroxylase activity is down, so there will be less activation of 25-hydroxycholecalciferol to 1,25-hydroxycholecalciferol, which is a key mechanism causing hypocalcemia. +1  
cr  why not increased 25-hydroxycholecalciferol?, with the same logic haliburton explain +  
nala_ula  Increased phosphate, since the kidneys aren't working well, leads to the release of fibroblast growth factor 23 from bone, which decreases calcitriol production and decreased calcium absorption. The increase in phosphate and the decrease in calcium lead to secondary hyperparathyroidism. +1  
privatejoker  Probably a dumb question but how do we definitively know that the ALP is elevated if they give us no reference range in the lab values or Q stem? Everything stated above definitely makes sense from a physiological standpoint, I was just curious. +1  
fatboyslim  @cr the question asked "the patient's BONE PAIN is most likely caused by which of the following?" Increased levels of 25-hydroxycholecalciferol might exist in that patient, but it wouldn't cause bone pain. PTH causes bone pain because of bone resorption +  
suckitnbme  @privatejoker ALP is included in the standard lab values +  
makinallkindzofgainz  @privatejoker ALP is listed under "Phosphatase (alkaline), serum" in the lab values +  
pg32  Why does AlkPhos increase in renal osteodystrophy? The PTH would be trying to stimulate bone resorption (increase osteoCLAST activity), not bone formation (osteoBLAST activity). +  


submitted by monoloco(75),

This is a hypoplasia of the pleuroperitoneal membrane. The guts herniate into the thorax, usually on the left side, and result in hypoplasia of the lungs (because they're horribly compressed).

johnthurtjr  Usually on the left because the liver prevents herniation through the right hemidiaphragm +2  
asdfghjkl  aka congenital diaphragmatic hernia +1  
pg32  What's weird to me is that if you usually see air in the intestines on x-ray when they are in the abdomen, why is there no air in the thorax in CDH? The intestines should still have air in them, right? Also, what is filling the abdomen that causes it to appear grayed-out in CDH? +  


submitted by yotsubato(374),

"physicians should always encourage healthy minor-guardian communication."

Also you're going to do some serious things to cure this girl's disease, leading up to amputation. You cant hide that from her.

djjix  Non sense ... you can hide the amputation from her +6  
charcot_bouchard  Just show her one leg twice. +3  
pg32  I picked "request that an oncologist..." because I figured it would be better to have someone with more knowledge of next steps and prognosis discuss the disease with the family as compared to someone working in the ED... why is that wrong? +  


submitted by hayayah(508),

A big thing here too is noticing that the ALP is decreased. Osteoblast activity is measured by bone ALP. I think that was the main focus here and not that you necessarily need to know the CBFA1 gene mutation.

sympathetikey  Exactly. That's the only way I got to the answer. +  
pakimd  isnt increased alk phos consistent with increased osteoblastic activity? +  
champagnesupernova3  A defect with chondrocytes would cause an short limbs like in achondroplasia so those are ruled out +  
pg32  Exactly. Can also be helpful if you remember that the clavicles are formed by intramembranous ossification rather than endochondral; that allows you to rule out the chondroblast/cyte answer choices. +  


submitted by usmile1(26),

If you look at Uworld question ID 12299 it has a wonderful explanation for this. If they share the same epitopes, it will have a downward slope. If they share none of the same epitopes, the line will be horizontal across the graph (indicating no change as the amount of Y added increases)

eacv  omg YES!! thanks Uworld I got it correct! exactly this qx asked the exact opposite thing! Hahaha I loved it !! +4  
pg32  Even after reading the UWorld explanation, I am still not sure how the answer that reads, "Protein Y expresses all of the epitopes expressed by protein X, but protein X does not..." is incorrect. Based on the graph, I don't see a way we can rule out that answer choice and it sounds more likely than both X and Y having the EXACT SAME epitopes. Can anyone explain? What would the graph look like if the quoted answer choice was correct? +  


submitted by xxabi(123),

I was under the impression that this was an aortic dissection, due to "severe chest pain" as well as the false lumen in the aorta. And HTN is the #1 risk factor for aortic dissection. Someone correct me if i'm wrong, but I think this is aortic dissection rather than aortic aneurysm.

chefcurry  I believe so, FA 2018 pg 299 +2  
ergogenic22  It is dissection "extra lumen in the media of the proximal aorta" = "a longitudinal intimal (tunica intima) tear with dissection of blood through the media of the aortic wall" ... answer is still hypertension +  
breis  FA 2019: 301 +  
pg32  First Aid says that aortic dissection causes widening of the mediastinum and is due to an intimal tear, so I thought it wasn't an aortic dissection. Can anyone help me understand why First Aid was wrong in this case? Thanks! +  


submitted by nala_ula(48),

The histology is of spherocytes (small spherical cells w/o central pallor). Hereditary spherocytosis is due to defect in proteins interacting with RBC membrane skeleton and plasma membrane (ankyrin, band 3, protein 4.2, spectrin). Mostly autosomal dominant inheritance (so heterozygous mutation since you only need one mutant allele to get the disease).

wuagbe  To add to this: homozygous HS presents with hemolysis even in absence of stressors. this patient is only presenting with pale skin, and there are no schistocytes on the peripheral smear, so it's a heterozygous ankyrin mutation. +1  
pg32  I wanted to pick hereditary spherocytosis but the mean corpuscular concentration was normal and I thought it was supposed to be elevated? Also, why are there so many RBCs that are way bigger than the spherocytes? +2  


submitted by drdoom(263),

This is an interesting one. I like to remember it this way: in people with narcolepsy, all the “right kinds” of sleep are happening at all the “wrong times” of day. During the day, when a power nap would typically throw you immediately into REM, this kid is only entering Stage 1 or 2 (lightest sleep = slightest noises jar him back to reality). At night, when he should peacefully drift into Stage 1, 2, and so on, he instead completely zonks out. Classic narcolepsy.

From UpToDate: “Narcolepsy can be conceptualized as a disorder of sleep-wake control in which elements of sleep intrude into wakefulness and elements of wakefulness intrude into sleep.”

chextra  Isn't REM a rather light sleep stage? Brain waves during REM are very similar to awake states. I think you even wake up briefly in the middle of REM sleep. I don't think FA gave me a great understanding of narcolepsy, but I see it as going from awake to REM (light) for any kind of sleep, daytime or night time. +  
sammyj98  I'm definitely not ace on this subject, but I think the brain waves present in REM are similar to wakefulness because of the dreaming component. I think of it as though the brain has to go through a process of hypnotizing the body into a state of relaxation, and then properly paralyzing it, and then it can simulate wakefulness (dreaming) to go through with it's defragging of the hard drive. So REM is actually the deepest sleep because the body is fully paralyzed. Please someone correct me, this is probably an inacurrate perspective. +1  
pg32  FA says that narcolepsy has nocturnal AND NARCOLEPTIC sleep episodes that start with REM sleep... So is @drdoom correct? FA seems to disagree regarding the daytime sleep pattern. +  


submitted by hayayah(508),

Earliest detectable secondary sexual characteristic is breast bud development in girls, testicular enlargement in boys.

pg32  How did you know this? The Tanner stages in FA simply list pubarche and breast buds developing in the same stage without stating which comes first. Thanks! +  


I do understand that the principal nucleus of the trigeminal nerve is located at the pons. But since this patient is having trigeminal neuralgia wouldn't you be disrupting the pathway involved in pain and temperature, which in this case would be the spinal nucleus (located in the medulla)?

Besides, I found this at an article

A recent hypothesis attributes the pain of trigeminal neuralgia to a central mechanism involving the pars oralis of the spinal trigeminal nucleus.[5]

https://www.ncbi.nlm.nih.gov/books/NBK539729/

pg32  I literally had medulla selected the whole time and then changed it to pons simply because i felt the test writers were just seeing if we knew where the trigeminal nerve was located. bummer because I think your logic is way better. it's what i first thought when i read the case. +