Official USMLE Facts/Concept Thread

[Shades McCool]

I think it would be good to post a concept or a fact that you picked up from a question bank that you feel is pretty high yield/important! This could be a very helpful thread if we all contribute.

I'll go first:
C. difficile causes damage to the gut by interfering with microtubles affecting epithelial cytoskeleton integrity.

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[rhino305]

When calculating an odds ratio or relative risk from a 2x2 table that's given to you in the question stem, make sure the table is set up correctly before you start plugging in numbers.

 

[Shades McCool]

That happened to me too. Such an easy point that just punches you in the nose and laughs at you.

Come on people, this has the potential to be a really helpful thread.

 

[WhoisJohnGalt]

By an unknown mechanism, beta blockers inhibit the peripheral conversion of T4 to T3.

 

[Shades McCool]

By an unknown mechanism, beta blockers inhibit the peripheral conversion of T4 to T3.

Did not know that, cool.

 

[HunterGatherer]

When calculating an odds ratio or relative risk from a 2x2 table that's given to you in the question stem, make sure the table is set up correctly before you start plugging in numbers.

was there an answer choice to reflect that?

 

[WhoisJohnGalt]

Did not know that, cool.

I didn't either, never saw it anywhere but UW.

 

[jjmack]

By an unknown mechanism, beta blockers inhibit the peripheral conversion of T4 to T3.

yes. they often use propranolol. I don't know if it's been proven to prevent the conversion, but does improve symptoms. I think only nonselective beta blockers work. good luck.

 

[WhoisJohnGalt]

yes. they often use propranolol. I don't know if it's been proven to prevent the conversion, but does improve symptoms. I think only nonselective beta blockers work. good luck.

UW's claim is that it definitely does inhibit the conversion.

I got curious and googled, and it would seem that it's backed up by the European Thyroid Association, Tufts, UCLA, eMedicine, and a few other reputable sites. I could make my evidenced-based medicine prof happy and do a "real" literature search, but I think I'm satisfied

 

[rhino305]

If we're going for minutiae (I think this is minutiae at least)

Isoniazid must be activated inside the mycobacterium by a catalase-peroxidase enzyme. Lower levels of this enzyme confer INH resistance.

 

[G0S2]

If you see a selective decrease in only RBC's and the bone marrow is not producing erythroblasts but everything else, it can be due to either B19 (not in the answer choices damn it) or a THYMOMA!!! (UW) Mechanism???


That was a smack in the face for me.

 

[G0S2]

By an unknown mechanism, beta blockers inhibit the peripheral conversion of T4 to T3.

Our pharm professor learned us this, yes, he sure did.

 

[domer621]

Our pharm professor learned us this, yes, he sure did.

Just propranolol, right?





Man with Strep pneumo coughing up green sputum... why is the sputum green?


Myeloperoxidase! (another UW fun fact)

 

[UCLAstudent]

Man with Strep pneumo coughing up green sputum... why is the sputum green?


Myeloperoxidase! (another UW fun fact)

I got this question a few hours ago! And I had a SECOND question on myeloperoxidase during the same session, which will be my tidbit: the Auer rods seen in AML are made of crystalized myeloperoxidase.

 

[cubsrule4e]

Drug-induced lupus: Procainamide, Quinidine, Hydralazine

 

[UT_mikie]

A patient presents with orange pigmented skin without scleral involvement or abdominal pain. What is the most appropriate question to ask next?

Do you eat alot of carrots? (Excess beta carotene can make your skin turn yellow but spares the sclera, in jaundice the sclera are typically involved)

Evidently this showed up on someones real exam. I don't know if this is common knowledge or not but it blew my mind.

 

[blz]

If you see a selective decrease in only RBC's and the bone marrow is not producing erythroblasts but everything else, it can be due to either B19 (not in the answer choices damn it) or a THYMOMA!!! (UW) Mechanism???


That was a smack in the face for me.

It's just an association with Thymoma, not a direct pathological consequence of it. Well atleast that's what Goljan says. It also can be associated with hypogammaglobulinemia. Dumb thymomas and their weird associations. It is probably only really worthwhile to know it's association with myasthenia gravis.

 

[myershurt]

this is slowly going to become a list of all UW questions with fewer than 30% correct responses...

 

[joe6102]

Drug-induced lupus: Procainamide, Quinidine, Hydralazine

I've never heard of that for quinidine. Pick procainamide if both are there, because they'll probably ask cinchonism for quinidine.

 

[71263]

It's just an association with Thymoma, not a direct pathological consequence of it. Well atleast that's what Goljan says. It also can be associated with hypogammaglobulinemia. Dumb thymomas and their weird associations. It is probably only really worthwhile to know it's association with myasthenia gravis.

I believe the association is with Lambert Eaton, an MG-like syndrome.

 

[71263]

Drug-induced lupus: Procainamide, Quinidine, Hydralazine

Just remember, its HIPPP to have lupus: hydralazine, Isoniazid, Procainamide, Phenyltoin, Pencillamine (the last one was a surprise to me too, got it off Qbank).

 

[cubsrule4e]

I believe the association is with Lambert Eaton, an MG-like syndrome.

Im not sure about Lambert Eaton but thymoma is definitely associated with MG (1 in 10 will have one)

 

[blz]

Im not sure about Lambert Eaton but thymoma is definitely associated with MG (1 in 10 will have one)

It's both.

Lambert-Eaton syndrome is against the presynaptic Ca2+ channels, Myasthenia gravis is against the Ach receptors. I think Lambert-Eaton is a lot more rare though. Both are gonna present the same, so I don't think it's a big deal. They'd probably ask Lambert-Eaton more in the context of small cell carcinoma since it'd be pretty obv there.

 

[DocMizzle]

It's both.

Lambert-Eaton syndrome is against the presynaptic Ca2+ channels, Myasthenia gravis is against the Ach receptors. I think Lambert-Eaton is a lot more rare though. Both are gonna present the same, so I don't think it's a big deal. They'd probably ask Lambert-Eaton more in the context of small cell carcinoma since it'd be pretty obv there.

There is an important difference in presentation. For L-E, weakness gets better with repetitive use due to buildup of presynaptic Ca2+, whereas in MG weakness gets worse with repetitive use.

 

[myershurt]

Just remember, its HIPPP to have lupus: hydralazine, Isoniazid, Procainamide, Phenyltoin, Pencillamine (the last one was a surprise to me too, got it off Qbank).

add an E - HIPPPE - for Ethosuxamide

 

[myershurt]

There is an important difference in presentation. For L-E, weakness gets better with repetitive use due to buildup of presynaptic Ca2+, whereas in MG weakness gets worse with repetitive use.

agreed - L-E pts. get stronger at the end of the day, where in MG, pts. get weaker...

 

[blz]

agreed - L-E pts. get stronger at the end of the day, where in MG, pts. get weaker...

good point

 

[domer621]

Yeah, the only similarity between MG and LE is the fact that they're both type II rxns acting at the NMJ...

 

[hyperorchidism]

some ones that got me

1) diptheria and pseudomonas bind E2F
2) Stills disease -> juvenile RA
3) toradol -> hematologic toxicity
4) capillary lacunar network originates from mother in placenta (kid -> villus)
5) swarming-> proteus, corkscrew-> trichomonas, falling leaf -> giardia, tumbling-> listeria
6) medial femoral circumflex -> avascular necrosis of femoral head
7) Sturge-Weber -> meningial angiomatosis, VHL -> cerebellar hemangioblastoma
8) CMZ floor of 4th ventricle
9) dermacentor - francisella, RMSF ixodes - babesiosis, anaplasma, Lymes
10) CD14/16 marker for myocbacteria giant cell
11) maternal diabetes --> transposition of great vessels
12) campylobacter -> gullain barre
13) VHL - ch 3, HUNTingtons - ch4, apc(POLYP) - ch 5
14) job syndrome --> macrophage probs with IFN --> cold abscess
15) heteroplasmy --> differing proportions of mitochondria in mito diseases
(leber optic neuropathy, myoclonic epilepsy w/ RRFs, MELAS)

...more to come

 

[blz]

i have a feeling a lot of people's averages are going to jump in usmleworld/qbank after reading this thread - lol

should be considered somewhat of a spoiler

but i think it's a good thread

 

[Shades McCool]

I don't know why but it always slips my mind that arsenic is associated with skin cancer. Nothing Earth-shattering I know, but it always slips my mind.

 

[71263]

i have a feeling a lot of people's averages are going to jump in usmleworld/qbank after reading this thread - lol

should be considered somewhat of a spoiler

but i think it's a good thread

Lets hope so. I guess its too late for me, as Ill be in the last leg of the exam at this time tomorrow... but hopefully someone else can benefit from this!

 

[blz]

I don't know why but it always slips my mind that arsenic is associated with skin cancer. Nothing Earth-shattering I know, but it always slips my mind.

also an association with angiosarcoma of the liver too right?

 

[71263]

also an association with angiosarcoma of the liver too right?

I thought that was polyvinyl chloride.

Quick fact: Arsenic acts by blocking Lipoic Acid. Symptoms include rice water stools and garlic breath.

 

[blz]

I thought that was polyvinyl chloride.

Quick fact: Arsenic acts by blocking Lipoic Acid. Symptoms include rice water stools and garlic breath.

it is polyvinylchloride too for angiosarcoma

im pretty sure arsenic too and another chemical that starts with "T"

lol i should just look this up.


EDIT: angiosarcoma of the liver ---> polyvinyl chloride, arsenic, and Thorium dioxide

 

[Shades McCool]

i have a feeling a lot of people's averages are going to jump in usmleworld/qbank after reading this thread - lol

should be considered somewhat of a spoiler

but i think it's a good thread

If it is a spoiler for a handful of questions on the real thing then I will be a happy man!

 

[domer621]

it is polyvinylchloride too for angiosarcoma

im pretty sure arsenic too and another chemical that starts with "T"

lol i should just look this up.

Thorotrast. Remember "VAT".

So much Goljan around here!

 

[Just Applied]

.

 

[blz]

Thorotrast. Remember "VAT".

So much Goljan around here!

lol remembering VAT would only remind me that it starts with a T, which I knew already, lol. I'm assuming Thorotrast or whatever is the same thing as thorium dioxide

 

[rhino305]

HIV+ mommy who refuses AZT even though she knows it decreases risk of infection to the fetus --> it's not illegal, and you can't make her

HIV+ mommy who just had baby and wants to breastfeed --> you can stop her by law

 

[hyperorchidism]

1) koilonychia -> iron deficiency, clubbing -> hypoxia, IBD, thyroid
2) ticlopidine used for aspirin/clopidogrel allergies but causes neutropenia
3) carbemazepine treats trigeminal neuralgia
4) bosentan -> ET receptor anatagonist
5) most common reason for aFP elevation --> dating error
6) bisphosphonates -> structural analogs of pyrophosphate in hydroxypatite, necrosis of jaw
7) clomiphene -> partial estrogen agonist in hypothalamus, works by preventing full feedback by estrogen to increase estrogen release
8) chlorpromazine --> corneal deposits, thioridazine --> retitinits pigmentosa
9) nitrate w/ 100% oral bioavailability -> isosorbide mononitrate
10) middle meningeal --> foramen spinosum
11) motor nuclei are medial, sensory lateral (trick does not work bad for most lateral medullary/medial medullary type syndromes though there is a lot of overlap)

 

[hyperorchidism]

HIV+ mommy who refuses AZT even though she knows it decreases risk of infection to the fetus --> it's not illegal, and you can't make her

HIV+ mommy who just had baby and wants to breastfeed --> you can stop her by law

these are good

 

[Shades McCool]

Polyarteritis nodosa - Hep B
Giant Cell Arteritis - Polymyalgia rheumatica

 

[cubsrule4e]

Christmas Disease = old name of Hemophilia B

for those still trying to go the extra mile: Named after Stephen Christmas, first person identified to have it

 

[cubsrule4e]

i think ill just let the responses pile up and then this weekend ill ditch FA and just use this thread to cram lol

 

[joe6102]

HNPCC = DNA repair gene
APC = tumor suppressor gene, prophylactic colectomy

 

[winsicle]

Christmas Disease = old name of Hemophilia B

for those still trying to go the extra mile: Named after Stephen Christmas, first person identified to have it

in keeping with this theme, Dr. Trousseau - "founder" of Trousseau's paraneoplastic migratory thrombophlebitis - later diagnosed pancreatic cancer in HIMSELF because HE had Trousseau's Syndrome

 

[rhino305]

did the same dr. trousseau have hypocalcemia and noticed his arm jerked when he had is blood pressure taken

or was that a different dr. t

 

[myershurt]

we all know the list of trinucleotide repeats - but -

non-familial polyposis is the only known DInucleotide repeat disease...

 

[Shades McCool]

we all know the list of trinucleotide repeats - but -

non-familial polyposis is the only known DInucleotide repeat disease...

Cash money!!