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NBME 20 Answers

nbme20/Block 3/Question#39

A 19-year-old woman has severe refractory pustular ...

Teratogenic effects in the embryo

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 +5  upvote downvote
submitted by mbourne(6),

This is a mish-mash of information I can find on this subject. Can't find good info on this anywhere. I think this question sucks

"Isotretinoin has a low affinity for retinoic acid receptors (RAR) and retinoid X receptors (RXR), but may be converted intracellularly to metabolites that act as agonists of RAR and RXR nuclear receptors.

In the nucleus of a cell, retinoic acid acts as a ligand, which is a molecule that binds to a site on a specific protein, to activate two families of transcriptional factors. These two families are the retinoic acid receptors (RAR) and retinoid X receptors (RXR), which bind to genes that respond to retinoic acid. There are three forms of RARs and three forms of RXR.

Studies with in vitro rat embryos have shown that retinoids act directly on the embryo, causing those embryo to develop abnormally."

euchromatin69  u world 1568 flow chart +  




 +2  upvote downvote
submitted by hayayah(508),

Isotretinoin is used to treat severe cystic acne. It is a teratogen. Can cause multiple severe birth defects. Contraception is mandatory. RXR is a retinoid X receptor.

IsoTERATinoin





the question was very poorly worded in my opinion, anybody else agree?

niboonsh  yea it was a dumbass question, whoever is writing these questions is undoubtedly a crazy genius but homeboy (or homegirl...homeperson?) needs a few grammar lessons. +1  
yex  I agree. We know that it is a teratogen, but how does that question directs you to think about teratogenic effects instead of something physiologic? +2  
dr_jan_itor  The questions in the NBMEs by default are reject questions. So highly selective to be awful questsions. I am recieving regular heads up that the stems on the real thing lately are like 10-12 lines long. So these questions are not anywhere near like the test. NBME has f'd us good for this particular round of practice forms. +  




 +0  upvote downvote
submitted by garima(1),

I think the question asks 'if it binds to RXR, what happens?'

The retinoid X receptor (RXR1) is an intriguing and essential member of the steroid/thyroid hormone superfamily of nuclear receptors (NRs) that predominately function as transcription factors with roles in development, cell differentiation, metabolism, and cell death

which means its related with development etc