NBME 21 Androgen insensitivity syndrome (NBME Answers)

Retired NBME 21 Answers

nbme21/Block 1/Question#6 (reveal difficulty score)
A normal-appearing 17-year-old girl has never ...
Androgen insensitivity syndrome 🔍 / 📺 / 🌳 / 📖
tags: repro repeat

+19 upvote downvote
submitted by ∗ergogenic22(401)

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chromatin negative = no barr bodies = person with XY genotype or XO because anytime you have more than one X chromosome you have a barr body (chromatin positive)

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+7 upvote downvote
submitted by ∗basic_pathology(25)

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Chromatin negative = no barr body. Could occur in Turner (XO) or male (XY).

Turner (XO):

streak ovarys
okay mullerian structures (most of the time)
okay female external genitalia

Androgen Insensitivity Syndrome (XY):

abdominal testes
no mullerian structures (SRY gene --> Testis --> Sertoli cells --> MIH) = Blind Pouch
female external genitalia (no Test/DHT signalling)

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+4 upvote downvote
submitted by ∗hyperfukus(111)

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Also another key is it says normal appearing girl one of the things about the AIS is that they do get secondary sexual characteristics...turner girls don't look normal they'd be short and stubby no boobs fat neck etc

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covid2019 I'm confused that they said she appeared "normal". I thought AIS would mean the patient has very scant pubic hair / underarm hair. Wouldn't this be abnormal in a 17 year old? Should have Tanner stage 5 hair.... +2

mumenrider4ever FA2020 (pg. 639) describes AIS as "Defect in androgen receptor resulting in normal-appearing female (46,XY DSD)" so I assume they're talking about general outwards appearance +2

lola915 You do get breasts because patient has build up of testosterone that is aromatized into estrogen. No axillary or pubic hair because that requires testosterone. +2

lovebug THX. SEE AIS (FA19 pg,625) +1

+1 upvote downvote
submitted by nerdy nik(9)

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Turner syndrome-> The girl would have a uterus and streak ovaries.

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+1 upvote downvote
submitted by ∗soph(84)

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all the other options pt would have uterus, ovaries. turners they wouldnt look normal and they would have atrophic ovaries.

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turtlepenlight This makes sense, but I was thrown off by the "normal-appearing" b/c wouldn't AIS pts not have pubic hair? +1

drzed They just say it's a normal appearing 17 year old girl; not that the external genitalia are normal appearing. +2

teepot123 fa 19 pg 625 +1

macroorchidism Yeah the "normal" look was referring strictly to appearance (body + genitalia) not secondary characteristics. I was also between AIS and Turner (because I didn't know chromatin-negative meant at the time), so another thing that helped me was I recently found that Turner syndrome patients are actually NOT completely infertile (they have like a 2% chance to fertilize). That helps me remember the internal female structures are there, I just picture them more as "empty." +1

-12 upvote downvote
submitted by ∗nosancuck(102)

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Yo dis B got NO INTERNAL FEMALE ORGANS

Why dat!???

We be lookin at someone with an SRY from dere Y chromie! Dey be a Y chromie Homie so they be makin some Testis Determinin Factor which I be sure makes some nice lil ANTI MULLERIAN FACTOR so dey aint got that Female Internal Tract u know what i be sayin

And since wimminz is da DEFAULT they stil be gettin dose pussy lips and breastes

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meningitis The above explanation is correct (disregarding the hard to read and unprofessional dialect) but just in case anyone was wondering: chromatin-negative= Just a quick way of knowing it was a boy. The term applies to the nuclei of cells in normal males as well as those in individuals with certain chromosomal abnormalities +17

yotsubato Turner syndrome patients are also chromatin negative as well though.... +6

sympathetikey I didn't know a complication post-meningitis was lack of humor. +6

sympathetikey Ah, didn't read the last line. Yeah, that is taking it a bit far +32

niboonsh yall are haters. this is the first explanation that has ever made sense to me +7

arkmoses https://www.youtube.com/watch?v=yuXL-3eoB-o&t=77s Interesting syndrome watching this helped me to put it into real life perspective, interesting points they have no pubic hair/body hair, they apparently also dont smell, and breast size is usually increased... +2

whoissaad How does chormatin-negative indicate a normal cell? Isn't chormatin just condensed DNA? +2

cienfuegos According to this paper most individuals with Turner Syndrome are chromatin negative: "One of the initial laboratory procedures used to confirm or rule out this diagnosis involves a sex chromatin determination from a buccal smear. Cells from the lining of the mouth are stained for the presence or absence of X-chromatin or Barr bodies, which represent a portion of an inactivated X chromosome. The typical Turner’s syndrome patient, who has 45 chromosomes and only one sex chromosome (an X), has no Barr bodies and is, therefore, X-chromatin negative. This abnormal X-chromatin negative finding in the majority of Turner’s syndrome females is similar to the result found in a normal male, who also has only one X chromosome, and differs from the X-chromatin positive condition observed in the normal female, who has two X chromosomes. Occasionally, the patient with features of Turner’s syndrome is found to be X-chromatin positive." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6233891/ +2

hyperfukus i really hate haters this is awesome! +2

selectuw to add to the above, free testosterone is aromatized to estrogen leading to breast development +1

misrao Is the free testosterone not creating male internal or external gentalia because of the defect in androgen receptors? +1

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