NBME 21 Androgen insensitivity syndrome (NBME Answers)

NBME 21 Answers ↦

nbme21/Block 1/Question#6 (60.4 difficulty score)
A normal-appearing 17-year-old girl has never ...
Androgen insensitivity syndrome🔍
tags:

+16
submitted by ergogenic22(300),

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+4
submitted by hyperfukus(74),

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loAs tanhreo kye is it yssa anroml nraepagip rlig noe fo hte intsgh uaobt het IAS is htta tyhe od tge cnaydrseo suaxle iri.at.usrr.acscecttrhen glris od'nt look omlnar tey'dh be ohtsr and bbsyut on bboso fta cekn tce

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.... +

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 +1

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. +

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

+2
submitted by nerdy nik(10),

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eurTrn dn;tmose-yr&g The gril lwduo ahve a uerust adn kstrae ir.oaevs

+2
submitted by basic_pathology(8),

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)

+1
submitted by soph(54),

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all eth troeh spoiotn pt loduw evha eru,sut vsr.eioa tsuenrr yhte ulntwdo lkoo oranml nad yeht wlduo heav thrcioap .svreiao

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

drzed They just say it's a normal appearing 17 year old girl; not that the external genitalia are normal appearing. +1

teepot123 fa 19 pg 625 +

-12
submitted by nosancuck(85),

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oY ids B tgo ON TENANRIL EEMFAL OSGNRA

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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 +16

yotsubato Turner syndrome patients are also chromatin negative as well though.... +5

sympathetikey I didn't know a complication post-meningitis was lack of humor. +5

sympathetikey Ah, didn't read the last line. Yeah, that is taking it a bit far +20

niboonsh yall are haters. this is the first explanation that has ever made sense to me +5

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... +1

whoissaad How does chormatin-negative indicate a normal cell? Isn't chormatin just condensed DNA? +1

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/ +1

hyperfukus i really hate haters this is awesome! +1

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

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