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Retired NBME 23 Answers

nbme23/Block 2/Question#36 (reveal difficulty score)
A newborn has external genitalia that appear ...
Hyperplastic fetal adrenal glands ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
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submitted by โˆ—maxillarythirdmolar(45)
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Likely an inhibition of 21-hydroxylase. This is the most common of the congenital adrenal hyperplasias. Presents in infancy or childhood.

Another symptom they may have that I've seen around is vomiting!! Took me a while to find it, but they are salt wasting by having no aldosterone, so the loss of electrolytes is causing increased ICP.

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fatboyslim  Nice! Thanks for the heads up +



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submitted by โˆ—avocadotoast(23)
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Boards and Beyond has a good flow chart for ambiguous genitalia. If the patient is XX - do they have mullerian structures? If yes, it's CAH (increased androgens). If they patient is XY - do they have mullerian structures? If yes, gonadal dysgenesis (no MIH). If no, then it could be due to abnormal androgen receptors, CAH, or low DHT.

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fatboyslim  CAH would only cause ambiguous genitalia in an XY if it's 17-alpha-hydroxylase deficiency because there would be no androgens. However, in the other enzyme deficiencies, an XY patient would be normal. DirtyMedicine has an AMAZING video and mnemonic to remember these: https://youtu.be/1vYmfz_LvjA +



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submitted by โˆ—wutuwantbruv(52)
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46,XX DSD due to excessive and inappropriate exposure to androgenic steroids during early gestation (i.e. congenital adrenal hyperplasia).

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jboud86  I'm just adding the page number from FA 2019 to this comment. FA 2019 page 625. +5
leaf_house  FA 2020 p 639 +
weirdmed51  leaf_house You arenโ€™t getting any votes until next year ๐Ÿ˜„ +



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submitted by โˆ—weirdmed51(30)
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Phenotype- male; genotype- female

I could think 2 causes 1. Placental aromatase defc 2. CAH (21 OH defc)

1 isnโ€™t an option.

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lulumomovicky  I thought the same ! And also, if 1 was an option, they could've mentioned that the mom got hirsutism or other changes due to elevated androgens during the pregnancy. +



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submitted by โˆ—cassdawg(1781)
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Just to add: gonadal dysgenesis is "defective development of the gonads in an embryo, with reproductive tissue replaced with functionless, fibrous tissue, termed streak gonads" per wiki. This is common in Turner's syndrome. External genetalia are typically normal at birth.

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submitted by โˆ—cassdawg(1781)
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Just to add: gonadal dysgenesis is "defective development of the gonads in an embryo, with reproductive tissue replaced with functionless, fibrous tissue, termed streak gonads" per wiki. This is common in Turner's syndrome. External genetalia are typically normal at birth.

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