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NBME 16 Answers

nbme16/Block 3/Question#1 (reveal difficulty score)
A 22-year-old man comes to the physician ...
46,XXY ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–

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 +9  upvote downvote
submitted by โˆ—cassdawg(1779)

This question can be answered by a process of elimination approach in my opinion: (FA2020 p638)

  • Because he has testes that formed, he has to have the SRY gene and thus the Y chromosome which eliminates 46,XX and 47,XXX.
  • This is not a normal-looking biopsy and the question asks about a chromosomal abnormality so you can eliminate 46,XY.
  • Mosaic karyotype 45,X/46,XY is associated with Turner's syndrome. These individuals present with female external genetalia and testes undescended or rarely descended into the labia majora. They would not have scrotal testes, and thus this eliminates this answer.

This leaves only 47,XXY which is Kleinfelter's syndrome and is associated with testicular atrophy and extensive fibrosis and hyalinization leading to infertility.

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i_hate_it_here  Kleinfelter's = fibrosed testis = decreased leydig and sertoli cells Turner's = fibrosed ovaries = decreased theca and granulosa cells +6
fatboyslim  ^Also, fibrosis of testes means there is a lot of collagen deposition (fibrosis), and collagen is pink on microscopy. A lot of pink = a lot of fibrosis +

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