XXYY syndrome
48,XXYY
Also known as: 48 XXYY
48,XXYY has two extra sex chromosomes, one X and one Y, added to a male complement. It shares features with Klinefelter syndrome, including tall stature and infertility, often with additional neurodevelopmental and behavioral features.
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What the notation means
48- total chromosome count (normal is 46)
XXYY- sex chromosomes: two X + two Y
Clinical notes
Klinefelter syndrome (47,XXY and variants)
An extra X in a male (≥1 Y with ≥2 X); 47,XXY is classic, with 48,XXXY and 48,XXYY as higher-grade variants. Tall stature, small firm testes, gynecomastia, infertility, low testosterone. The extra X (or Xs) inactivate as Barr bodies.