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About Klinefelter Syndrome

Klinefelter Syndrome (KS) is a condition that occurs in men who have

one or more extra X chromosomes 

The syndrome can affect boys and men at different stages of life and their

physical, language, and social development.

The only symptom we all share is one or more extra X chromosomes. The most common symptom is infertility.  Boys may be
taller than other boys their age, with more fat around the belly. After puberty, boys/teens who have Klinefelter Syndrome may have:

Smaller testes and penis

Breast growth


Less facial and body hair


Reduced muscle tone


Narrower shoulders and broader hips


Weaker bones


Decreased sexual interest


Lower energy





We may have learning or language problems. We may be quiet and shy and need help fitting in.

A genetic test called a karyotype can definitively diagnose XXY/Klinefelter Syndrome.

There is no cure, but treatments are available.

Starting treatment as early as possible during our teenage years is essential.

With treatment and early onset, most of us grow up to have successful lives.

Treatments include testosterone replacement therapy, breast reduction surgery, and, If needed,

physical therapy, speech therapy, language development, and occupational therapy may also help.

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