Klinefelter Syndrome »
What is Klinefelter syndrome?
Klinefelter syndrome, also known as the XXY condition, is a term used to
describe males who have an extra X chromosome in most of their cells. Instead of
having the usual XY chromosome pattern that most males have, these men have an
XXY pattern. Klinefelter syndrome is named after Dr. Henry Klinefelter, who
first described a group of symptoms found in some men with the extra X
chromosome. Even though all men with Klinefelter syndrome have the extra X
chromosome, not every XXY male has all of those symptoms.
Because not every male with an XXY pattern has all the symptoms of
Klinefelter syndrome, it is common to use the term XXY male to describe these
men, or XXY condition to describe the symptoms.
Scientists believe the XXY condition is one of the most common chromosome
abnormalities in humans. About one of every 500 males has an extra X chromosome,
but many don't have any symptoms.
What...
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