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Klinefelter syndrome is a genetic disorder that affects males.
Normally, males have one X and one Y chromosome; males with Klinefelter
syndrome have at least two X chromosomes and, in rare cases, as many as three
Symptoms, when present, vary from one male to another depending on
the number of extra X chromosomes and how many cells in the body are affected.
Symptoms may include a lack of fully developed secondary male sexual
characteristics—such as the growth of the testicles and penis, deeper voice,
and body hair—by adulthood. These men usually cannot father children (are
infertile). Other symptoms may include delayed speech development, poor verbal
skills, below-average intelligence, or emotional and behavioral problems. Males
with more than one extra X chromosome generally have more severe
Klinefelter syndrome usually goes undiagnosed until the preteen
years (around ages 11 to 12), when males often begin puberty. In some males,
Klinefelter syndrome is never diagnosed and does not cause problems.
The main treatment for Klinefelter syndrome is hormone replacement
therapy to increase testosterone. Other treatments vary depending on the
symptoms and may include educational support for language and learning
difficulties and counseling or social skills training for behavior
Current as of:
March 12, 2014
John Pope, MD - Pediatrics & Stephen LaFranchi, MD - Pediatrics, Pediatric Endocrinology
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