Klinefelter's Syndrome

Explore The World of Extra Chromosomes


Klinefelter's Syndrome is when a male has an extra X chromosome putting their total chromosome count at 47. The symptoms include small testes which produce less testosterone, breast enlargement, delayed or incomplete puberty, reduced facial hair and body hair, and infertility. Many also experience learning disabilities and IQ's 10 to 15 points less than their siblings. Klinefelter's Syndrome affects 1 in 500 to 1,000 boys, with variants of more than 1 extra X chromosome affecting 1 in 50,000. Approximately 3,000 affected boys are born each year in the United States. Veronique Renard and Lili Elbe had Klinefelter's Syndrome and George Washington is speculated to have had it as well.
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How it works

Klinefelter's Syndrome is when a boy has an extra X chromosome. It is caused by a defective egg or sperm having an extra X chromosome. Since it is an extra X chromosome, it doesn't affect any proteins and is not caused by a mutation. Klinefelter's Syndrome does affect testosterone production though, with the affected male barely producing any if at all. Klinefelter's Syndrome is also not inherited. Every male has the same chance of having it.

Diagnosis and Treatment

Most doctors test for Klinefelter's Syndrome if a boy's testicles don't develop properly. Tests for boys include Chromosome Analysis (Karyotyping) and hormone testing. Prenatal tests can be done as well, but they are done less frequently. There is no real "cure" for Klinefelter's Syndrome, but there is still treatment. Testosterone injections can be used to develop the boy's body and speech therapy and educational support can help with the learning disabilities.

It is natural for parents to feel that they have done something wrong to cause Klinefelter's Syndrome, even though they have no control over it. Some try to force their child to act like a "real" boy and do what they, but some boys with Klinefelter's Syndrome have the mentality of a female, so this can be detrimental to their psyche. Parents should support their child's development by getting speech therapists and tutors to keep their son from falling behind. If parents have any concerns they should talk to their doctor.


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