What is XXY Syndrome?

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  • Written By: J.M. Willhite
  • Edited By: Heather Bailey
  • Last Modified Date: 13 August 2019
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When a male child is born with an additional X chromosome, he is said to have XXY syndrome. Also known as Klinefelter syndrome, this rare condition results from the presence of an inessential X chromosome that adversely impacts a male's testosterone production and sexual development. Treatment for XXY syndrome is often centered on testosterone replacement therapy, counseling, and may necessitate surgery. Long-term therapy may also be necessary in the presence of learning, social, and psychological issues that may manifest with this condition.

Normally, humans receive 23 chromosomes from each parent during the conception process, for a total of 46. In some cases, a chromosomal mosaicism can occur, resulting in excessive or inadequate sex chromosomes. Such is the case with XXY syndrome, which occurs when a male child is born with an additional X chromosome, bringing his individual total to 47. There is no known link between this condition and contributory factors, such as the age of the mother or a familial history of this type of chromosomal mosaicism. Essentially, XXY syndrome is understood to be a genetic condition that presents randomly.


Generally, symptoms associated with XXY do not manifest in a pronounced way until one's late adolescent years into adulthood. Most men will seek a medical consultation when faced with issues of infertility, a common complication of XXY syndrome. Following a consultation and physical examination, a battery of diagnostic tests may be performed, including a semen count and various serum analyses. The administration of serum analyses are generally performed on a blood sample and are utilized to evaluate hormone levels, including testosterone, estrogen, and luteinizing hormone (LH).

Individuals with XXY syndrome may experience a variety of signs and symptoms prior to discovering they may be infertile. Most adolescent males may exhibit abnormal physical proportions affecting their trunk and limbs, such as an abnormally short trunk and long limbs. Many with XXY syndrome are often considered of above average height when compared to their peers. An individual may also have excessively small genitalia and present with breasts, a condition known as gynecomastia. Additionally, he may lack hair in traditional areas, such as the face and pubic region.

There are many complications that may accompany a presentation of XXY syndrome in addition to its physical characteristics. Individuals with this condition often experience learning issues at a young age, including language difficulties presenting as impaired speech or comprehension, and may develop attention deficit hyperactivity disorder (ADHD) or dyslexia. Additional signs may include an increased susceptibility to lung disorders, certain cancers, and psychological issues, including pronounced depressive episodes.

Testosterone is frequently given to counteract and correct certain presentations of the disorder and ease symptoms. The administration of testosterone generally aids with alleviating the psychological issues that arise with this condition, enabling the individual to grow body hair, and may help to improve the patient's overall physical appearance. Surgery may also be performed to minimize or remove any gynecomastic presentation and restore a semblance of normalcy to the chest area. Counseling, including educational and social support, is often considered a valuable tool to help the individual better understand and cope with his condition. It should be noted that the infertility associated with this condition is usually permanent.


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Post 11

Oh, I just noticed something, XXY is not that rare affecting between 1:500 to 1:1000 live male births.

And another little known statistic is that XXY appears in 50 percent of all spontaneous abortions.

Of those of us that exist I suppose one could say we're pretty lucky to be here?

Post 10

But not to leave this subject on such a depressing note. On Friday night I'll be attending the second performance of "Hansel & Gretel" a melodrama, where my daughter plays Gretel.

I also have a son and an ex wife and alimony! So all is not lost for even the worst case scenarios. Somehow, through it all, we succeeded and did what many other married couples end up doing: had a family.

Post 9

So what do you suppose happens when a 16 year old boy discovers he infertile and that his testicles are tiny? Odd, that. I never compared what I was learning in school to myself. A paradox. XXY's can be quite intelligent but lack something that connects the dots and makes everything sense.

The boy who knows he's never got on well with other people, who knows he has a history of academic failure and no inclination to leave his parents' home, yet hates being at his parents' home.

I know what he does. I am him. He tries to kill himself.

Post 8

I'd say testosterone is used to grow XXY boys up, as it grows XY boys up. I'd say counseling was a really good idea but it rarely ever happens. And I'd say another little known surgery not mentioned here will have a major psychological benefit to many XXY boys approaching adulthood, which is adult size prosthetic testes. One can't really lead a near to normal life when one's testicles are as big as a pea!

XXY is considered to be a disorder of sex differentiation, so anything to enhance masculinity, like testosterone therapy for life and mastectomy where required might be thought of as mandatory?

Everybody who thinks about it knows that testosterone causes the penis to grow bigger, but

most people don't know it's the production of testosterone in the testes that make them bigger. But we don't get bigger testicles at puberty. We get testicular atrophy (shrinkage) instead.

Imagine you're 16ish and your parents are discussing the size of your testicles with your doctors and your other family members, then you find out about it, accidentally? Kind of lets the little wind there was out of your sails.

Post 7

Another thing: my doctors did was tell my parents everything. They knew everything before I knew everything. Stuff about my supposedly small genitals, small testes for sure that was true, but that's all that was true! Then my parents took it upon themselves to tell other adult family members like my uncles and aunties and grandparents!

My parents were offered genetic counseling, but not me. I wasn't offered anything in that line. There was no information offered about the connection between educational issues and being XXY.

Endocrinologists aren't interested in and don't study the educational and social aspects of endocrine disease.

It's good to see that as time has passed, better and more appropriate services are offered to XXY's themselves, they being the ones who really do have to live with being XXY.

Post 6

When I first saw my Endocrinologist, when I was 16ish and still legally a minor, he told be straight out that I was probably infertile. He explained to me that the doctors merely assumed all XXY's were and that there was no need to do fertility testing. That was back in 1976.

Not being one who likes to take "no" for an answer, I determined to do my own fertility testing. I knew exactly what to look for as human biology was my best subject in school and we'd examined frog sperm in our lessons.

Alas, my doctor was right. There was no need to do fertility testing with me.

Post 5

Well actually I'm not a mosaic simply by being XXY, the word used to describe my chromosomal constitution, my karyotype, is "aneuploid" which refers to a chromosomal count greater or lessor than the normal 46. So a Turner woman 45X is a aneuploid, as is a 47XYY man and an 47XXX woman.

Mosaics are people with a mixture of chromosomal types, such as some cells may be 46XY and others may be 47XXY, which is often expressed as XY/XXY mosaic. Some of my best friends are XY/XXY mosaics. One of my friends is even XXY/XXXY mosaic.

Post 4

The weird thing here is that I advertise WiseGeek online, and I have more than one channel to facilitate the free flow of information.

I'm doing my absolute level best to get other XXY guys especially to comment on your site. But as the literature shows, XXY guys are generally passive and shy, not wanting to draw attention to themselves, or making a stand on any matter or publicly protesting.

I, on the other hand, are more than happy to express my opinion even when I know that opinion will be altered or deleted.

That's what having the right level of testosterone does, makes me much more like a regular man. (cheesy grin)

Post 2

Now would be a good time to point out that recent research indicates that not all XXY's are infertile and even those with little or no sperm in their ejaculate may still have viable sperm cells in their testes that can be extracted using the I.C.S.I. process, (Intracytoplasmic Sperm Injection) and IVF treatment in order to father their own children.

Darius A Paduch, Ronnie G Fine, Alexander Bolyakov, Joseph Kiper (Affiliation: Department of Urology and Reproductive Medicine, Weill Medical College of Cornell University, New York, NY 10065, USA. dap2013 at

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