Diagnosis of Klinefelter Syndrome

How do health care providers diagnose Klinefelter syndrome (KS)?

The only way to confirm the presence of an extra chromosome is by a karyotype (pronounced care-EE-oh-type) test. A health care provider will take a small blood or skin sample and send it to a laboratory, where a technician inspects the cells under a microscope to find the extra chromosome. A karyotype test shows the same results at any time in a person's life.

Tests for chromosome disorders, including KS, may be done before birth. To obtain tissue or liquid for this test, a pregnant woman undergoes chorionic villus (pronounced KAWR-ee-on-ik vil-uhs) sampling or amniocentesis (am-nee-oh-sen-TEE-sis).1 These types of prenatal testing carry a small risk for miscarriage and are not routinely conducted unless the woman has a family history of chromosomal disorders, has other medical problems, or is above 35 years of age.

Factors that Influence when KS is Diagnosed

Because symptoms can be mild, some males with KS are never diagnosed.2

Several factors affect whether and when a diagnosis occurs:

  • Few newborns and boys are tested for or diagnosed with KS.
  • Although newborns in the United States are screened for some conditions, they are not screened for XXY or other sex-chromosome differences.
  • In childhood, symptoms can be subtle and overlooked easily. Only about 1 in 10 males with KS is diagnosed before puberty.1
  • Sometimes, visiting a health care provider will not produce a diagnosis. Some symptoms, such as delayed early speech, might be treated successfully without further testing for KS.
  • Most XXY diagnoses occur at puberty or in adulthood. ?Puberty brings a surge in diagnoses as some males (or their parents) become concerned about slow testes growth or breast development and consult a health care provider.
  • Many men are diagnosed for the first time in fertility clinics.3 Among men seeking help for infertility, about 15% have KS;4

Source: NICHD (NIH)1

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Back to: « Klinefelter Syndrome

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How is Klinefelter syndrome diagnosed?

A chromosomal analysis (karyotype) is used to confirm the diagnosis. In this procedure, a small blood sample is drawn. White blood cells are then separated from the sample, mixed with tissue culture medium, incubated, and checked for chromosomal abnormalities, such as an extra X chromosome.

The chromosome analysis looks at a number of cells, usually at least 20, which allows for the diagnosis of genetic conditions in both the full and mosaic state. In some cases, low-level mosaicism may be missed. However, if mosaicism is suspected (based on hormone levels, sperm counts, or physical characteristics), additional cells can be analyzed from within the same blood draw.

Source: NHGRI (NIH)2

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A diagnosis of Klinefelter syndrome is often suspected based on the presence of characteristic signs and symptoms. Additional testing can then be ordered to confirm the diagnosis. This generally includes a chromosomal analysis (called a karyotype).[5, 3]

It is also possible to diagnosis Klinefelter syndrome before birth through chorionic villous sampling or amniocentesis.[5] Last updated: 10/12/2015

Source: GARD (NIH)3

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Testing for Klinefelter syndrome

See your GP if you have concerns about your son's development or you notice any troubling symptoms of Klinefelter syndrome in yourself or your son.

Klinefelter syndrome isn't necessarily anything serious, but treatment can help reduce some of the symptoms if necessary.

In many cases, it's only detected if a man with the condition undergoes fertility tests.

Your GP may suspect Klinefelter syndrome after a physical examination and they may suggest sending off a sample of blood to check reproductive hormone levels.

The diagnosis can be confirmed by checking a sample of blood for the presence of the extra X chromosome.

Source: NHS Choices UK4

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  1. Source: NICHD (NIH): nichd.nih.gov/ health/ topics/ klinefelter/ conditioninfo/ Pages/ diagnosed.aspx
  2. Source: NHGRI (NIH): genome.gov/ 19519068/ learning-about-klinefelter-syndrome/ 
  3. Source: GARD (NIH): rarediseases.info.nih.gov/ diseases/ 8705/ klinefelter-syndrome
  4. Source: NHS Choices UK: nhs.uk/ conditions/ klinefelters-syndrome/ 

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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.