A diagnosis of Klinefelter syndrome can be made based on a number of physical characteristics and symptoms, and confirmed with diagnostic chromosomal analysis.
Unlike several other congenital conditions, there is currently no screening of newborn babies with Klinefelter syndrome in the United States. The symptoms are often overlooked in childhood and it is estimated that only 10% of boys with the syndrome are diagnosed before reaching puberty.
Occasionally parents may notice abnormal signs in an infant or young child, such as undescended testicles, weak muscles and delayed motor skill or speech development, which prompts them to seek medical advice and a potential diagnosis. However, the symptoms of Klinefelter syndrome are often very mild. Thus, some affected males may never be diagnosed with the condition. In fact, many males are only diagnosed as adults when they are unable to conceive a child due to infertility issues.
The only physical sign of Klinefelter syndrome that may be noticeable in infants or young boys is undescended testicles. As boys reach the age of puberty, other physical signs may become more obvious. These may include tall stature with long legs, short torso and broader hips and enlarge breast tissue (gynecomastia).
A genital examination is also usually carried out to assess the size of the penis and testicles, as well as the quantity of pubic hair. Males with Klinefelter syndrome tend to have a small penis and testicles and less pubic hair than other males that are not affected.
The only way to confirm the presence of an additional X chromosome and the diagnosis of Klinefelter syndrome is to conduct a karyotype test to analyze the sex chromosomes. For this test, a small blood or skin sample is taken and sent to a laboratory for investigation. This can be done at any point throughout an individual’s life and, if performed correctly, will yield the same result because the chromosomes remain constant.
There are also some chromosomal tests that can be conducted on the fetus before the birth of the baby. For this test, a tissue or liquid sample is taken from a pregnant woman during chorionic villus sampling or amniocentesis. However, these tests are not routinely conducted, unless there is an increased risk of an inherited chromosomal disorder, because they are associated with a higher likelihood of miscarriage.
Blood tests may also be required during the diagnostic process to determine the hormone levels in the blood. Most males with Klinefelter syndrome will have a lower concentration of testosterone than other males, which is linked to the extent of the symptoms associated with the condition. The results of this test are helpful to understand the impacts of the condition and help in deciding what treatment actions to take.
Examination of the semen can be useful, particularly for men who are struggling with infertility and having difficulty conceiving a child. This involves a sample of the semen, which is analyzed for sperm count and aids in the treatment decisions of the condition.