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Klinefelter's syndrome What we need to know

Klinefelter syndrome is a chromosomal disorder characterized by the presence of an extra X chromosome in males. This is caused by meiosis, a random process where the father's XY or mother's XX chromosome pairs do not separate, and thus the embryo receives two X chromosomes in addition to the Y chromosome.

Normally, a female baby has 2 X chromosomes (XX) and a male baby has 1 X and 1 Y (XY), but in Klinefelter syndrome, a boy is born with an extra copy of the X chromosome (XXY).

Boys and men with Klinefelter syndrome are genetically male and are often unaware that they have an extra X chromosome, which can cause confusion and, in many cases, serious psychological problems.

Klinefelter syndrome symptoms

Klinefelter syndrome usually does not cause any obvious symptoms in early childhood. In adults, the signs and symptoms of the syndrome vary significantly. Most boys have few or only mild symptoms. For some, this condition has a noticeable effect on growth and appearance.

Signs and symptoms of Klinefelter syndrome also vary by age.

Symptoms of Klinefelter in children:

  • weak muscles;
  • take longer than usual to learn to sit and walk;
  • speech delay;
  • testicular defects;
  • height above average;
  • Longer legs, shorter torso, and wider hips than other adolescent boys;
  • delayed or incomplete puberty;
  • After puberty, less facial and body hair;
  • congenital underdevelopment of the gonads;
  • enlarged breasts (gynecomastia);
  • weak bones;
  • are characterized by shyness;
  • have difficulty expressing thoughts and feelings and socializing;
  • They learn spelling and mathematics with difficulty.

In adult men:

  • absence of sperm;
  • congenital underdevelopment of the gonads;
  • less sexual desire;
  • height above average;
  • weak and brittle bones (osteoporosis);
  • less facial and body hair;
  • enlarged breasts;
  • increased belly fat;
  • Less muscle mass.

Risk factors

Klinefelter syndrome occurs by chance, it is not a genetic disease. It is possible to have a child with this syndrome at an earlier age, however, as a woman ages, the risk of having a child with Klinefelter syndrome also increases.


There are two main types of tests available to prevent fetal syndromes during pregnancy (prenatal period): screening tests and diagnostic tests. Screening and diagnostic tests determine whether a fetus has a low or high chance of developing various syndromes.

If screening tests show that you have a high risk of having a baby with Klinefelter syndrome, it is recommended that you also have a diagnostic test to determine whether the fetus has the genetic disorder.

1. Screening Tests – A prenatal screening test can determine if your baby is more or less likely to have birth defects, many of which are genetic disorders. These tests include blood tests, specific ultrasounds, and prenatal cell-free DNA screening.

2. Diagnostic tests – after the screening test, the final answer is given by the diagnostic test, which checks the genetic material of the fetus and therefore can also find out whether the fetus has a genetic disorder. Invasive and non-invasive prenatal diagnostic tests ((NIPT) Verasity, Veragen) are the only, safe and effective way to confirm the diagnostics.

Be aware that some diagnostic tests, such as chorionic villus sampling and amniocentesis, carry a small risk of miscarriage.

Learn more about prenatal diagnostics → (


  • anxiety and depression;
  • social, emotional and behavioral problems such as low self-esteem, emotional immaturity and impulsivity;
  • Infertility and sexual function problems;
  • Cardiovascular diseases;
  • Oncological diseases;
  • type 2 diabetes, high blood pressure (hypertension) and high cholesterol;
  • autoimmune disorders (when the immune system mistakenly attacks the body), such as lupus and rheumatoid arthritis;
  • oral problems;
  • A number of complications caused by Klinefelter's syndrome are related to low testosterone levels (hypogonadism - a disease in which there is a failure of the function of the gonads and a violation of the synthesis of hormones in the body)


There is no complete cure for Klinefelter syndrome, but there are solutions to alleviate the problems caused by it and prevent some diseases. Speech and language therapy is effective for boys with Klinefelter syndrome.

For some men, lifelong supplementation with testosterone is effective. The hormone improves bone density, reduces the frequency of fractures and stimulates the development of a masculine appearance. Physiotherapy and psychological support are effective.



For prenatal screening of Klinefelter's syndrome, "Synevo" laboratory offers the following studies:

Name of the test Category Price CODE Response time (working day) ** Location of the analysis **** Buyhf: categories

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