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XXYY syndrome What we need to know

XXYY syndrome is a sex chromosome abnormality in which males have an extra X and Y chromosome. XXYY is a genetic disorder that occurs only in males and is characterized by the presence of extra sex chromosomes compared to the typical male 46,XY karyotype. 48, XXYY syndrome has previously been described as a variant of Klinefelter syndrome because men with the syndrome have similar physical features, but the medical and neurological features are more complex than those typical of 47, XXY/Klinefelter syndrome.

Human cells normally contain two sex chromosomes, one from the mother and one from the father. Normally, females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). Therefore, people with XXYY are genotypically male. Men with XXYY syndrome have 48 chromosomes instead of 46. This is why XXYY syndrome is sometimes written as 48,XXYY syndrome or 48,XXYY.

The extra X chromosome prevents the production of sperm, and usually the sperm of 48,XXYY men does not contain sperm. Testosterone treatment has no effect on this. However, although men are infertile, they lead sexually active lives.

48, XXYY syndrome synonyms

  • XXYY syndrome;
  • 48, Klinefelter syndrome XXYY variant;
  • 48,XXYY Klinefelter's syndrome.

Signs and symptoms

48, XXYY syndrome symptoms are:

  • Impairment of motor skills such as writing;
  • delayed or difficult speech;
  • hypotonia;
  • twisted neck (torticollis);
  • Wrinkle of the skin of the upper eyelid;
  • large distance between the eyes (hypertelorism);
  • congenital heart diseases;
  • Kidney malformations and skeletal disorders;
  • flat feet
  • scoliosis.

other states

  • epilepsy (~15%);
  • Tremor (~60% in adults);
  • asthma/allergy (~60%);
  • severe dental problems (~90%);
  • Gastrointestinal disorders (~ 90%);
  • Constipation, eosinophilic esophagitis;
  • weakness of the joints;
  • sleep apnea;
  • thrombosis (~18%) and type 2 diabetes (~20% in adulthood);
  • high altitude
  • small testicles (microorchism);
  • Decreased growth of facial and body hair;
  • Fatigue;
  • Depression;
  • inguinal hernia;
  • Enlargement of breast tissue (gynecomastia).


Syndrome 48,XXYY is not hereditary; It is usually formed accidentally during the fusion of reproductive cells (egg and sperm). In 48,XXYY syndrome, the extra sex chromosome almost always comes from a sperm cell. If such a sperm fertilizes a normal egg with one X chromosome, the resulting child will have two X chromosomes and two Y chromosomes in each cell of the body. There is no evidence that XXYY syndrome is caused by any parental behavior before or during pregnancy. It is not associated with environmental, drug or alcohol exposure, disease or medication.


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 XXYY 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 → (


48, In XXYY syndrome, comprehensive interdisciplinary care is important for assessment and management of developmental, medical, and psychological conditions. A thorough physical examination, renal ultrasound examination and echocardiography are required to establish the diagnostics. Vision/hearing tests and dental check-ups are important throughout life.



For prenatal screening of XXYY 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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