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Jacobs syndrome What we need to know

Most people have 46 chromosomes in each cell. In males, this usually involves one X chromosome and one Y chromosome (XY). XYY syndrome is a genetic disorder in which a male has an extra copy of the Y chromosome in each cell (XYY).

Sometimes this mutation is only in some cells. Males with XYY syndrome have 47 chromosomes due to an extra Y chromosome. According to the National Institutes of Health, XYY syndrome occurs in one out of every 1000 boys.

Synonyms of XYY syndrome

  • 47, XYY syndrome;
  • Jacobs syndrome;
  • XYY karyotype;
  • YY syndrome.

For the most part, people with XYY syndrome live typical lives. Men with the syndrome usually do not have any distinguishing physical features and have normal sexual development.


XYY syndrome is the result of a random mutation in the male genetic code. Most cases of XYY syndrome are not inherited. Researchers do not believe it has any genetic predisposition. A random error (chromosomal mutation) can occur during the formation of sperm or during various processes of embryo formation.


The signs and symptoms of Jacobs (XYY) syndrome are different for every person and will also manifest differently in different age groups.

Symptoms in a newborn who has XYY syndrome may include:

  • hypotonia (weak muscle tone);
  • motor impairment, such as walking or crawling;
  • Delayed or difficult speech.

In a young child or teenager with XYY syndrome, symptoms may include:

  • diagnostics of autism;
  • attention difficulties;
  • Impairment of motor skills such as writing;
  • delayed or difficult speech;
  • emotional or behavioral problems;
  • hand tremors or involuntary muscle movements;
  • hypotonia (weak muscle tone);
  • learning disability;
  • high altitude
  • Adult infertility is a possible symptom of XYY syndrome.


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 Jacobs syndrome, it is recommended that you also have a diagnostic test to determine if 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 → (

Complications and solution

XYY syndrome cannot be cured. But treatment can help relieve symptoms, especially if it's diagnosed early.

People with XYY syndrome often manage symptoms such as speech and cognitive problems with the help of medical specialists. With increasing age, it is advisable to visit a reproductive specialist to solve infertility problems.

Effective for alleviating the symptoms of Jacobs (XYY) syndrome:

  • speech therapy courses;
  • physiotherapy or occupational therapy;
  • Educational therapy.



"Synevo" laboratory offers the following tests for prenatal screening of Jacobs syndrome:


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

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