Jacobs syndrome (XYY) | What we need to know

Human karyotype (set of chromosomes) consists of 23 pairs, or 46 chromosomes. 22 pairs of chromosomes are autosomal, and the twenty-third pair are sex chromosomes, which determine sex. In the male gender, the sex chromosomes are represented by the XY chromosome, and in the female by the -XX chromosome.

XYY or Jacobs syndrome is a genetic pathology in which the male fetus has sex chromosomes with X and YY chromosomes, that is, the cells contain not 46, but 47 chromosomes (at the expense of an extra Y chromosome). The incidence of this condition is 1:1000 live births.

In most cases, boys with XYY aneuploidy are no different from other children; Sometimes they are distinguished by a higher height compared to the age norm, more or less pronounced muscle weakness, learning or speech difficulties, and others. Their sexual development is mostly within the norm, but there are also cases of infertility.

Most cases of XYY syndrome are not inherited from a parent, but are the result of a "mistake" or mutation that occurs during cell division. Such a mutation may develop both during sperm formation and at the early stage of embryo (germ) cell division. In the latter case, mosaicism sometimes occurs, that is, some cells contain a normal set of chromosomes – XY chromosomes, and some have XYY chromosomes.


The characteristic symptoms of XYY syndrome are different at different ages:

In infants, there are:

  • Muscle hypotonia
  • Delay in the development of motor skills (groping, walking)
  • Delay in speech development

In adult children:

  • Autism spectrum disorders
  • Attention and concentration difficulties
  • Delay in the development of motor skills (writing, fine motor skills)
  • Delay in speech development
  • Emotional and behavioral problems
  • Tremors, involuntary movements
  • hypotonia (muscle weakness)
  • learning problems
  • Taller than average

Fertility disorders are often seen in adults.


Diagnosis of XYY syndrome is sometimes delayed until adulthood, when fertility issues arise and research begins. Research is done through genetic analysis.

The best option for diagnostics is prenatal non-invasive diagnostics, which examines both monogenic and chromosomal disorders.


XYY syndrome cannot be cured. Symptomatic treatment is needed at an early age, which provides the opportunity to minimize the existing disorders:

  • speech therapy
  • Physical/occupational therapy – for timely development of motor skills
  • Educational work - selection of a specific teaching method

XYY syndrome in most cases does not disturb the normal rhythm of life of these people.



For prenatal screening of Jacob's syndrome (XYY), "Synevo" laboratory offers the following tests:

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






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