Jacobs Syndrome

What is Jacobs Syndrome?

Jacobs syndrome is rare male gender oriented chromosomal disorder. In human, normally 46 chromosomes are arranged and the sex determining chromosomes X and Y specifically arranged for determining male and female. In female both sex-determining chromosomes are XX and in male, detection of sex chromosomal arrangement is XY. But in Jacobs syndrome one extra Y is added, means the chromosomal arrangement shows XYY. Therefore, the affected male has 47 chromosomes due to the presence of one extra Y chromosome1,2.

Jacobs Syndrome face

National Institutes of Health surveyed the incidence rate of Jacobs Syndrome, and estimate that 1:1000 means 1 boy is get affected within 1000 boys3.


During the formation of a male genetic code random mutation occur and outcome of this haphazard chromosomal mix-up XYY arrangement develops. The affected individual inherits two YY chromosome from his father, instead of one. The haphazard chromosomal coding is not same for every cell. It depends upon when an error takes place. In some cases, a genetic error occurs during the sperm formation, whereas or at a different stage of embryo development. In the second case, some cells may not have a defective chromosomal arrangement. Therefore, in this case, some cells are XY genotype and others XYY genotype.

The cause of Jacob syndrome may or may not be inherited, which means the hereditary transmission of this abnormal genetic mutation should not always transfer to the next generation of the affected individual. Children of an affected individual can have a normal genetic code3,4.

Jacobs Syndrome gene defect chromosome


The Jacob syndrome affected individuals have different symptoms at different stages of life.

Jacobs Syndrome Symptoms for Baby Boy

  • Weak muscle tone (hypotonia)
  • Delayed crawling or walking due to impediment of motor skill development
  • Speech difficulty or delaying of speech

Jacobs Syndrome Symptoms for teenagers or a young child

  • Abnormalities related to mental health, which include autism, attention difficulties, learning disabilities, immature behavior and emotional or behavioral issues
  • Motor skill impediment causes delayed writing ability
  • Speech difficulty
  • Less gripping power or less muscle strength causes less gripping power due to weak muscle tone (hypotonia)
  • Involuntary muscle movement causes trembling of hand
  • The average height is more than normal individual
  • Prone to cystic acne at adolescent age due to hormonal disbalance

Apart from above mentioned symptoms following are some complex symptoms associated with Jacobs Syndrome:

  • Arthritis a common joint disorder
  • Straightening of finger become difficult after bending of finger due to flexon deformity (Camptodactyly)
  • Joint inflammation
  • Stiffness of joint
  • Impairment of joint mobility
  • Swelling of pericardium
  • Chest pain

Adult males have similar sexual potency and libido, but some affected individuals have fertility related issues. Though some document reported no fertility issue arise with Jacobs Syndrome1,3.


Usually, no other complications are associated with Jacobs syndrome apart from mentioned symptoms. But sometimes Klinefelter syndrome may present along with Jacobs syndrome. In Klinefelter syndrome, a number of a chromosome may be 48, 49 or 50. All extra chromosomes are X type2.


Usually, Jacobs syndrome may not be able to diagnose at the childhood. However, prenatal (before birth) diagnosis can be possible by conducting chorionic villus sampling or amniocentesis test. A little portion of placenta collected for chorionic villus sampling and little amount of fluid in which fetus is immersed collected for amniocentesis test.

At the adulthood, infertility issues like low sperm count may need to identify the possible cause and that time incidentally Jacobs syndrome identified. For symptomatic analysis, reading assessment, speech assessment, or language assessment is conducted. The probability of the presence of dyslexia in school going children is ruled out.

If symptomatic analysis and pre-medical history of the patient need to conduct the chromosomal analysis. Genetic disorder including Jacobs syndrome can be diagnosed by chromosomal analysis3,4.


Jacobs syndrome is non-curable disease, but treatment can assist in symptomatic reduction, particularly in the case of early diagnosis. The treatment plan is symptoms dependent, like reduction of speech problem, learning difficulties. In the case of adults, reproductive issues like infertility are one of the primary concern of treatment. The following treatment options are usually applicable for Jacobs syndrome depending upon the patient’s need.

Speech therapy

Jacobs affected patients may have speech difficulty and motor skill disabilities. Different healthcare facilities are available for treating patients. These implementations are can improve the condition.

Physical or occupational therapy 

Early interventions of physical and occupational therapy can improve motor skills, especially for younger age children. The probability of muscle strength improvement also higher by applying these therapies.

Educational therapy

Learning disability can be improved by providing special education therapy, in which educational coordinators assists them to improve their concentration. Behavioral issues can also minimize by educational therapy3,4.


Individuals affected with Jacob’s syndrome usually has normal life span with the different mentioned symptoms. Sometimes Jacobs syndrome remains undetected throughout the life span, however, detection can improve the patient condition3.


Jacobs Syndrome images 4

Jacobs Syndrome symptoms

Jacobs Syndrome pictures


  1. Jacobs syndrome; Right Diagnosis; Online available at http://www.rightdiagnosis.com/j/jacobs_syndrome/intro.htm
  2. Raquel Hunter; Jacob Syndrome; MAMASHEALTH.COM; Online available at http://www.mamashealth.com/syndrome/jacob.asp
  3. Kimberly Holland; XYY Syndrome; healthline; Online available at http://www.healthline.com/health/xyy-syndrome#Overview1
  4. XYY Syndrome;National Organization For Rare Disorder; Online available at https://rarediseases.org/rare-diseases/xyy-syndrome/

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