XYY Syndrome

By | June 10, 2022

XYY syndrome is a numerical chromosomal aberration that can produce a male phenotype with an abnormal karyotype of up to (52, XXXXXXYY). Externally, the affected person cannot see the genotypic anomaly. Treatment is only needed if people actually develop symptoms, such as a heart defect.

What is XYY Syndrome?

Numerical chromosome aberrations are non-hereditary changes in the number of chromosomes. In this phenomenon, chromosomes either occur more than once or are completely absent. The XYY syndrome is counted among the numerical chromosomal aberrations. For meaning of cd in English, please visit sportingology.com.

The condition is also known as XYY trisomy, Diplo Mann syndrome or supermasculinity syndrome, Jacobs syndrome, and Diplo Y syndrome. Sometimes the term polysomy Y is used synonymously. Chromosomal aberration is an aneuploidy of the sex chromosomes.

Phenotypically, individuals with the syndrome are clearly male. Their karyotype is also male, but contains a double Y chromosome. In individual cases there may also be several X chromosomes. Karyotypes such as (52, XXXXXXYY) are conceivable combinations for people with XYY syndrome.

The first case of the anomaly was documented in 1961. The working group Avery A. Sandberg is considered the author of the first description. Since the affected person was completely inconspicuous in terms of phenotype, the find was an accidental find. The prevalence of the anomaly ranges from 1 in 590 cases in Northern Europe to 1 in 2000 cases in the US.


Numerical chromosomal aberrations arise due to maldistribution of homologous chromosomes during meiosis. During the formation of male germ cells, the Y chromosome normally undergoes a non-disjunction event in meiosis II, which does not allow the two chromatids to diverge from each other.

Normally, this results in a ratio of 50 percent sperm with the usual karyotype (23, X), 25 percent sperm correspond to the karyotype (24, YY) and another 25 percent have no gonosomes. If one of the (24, YY) sperm fuses with an egg cell of karyotype (23, X), the resulting zygote will carry karyotype (47, XYY). Following this fusion, there is a nondisjunction of homologous chromosomes within the egg cell and within the sperm during meiosis I.

Nondisjunction of the sister chromatids occurs in meiosis II. Thus, the maximum numerical chromosomal aberration as a karyotype is (52, XXXXXXYY). Importantly, XYY syndrome has no underlying hereditary basis. Instead, the anomaly is caused by maldistribution in egg cells and sperm of the karyotypes described.

Symptoms, Ailments & Signs

The symptoms of XYY syndrome are varied. Not everyone affected has to have the same symptoms. Many of the patients have an increased height on average and are characterized by accelerated growth in childhood.

Since the patients’ body weight does not increase to the same extent, the patients often appear extremely slim. Severe acne in adolescence is reported in many cases. A high testosterone level can also be characteristic. Men with XYY syndrome also often have enlarged facial proportions, such as large ears or a conspicuously strong bridge of the nose.

Their hands and feet are often longer than average. Some of those affected have a breastbone dent. Also, there may be a bony connection between the ulna and the radius called radio-ulnar synostosis. In individual cases, the patients suffer from heart defects of various kinds. Undescended testicles can also occur as part of the syndrome.

Development during adolescence is somewhat delayed due to the extra Y chromosome. This connection does not suggest a mental delay in development, but rather relates to the fine motor skills of those affected. Specific male behavioral patterns can be more evident in the behavior of those affected due to the increased testosterone level. Short-tempered temperament, attention deficit and increased restlessness are common.

Diagnosis & course of disease

In many cases, the diagnosis of XYY syndrome corresponds to an incidental finding. Since there are usually no phenotypic abnormalities and the anomaly is usually limited to the genotype, many of those affected do not find out about their anomaly until the end of their days. Ultimately, there can be no question of an actual disease value in the case of XYY syndrome.

For this reason, the diagnosis is usually no longer relevant. The prognosis for people with the syndrome is extremely favorable, since there are no restrictions on life expectancy and fertility is not further impaired in most cases.


The XYY syndrome represents a numerical chromosomal anomaly, which, however, has little medical significance. According to current knowledge, in contrast to other chromosomal anomalies, there are almost no significant complications. Those affected usually do not even know anything about their anomaly.

It is often an incidental finding. Some of those affected may have characteristics that indicate an increased concentration of the male sex hormone testosterone. However, they are usually within the normal range. Contrary to earlier assumptions, the affected men have normal intelligence and are fully capable of procreation.

However, the outward appearance and demeanor may differ somewhat in relation to other “average” men. XYY men are said to be a bit more short-tempered than normal men, which can eventually lead to more aggressive behavior. But there are no clear findings on this either. Furthermore, in contrast to girls, development in adolescence is somewhat more delayed than in other boys.

Fine motor skills should also be poorly developed. Due to the increased testosterone concentrations, the XYY men are larger on average and suffer from undescended testicles more often. If left untreated, this can limit fertility in individual cases. Sometimes different heart defects also occur, which may later acquire medical significance. Overall, however, the prognosis is very good. Life expectancy is normal.

When should you go to the doctor?

Naturally, the syndrome can only occur in males. Therefore, parents should consult a doctor with their offspring as soon as they notice any irregularities in the growth and development process of their child. Optical abnormalities are usually shown by the very large body size of the boy. At the same time, the weight of the affected person is very low in direct relation to their height. Despite a good intake of food or a generally high-calorie diet, there is no significant increase in body weight.

If a severe change in the skin’s appearance is noticed in adolescence, it is advisable to consult a doctor. In the case of severe acne, numerous pimples or emotional distress due to the visual appearance, a doctor’s visit is necessary. If the proportions in the facial area are unusual, this indicates a health problem. Although no physical discomfort or pain occurs, a doctor’s visit should be made to clarify the cause.

A doctor is also required in the event of irregular heart rhythms, undescended testicles and behavioral problems. Disorders and deficits in attention, a very quick-tempered demeanor and an exceptionally high temper are signs of a hormonal imbalance. In the event of severe restlessness, fine motor skills disorders or intellectual development delays, we recommend consulting a doctor. Conflict situations occur remarkably often in which the person concerned shows no signs of de-escalation.

Treatment & Therapy

Ultimately, XYY syndrome is not necessarily a disease. In fact, almost all of those affected remain asymptomatic until the end of their lives and sometimes do not even know anything about their anomaly. In these cases there is no need for therapy.

In some exceptional cases there is infertility or at least a worsened sperm quality. This can become a problem when trying to have children. A spermiogram can provide information about the sperm quality. If you want to have children despite reduced sperm quality, artificial insemination can take place.

Symptoms of the XYY syndrome that actually require therapy are ultimately only the heart defects, which, however, are by no means present in all cases. Depending on the type of heart defect, surgery and drug therapy may be required. Undescended testicles should also be treated under certain conditions, for example with hormone therapy. There is no causal treatment for patients with XYY syndrome.


Preventive measures to prevent XYY syndrome hardly exist. External factors do not seem to play a role in the syndrome. The karyotype of the egg cell and the sperm at meiosis alone determine the presence of the anomaly for the resulting zygote.


There is no cure for XYY syndrome. However, since the affected men do not have any symptoms due to the chromosomal abnormality, no follow-up care measures are usually necessary. In some cases, the fertility of those affected by the XYY syndrome is minimally reduced. However, this is usually not clinically relevant.

Very rarely, boys with XYY syndrome have delayed development compared to children of the same age. There are sometimes deficits, especially in the area of ​​fine motor skills. In these cases, long-term care by an occupational therapist is possible. In principle, however, such restrictions resolve themselves after a few years, so that such measures are not absolutely necessary.

In addition, the affected boys can develop special behavioral patterns due to the additional Y chromosome and the associated increased testosterone level. These can manifest themselves from the beginning of puberty through attention disorders, nervousness or aggressiveness. For this reason, psychotherapeutic care may be necessary for a short or possibly long period. Nevertheless, intensive follow-up care is not necessary in these cases either. The lifespan of the affected men is not limited by the XYY syndrome. Nevertheless, a healthy lifestyle is recommended.

You can do that yourself

Self-help measures are not sufficient to influence a change in the chromosomes. In many cases, there are no further health impairments in the course of life. Therefore, there is often no need for action with them.

If there are any abnormalities in behavior, targeted training and exercise sessions should be carried out with the person concerned. It is advisable to seek professional therapy. In addition, changes in behavior can be brought about independently. It is usually important to have the support of the social environment and immediate family members.

In everyday life, jointly developed rules can be set up to help the person concerned to build up a stable social bond outside of the family circle. Contact with other people can be practiced by re-enacting everyday situations. As a result, the person concerned becomes aware of certain behavioral patterns and can then jointly optimize them.

Exercises can also be carried out that lead to a reduction in restlessness or hecticness. Methods such as yoga, relaxation exercises, autogenic training or mental techniques help to find inner peace and consciously bring about this state if necessary. Food intake should also be monitored, especially in people who are very fidgety. Consuming caffeine or products containing sugar often makes their situation worse and should be avoided.

XYY Syndrome