What is XYY syndrome? How is it diagnosed? What are the symptoms and physical characteristics associated with the condition? Find answers to these questions and more in this in-depth article.

Understanding XYY Syndrome: An Overview

XYY syndrome, also known as Jacob’s syndrome or Superman syndrome, is a rare chromosomal condition in which a male individual is born with an extra Y chromosome. This genetic alteration, which occurs in approximately 1 out of every 1,000 male births, is the result of a random event during the division of the sperm cell prior to conception.

Causes of XYY Syndrome: Unraveling the Genetic Puzzle

The usual number of chromosomes in a human cell is 46, organized into 23 pairs. The 23rd pair consists of the sex chromosomes, with females typically having two X chromosomes and males having one X and one Y chromosome. In the case of XYY syndrome, a male individual is born with an extra Y chromosome, resulting in a karyotype of 47,XYY.

This extra Y chromosome is not a hereditary trait, meaning that fathers with XYY syndrome do not pass the condition on to their sons. The genetic alteration occurs due to a process called nondisjunction, where the sperm cell’s division during conception results in the additional Y chromosome.

Physical Characteristics of XYY Syndrome

The physical features associated with XYY syndrome can vary greatly from individual to individual. Not all boys born with this condition will exhibit observable differences. The physical characteristics are a result of the interaction between an individual’s genotype (their unique genetic makeup) and environmental factors, which together determine the phenotype (the physical expression of the genes).

Some physical features that may be associated with XYY syndrome include:

• Larger than average testes
• Increased distance between two body parts, typically
• Larger head size

Diagnosing XYY Syndrome: Prenatal and Postnatal Approaches

Since there is often no medical reason to test for XYY syndrome, the diagnosis is commonly never made. However, there are several ways in which the condition can be identified:

1. Prenatal diagnosis: XYY syndrome can be detected before birth through amniocentesis, which involves gathering a sample of the fluid surrounding the fetus, or chorionic villus sampling (CVS), where tissue samples are taken from the placenta.
2. Postnatal diagnosis: If prenatal diagnosis is not done, a physician can diagnose XYY syndrome through a clinical evaluation, patient history, and specialized tests, such as a karyotype, which is the most common test used to detect the presence of an extra Y chromosome.
3. Diagnosis due to learning, developmental, or behavioral issues: Boys may also be diagnosed with XYY syndrome if they exhibit learning problems, developmental delays, or behavioral issues.

Prognosis and Outcomes for Individuals with XYY Syndrome

Individuals with XYY syndrome can generally expect a good long-term outlook. Many boys with the condition can do well in school and build healthy relationships, while adults with the syndrome often have successful careers and families.

It’s important to note that the severity of symptoms and the overall prognosis can vary from person to person, as the interaction between an individual’s genotype and environmental factors plays a crucial role in their development and life outcomes.

Comparing XYY Syndrome to Other Chromosomal Conditions

While XYY syndrome is a unique chromosomal condition, it is important to draw comparisons to other similar conditions to gain a broader understanding of the genetic complexities involved.

For example, Turner syndrome is a condition in which a female is missing all or part of one X chromosome, while Triple X syndrome is a genetic disorder in which a female carries an extra X chromosome in each of her cells.

Understanding the similarities and differences between these chromosomal conditions can provide valuable insights into the underlying genetic mechanisms and the potential implications for individuals affected by these rare disorders.

Addressing the Importance of Awareness and Support

Despite the relatively low prevalence of XYY syndrome, it is crucial to raise awareness about this condition and the unique challenges faced by individuals and their families. By increasing understanding and access to educational resources, healthcare professionals, and support networks, we can ensure that those affected by XYY syndrome receive the appropriate care and guidance they need to thrive.

Empowering individuals with XYY syndrome and their loved ones with knowledge and support can positively impact their quality of life, educational outcomes, and overall well-being, ultimately leading to more fulfilling and successful life experiences.

What Is XYY Syndrome? Symptoms, Causes, Diagnosis, Treatment, and Prevention

How Is XYY Syndrome Diagnosed?

Since there is often no medical reason to test for XYY syndrome, the diagnosis is commonly never made.

With that said, a diagnosis can be made before birth while a baby is still in the mother’s womb with amniocentesis, which involves gathering a sample of fluid that surrounds the fetus or through chorionic villus sampling (CVS), the removal of tissue samples from a portion of the placenta. (3)

These tests can reveal if an extra Y chromosome is present.

If prenatal diagnosis is not done, a physician can diagnose XYY syndrome on a person by performing a clinical evaluation, patient history, and specialized tests, such as a karyotype, which is the most common test, to detect the presence of an extra Y chromosome. (3)

Boys may also be diagnosed because of learning problems, developmental delay, or behavioral issues. (3)

Prognosis of XYY Syndrome

Those with XYY can expect to have a good long-term outlook. Boys can do well in school and in building relationships, while adults with the syndrome can have successful careers and families. (4)

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What Are YY Chromosomes? When Superman Syndrome Occurs

Written by WebMD Editorial Contributors

• What Causes YY Chromosomes to Occur?
• What Are the Physical Characteristics of YY Chromosomes?
• What Are the Symptoms of YY Chromosomes?
• How Is YY Diagnosed?

‌Although genetics are hereditary, a phenomenon in genetic alterations occurs when male babies receive an extra Y chromosome in each of their cells, resulting in an XYY combination. The syndrome is commonly known as Jacob’s syndrome, Superman syndrome, XYY karyotype, XYY syndrome, YY syndrome, and 46,XY/47,XYY mosaicism. The genetic alteration occurs in one out of 1,000 male babies and can be traced back 100,000 years to one male ancestor.

The usual number of chromosomes inside every cell of your body is 46 total chromosomes, or 23 pairs. You inherit half of your chromosomes from your biological mother, and the other half from your biological father.

The first 22 pairs of chromosomes are called autosomes. The 23rd pair of chromosomes are known as the sex chromosomes, because they decide if you will be born male or female. Females have two X chromosomes, while males have one X and one Y chromosome. 

The Superman syndrome occurs when males receive an extra Y chromosome at conception, creating an XYY combination. ‌This results in a male baby born with the XYY syndrome, which is a random occurrence due to the sperm cell’s formation before conception occurs. ‌

Known as nondisjunction, this is an error in the sperm cell’s division. The resulting child will have an extra Y chromosome in every cell of his body. However, it’s not a hereditary trait — fathers with XYY chromosomes don’t pass on this syndrome to their sons.

The physical characteristics in a person with an extra Y chromosome have broad variations. It’s important to remember that not all boys born with XYY syndrome will demonstrate observable differences. How your physical body functions is a result of the instructions encoded in your genes. You have an inherently unique genetic makeup that creates your genotype.‌

Your genotype combines with environmental factors to determine your physical body structure and function known as the phenotype. The entire embodiment of a full set of chromosomes results in your karyotype.‌

Physical features associated with this syndrome may include:

• Large testes 
• ‌Large head 
• Increased distance between two body parts, typically the eyes
• Increased belly fat
• Large teeth
• Flat feet 
• Fifth fingers that curve inward
• Atypical side-to-side curvature of the spine 
• Tall stature ‌

It’s important to keep in mind that sometimes there’s an absence of any unusual phenotype traits, although above-average height is a common result. Studies reveal that men with the syndrome carry an extra copy of the SHOX gene, which is found on a sex chromosome. The SHOX gene is also responsible for skeleton development, particularly in the growth and maturation of the limbs.‌

A majority of men with XYY syndrome are fertile, with typical testosterone levels and sexual development. However, some boys may develop testicular failure that leads to fertility problems.

The XYY syndrome correlates with certain physical conditions and disabilities in males with the extra Y chromosome. Symptoms range from mild to severe, so the physical symptoms can go undetected:

• Asthma
• ‌Autism spectrum disorder
• Seizures 
• Hand tremors
• Involuntary movements
• Low muscle tone hypotonia
• Delayed development of motor skills (such as sitting and walking)
• Speech delay
• Difficulty with reading and writing
• Dental problems
• Autism spectrum disorder (mildly)
• Attention deficit disorder, ADHD
• Anxiety 
• Mood disorders
• Depression
• Infertility

‌It’s important to note that intellectual disabilities are not a typical sign. Individuals with XYY syndrome are also able to produce children with typical karyotypes.

Genetic testing for XYY syndrome can be conducted in prenatal tests or anytime throughout the boy’s life. Upon diagnosis, the syndrome can be managed through specialized education and therapies, such as when developmental delays in speech and mobility are apparent. Two commonly ordered tests are:

1. Karyotype test, which detects all the chromosomes in a cell
2. Chromosomal microarray test, which detects extra or missing chromosomes

There are also prenatal tests that can confirm a diagnosis of the XYY syndrome, such as an amniocentesis or chorionic villus sampling, which pregnant women can have to detect potential genetic problems with their unborn child. It’s speculated that a portion of the male population who have Jacob’s syndrome never receive diagnosis due to the lack of symptoms.

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Jacob’s syndrome – XXY

XYY-syndrome is a chromosomal disease that is characteristic only for men. The carrier of the syndrome has an additional Y-chromosome, the total chromosome set is 44 autosomes and three sex chromosomes. Outwardly, males with an extra Y chromosome usually do not have significant differences from normal ones, but they may have a number of features.

Find out with 99% accuracy about the risk of Jacob’s syndrome and other chromosomal abnormalities, as well as the sex of the fetus, from 9weeks of pregnancy, just donating blood from a vein. Learn more about the NIPT test.

Signs of Jacob’s Syndrome

The presence of a second Y-chromosome in most cases does not lead to any physical abnormalities. At the same time, many men with XYY syndrome have one or more features. They are of normal height at birth, but often grow faster during childhood. On average, as an adult, the carrier is higher than 75% of men of the same age. Some men with XYY syndrome have slight incoordination that can make them appear clumsy. Fertility is most often not impaired, usually such men are heterosexual and have normal sexual function. Nevertheless, cases of a significant decrease in fertility, up to infertility, are described. A small number of carriers also have elevated levels of sex hormones associated with spermatogenesis, which can lead to infertility due to impaired sperm production. It is not known how high the incidence of infertility in men with XYY syndrome is. IQ is within the normal range, but often slightly lower than that of siblings. Approximately half of the carriers have learning problems, in particular, there may be speech and reading disorders. There may be an increased risk of behavioral problems such as hyperactivity disorder, men with XYY syndrome are often impulsive and emotionally immature.

Prenatal diagnosis

1) Invasive tests (amniocentesis, chorionic biopsy) are mainly indicated for women who have an increased risk of having a baby with Jacob’s syndrome, for example, patients whose age is over 35 years or with poor results of non-invasive tests: ultrasound and tests. Invasive diagnostic methods are highly accurate, however, given the risk of complications, they are not suitable for mass conduction by all pregnant women, but are carried out only for special indications.

2) Non-invasive technologies so-called screenings. Screening is a comprehensive study of pregnant women for the presence of chromosomal abnormalities in the fetus. Several signs have been identified that indicate a high risk of the presence of the disease, which can be detected by ultrasound of the fetus (absence of the nasal bone, increased thickness of the collar space, insufficient length of the femur and humerus, and other features). In combination with ultrasound, there is a biochemical analysis of the mother’s blood for hormones such as free beta-hCG and PAPP-A. The obtained data on biochemical markers are analyzed in conjunction with the results of an ultrasound examination, and the result of the entire screening is a calculation of the risk of having a chromosomal abnormality in the fetus.

However, when using standard tests for Jacob’s syndrome, only 3% of women referred for invasive diagnosis actually confirm the presence of the disease. At the same time, false-negative results are not excluded, when screening shows a low risk, and the child is born with a chromosomal pathology.

Non-invasive examination method (NIPT test)

• 99% accuracy, which is much more accurate than classical diagnostics (ultrasound and biochemical screening)
• is completely safe, unlike invasive methods – to take material for analysis, you just need to take blood from a vein of a pregnant woman.
• in early pregnancy: the test can be performed as early as the 9th week of pregnancy.

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Extra X and Y chromosomes – NIPT Prenetics

Contents

Genetic information is contained in each cell in the form of formations located in the nucleus – chromosomes. At the same time, a person has a double (diploid) set, that is, the karyotype is represented by 23 pairs of chromosomes, and the chromosomes themselves are normally 46.

The normal chromosome formula can be written as 44+XX or 46(XX) for women and 44+XY or 46(XY) for men. 44 chromosomes or more correctly 22 pairs – autosomes – they are the same for both sexes, and the 23rd pair is called sex chromosomes, since they determine the sex of the unborn child.

If the 23rd pair is XX, then the gender is female, if XY, then male.

Changes in the total number of chromosomes, or normal karyotype, are called aneuploidies. Chromosomes may be larger or smaller than normal.

Types of aneuploidies

Autosomal

Changes in the number of autosomes occur in different pairs of chromosomes. Most often, trisomy occurs in the following pairs of chromosomes, that is, situations where instead of two chromosomes there are three. Trisomy 21 is Down syndrome, trisomy 18 is Edwards syndrome, and trisomy 13 is Patau syndrome. These types of chromosomal pathologies can be combined with the birth of a live fetus, but with multiple severe malformations, and trisomy 18 and 13 are characterized by very poor survival of such children, and trisomy 21, despite developmental malformations, allows a person to live a fairly long time. Information on the main trisomies is in the relevant articles on our website.

In general, there are much more aneuploidies in autosomes – they can also occur in other pairs of chromosomes, tetrasomies or combinations of trisomies in several pairs at the same time are much less common, but they are all fatal, and even at the earliest stages of pregnancy, spontaneous termination occurs.

Extra X and Y chromosomes in pair 23

Extra chromosomes in pair 23 or extra sex chromosomes form the characteristic clinical signs, however, according to the degree of their manifestations, additional sex chromosomes are accompanied by much milder defects. At the same time, albeit very rarely, tetra-, penta- and more chromosomes can occur, which leads to an increase in the severity of developmental defects.

The most common variants of additional Y and X chromosomes will be considered below.

XXY syndrome – Klinefelter’s syndrome

In addition to this classic variant, there are other more rare combinations with an increase in X and Y chromosomes.

This syndrome of aneuploidy for sex chromosomes is characterized by a violation of the development of the male body in the direction of its feminization, that is, with a predominance of female features. It is important that before the onset of puberty, in some cases, it may not be recognized at all, it can only be suspected by a number of indirect signs.

After the onset of puberty, the manifestations become characteristic – high growth, while the female type of figure with a wide pelvis and narrow shoulders. The voice can remain practically unchanged – it does not mutate, does not become masculine. Characteristic is the underdevelopment of the external genital organs and erectile dysfunction. At the same time, female-type hair growth is noted. There is a lower level of libido in such men, very often infertility occurs due to impaired development of spermatozoa. In the intellectual sphere, some lag is possible.

XYU syndrome — “superman” syndrome

Despite the name, such people do not have any superpowers, as well as excessive aggression and excessive potential in the intimate sphere.

The main features are shorter stature and earlier onset of puberty. Masculinization occurs earlier than among peers, excessive hair growth and earlier baldness are more common. In the intellectual sphere, there is a slight lag behind the population, but this is due to the fact that such children from early childhood have increased distractibility, lability of attention, restlessness, they learn the material more difficult, it is from school that the specified lag is observed. There may be some decrease in the ability to conceive. Although the vast majority of patients with XY syndrome are not detected clinically, but with various genetic tests, that is, “in passing”

Syndrome XXX – “superwoman” syndrome

Similar to the previous one, it can be an “accidental finding” during genetic studies, outwardly it has minimal manifestations.

Of the most pronounced – a slight decrease in the ability to bear, due to a higher percentage of spontaneous interruptions, minimal manifestations in the reproductive and intellectual spheres can be observed.

Additional Y and X chromosomes with minimal manifestations

In this case we are talking about the so-called “mosaicism”. This is a phenomenon when a certain part of the cells of the body contains some kind of aneuploidy, and the rest of the cells are described by a normal chromosome formula. This situation occurs if the chromosomal mutation did not occur during the fertilization of the egg, but in the early stages of zygote division. The later this happens, the smaller part of the cells has karyotype disorders and the less clinical manifestations. Very often, such mosaicism is found only in genetic studies.

Diagnosis of various types of aneuploidy.

The only reliable way of early intrauterine diagnosis of chromosomal abnormalities in the fetus is a genetic study. Confirmation of the diagnosis, suspected on the basis of the risks identified during screening, is carried out with an invasive sampling of material, which requires clearly justified indications for carrying out.

With the help of the non-invasive prenatal test Prenetix, it is possible to examine fetal DNA in the venous blood of the expectant mother from the 10th week of pregnancy. The reliability and specificity of the method allows us to classify Prenetix as an expert-level screening, which significantly increases the information content of traditional first trimester screening.