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Understanding Klinefelter Syndrome: What it is, its Cause, Symptoms and Diagnosis – With Pictures

Updated on June 10, 2017

What is Klinefelter Syndrome and what causes it?

Principal physical symptoms observed in males with Klinefelter Syndrome
Principal physical symptoms observed in males with Klinefelter Syndrome | Source

The study of human chromosomes is now one of the most widely researched subjects in the fields of biology and health (disorders and diseases). With the aid of scientific and technological progress, scientists were able to advance complex studies and research on the human chromosomes – which are microscopic elements present at each human cell of the body. For decades of extensive research, scientists have examined chromosomal behavior and its structural pattern. It was during the late 1950’s that scientists discovered an extra chromosome in patients with a certain genetic disorder. This incidence shed a light to a new area of interest; the Chromosomal Aberration or Chromosomal Abnormality. It was discovered then that most cases of genetic disorders are caused by Chromosomal abnormality (structural or number patterns).

Among of the most known genetic disorders caused by chromosomal abnormalities are Down’s syndrome (which is also known as trisomy 21), Turner syndrome and Klinefelter syndrome – which will be the central topic of this article.

Discovery of Klinefelter Syndrome

What is Chromosomal Aberration?

Chromosomal aberration refers to the disruption or to any change in the chromosomal content of a cell. The abnormality is observed either in the structural arrangement or in the number pattern (sequence) of the chromosomes. Chromosomal aberration is the leading cause responsible for genetic disorders. This also plays a great role in evolution.

In 1942, Dr. Harry Klinefelter and his colleagues at the Massachusetts General Hospital in Boston first published a written report of nine men who were observed to have a number of symptoms which was later identified as a type of genetic disorder. These symptoms include atypical enlargement of breasts, less facial and body hair, small testes and low sperm count. This condition which affects only males was later known as Klinefelter Syndrome. In 1959, it was revealed that these men had XXY genotype; an unusual occurrence as compared to genetically normal males who have an XY chromosomal makeup.

How frequent does this condition occur?

What is an Aneuploidy?

An Aneuploidy is the term used to describe the gain or loss of chromosomes/s from the genetically normal number of chromosomes found in each human cell which is 46 (44 autosomes and 2 sex chromosomes).

Klinefelter syndrome which is caused by the addition of X chromosome is one example of Aneuploidy.

The probability of males acquiring an additional X chromosome is about 1 out of every 500 to 1000 newborn males. This condition becomes one of the most frequently occurring chromosomal aberrations. In fact it is the most common aneuploidy of sex chromosome in males. Though a large number of males acquire an additional X chromosome, many of them have not been observed to have developed the syndrome described by Dr. Klinefelter and his colleagues. It has been later revealed that patients with this condition have varied symptoms. Clinical observations have also shown difference on the severity of the symptoms. Medical researchers prefer to use the term XXY condition or XXY syndrome to refer this condition and XXY males to refer the person who has the condition.

Why do other refer this condition as 47,XXY condition?

Did you know…

that chromosomes play a very important role in determining who we are and what we are? Yes! Chromosomes decide whether we are to be a male or a female, our skin complexion, if we are to grow with a blonde or black hair, tall or short and such. A huge job for a very tiny part in each of us!

Normally, we humans have 46 chromosomes found in each of our cell. Twenty-three of these chromosomes we inherit from our mother and the other half we inherit from our father. These 46 chromosomes are comprised of 44 autosomes and a pair of sex chromosomes (X and Y chromosomes). When a pair of X chromosome is formed during cell production, a female baby is born. When it’s an XY chromosome, a male baby is born.

XXY condition is caused by the addition of an extra female sex chromosome (X chromosome) to the actual diploid set of 46 chromosomes (thus, XXY). The addition brings the total number of chromosomes to 47, which is why XXY condition is also known as 47,XXY condition.

What causes the addition of an X chromosome?

The XXY condition is a type of disorder associated with Aneuploidy. This incidence of gaining or losing of chromosome/s is a result from a “nondisjunction” event during cell division. Nondisjunction occurs when chromosomes fail to separate during meiosis. When this happens, one gamete will have an extra chromosome while the other one will be lacking. Under these circumstances, the offspring produce through fertilization by a normal gamete have either an extra chromosome or a missing chromosome.

In XXY condition, nondisjunction occurs during meiosis I in male or either during meiosis II in female. A picture illustrating the nondisjunction incidence during cell division is shown below.


The first illustration shows an X chromosome retained because of a nondisjunction during meiosis I in the male. The incidence resulted to a sperm with a pair of XY chromosome. When this gamete (XY) fertilizes a normal egg (X), an XXY male offspring is conceived.

The second illustration shows an X chromosome retained during meiosis II in the female producing an XX egg. When the XX egg is fertilized by a normal sperm (Y), an XXY male offspring is also conceived.


Symptoms and Variations

The XXY condition can/may cause problems on the physical and cognitive development of the patient. However, these symptoms are not readily apparent after birth. In fact, many of the men and boys who have the condition don’t show any symptoms. These affected individuals may not even have the slightest hint that they have the condition. Also, the symptoms observed vary from one patient to another. Even the severity of the developed symptoms varies significantly.

Principally, the XXY condition affects the physical and cognitive development of the XXY males. These effects – depending on how the people around
(the social environment) attend to the needs of the affected individual – may have a negative impact on the social and personal development of the person who has the condition.

Symptoms caused by XXY condition are commonly observed during childhood, adolescence and adulthood stages undergo by XXY males.

Observed Symptoms

- weak motor skills, infants with the condition usually learn to walk, sit, crawl, stand (and etc.) later than other at their age
- hypogonadism (decreased testicular hormone/low testosterone level)
- they tend to be taller than kids at their age (4-5 years old)
- lacks body and facial hair, less muscular body and develops rounded body shape instead (with broader hips)
-physical symptoms developed during the adolescence stage may retain
- gynecomastia
-micropenis, cryptorchidism or microorchidism
-taller than average, uneven body proportion
- weak language acquisition (includes talking and reading)
- scholastic difficulties (resulted from the history of learning disability; language development)
- inability to express their selves
Social Behaviour
- shy, reserved or socially withdrawn
- low in self-esteem due to physical and cognitive difficulties
- depression, lack of energy and enthusiasm
- disadvantage in learning language may hinder them from being socially interactive
An XXY male developing Gynecomastia (breast enlargement)
An XXY male developing Gynecomastia (breast enlargement) | Source

XXY males also develop higher-risks of obtaining several health problems.These health problems typically and normally affects females. Such health problems include Osteoporosis, breast cancer and autoimmune disorders (i.e. rheumatoid arthritis).

There are also reported cases of XXY condition variants. One is the so called 46,XY/47,XXY mosaic. In this variation, not all cells have the extra X chromosome. The symptoms are also milder as compared to the symptoms observed in XXY males. Another variation is the 48,XXXY condition but this condition is extremely rare (1 in 18,000 to 50,000 male births) and few reports were recorded about this. Symptoms associated with this condition are similar to XXY condition, more severe though. The severity of occurring symptoms is directly proportional to the number of extra X chromosome present in a cell.

Can the condition be cured?

Quick Question: Does the condition be inherited?

No. XXY condition can’t be passed on from family generation down to the next family generation. The only way of developing the condition is when a disjunction occurs during cell division (meiosis) as discussed above.

Like all genetic disorders caused by chromosomal aberrations, the XXY condition can not be cured. Chromosomal variation is irreversible or at least today the method of normalizing chromosomally variant gene/s is beyond the knowledge and ability of human knowledge.

However symptoms caused by genetic and/or chromosomal variation/s can be treated. For XXY condition, principal symptoms can be treated by injecting testosterone (synthetic) to the affected male. Successful submission to regular schedule of testosterone injections will result to significant improvement in strength, muscular development, and growth of body and facial hair. This may also result into improvement on the psychological and social aspects of the affected male. Upon seeing the physical progress induced by the treatment, an XXY male will feel more positive about his appearance; feeling more manly and energetic. This also significantly enhances self-esteem and develops fulfilling disposition. Added result is that, an XXY male will become socially interactive and will start widening his circle of friends.

Each XXY male may respond differently to the treatment, thus the observed development varies to some degree. While few individuals have not benefited, most XXY males have been observed to develop significant improvement.

A small number of cases reported few side-effects thus, it is highly-desirable to ask for the help and assistance of a medical specialist when one is undergoing the hormonal treatment.

How is XXY condition diagnosed?

The condition can be diagnosed during prenatal stage and adulthood. The method used during prenatal diagnosis is called amniocentesis. Through amniocentesis, fetal cells acquired from the fluid surrounding the fetus is checked for chromosomal abnormalities. Another method is called Chorionic Villus Sampling or CVS. The procedure is similar to amniocentesis except it is done during the first prenatal trimester.

The diagnosis is mostly done during adulthood or at least when a person has aged. The procedure involves an analysis of the chromosomes’ karyotype (karyotyping as referred by some) observed from the drawn white blood cells (lymphocytes). The samples are then examined for any chromosomal abnormality.

There are other several methods used to diagnose XXY condition, but the two most common are the methods discussed above.


Information presented in this article were viewed and checked several times to ensure consistency and reliability of facts. Organization of these facts was based on the writer’s knowledge and awareness of the topic and was essentially supplemented with deep-research personally furthered by the writer. All information presented herein is for educational purpose only and thus, should NOT be employed and/or be used for professional medical purposes.

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    • light20 profile imageAUTHOR


      7 years ago from Ozamiz City, Philippines

      Hi kat11

      Your welcome...and thank you...I'm glad.

      I hope your son is doing well...

      Have a good day Kat.

    • kat11 profile image


      7 years ago from Illinois

      I have a young adult son that for the past 3 years have been going through hormonal placement therapy because his estrogen levels are high and testosterone is not there. Currently he is taking shots one in the stomach and one in the hip twice a month. So I understand this hub. i don't know if they have they checked for genetic defects since he has gone away to college. Hub very informative and well written. Thanks for the insight. voted up


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