Kleinfelter`s Syndrome

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Klinefelter syndrome is a chromosomal condition in boys and men that can affect physical and intellectual development. Most commonly, affected individuals are taller than average are unable to father biological children (infertile); however the signs and symptoms of Klinefelter syndrome vary among boys and men with this condition. In some cases, the features of the condition are so mild that the condition is not diagnosed until puberty or adulthood, and researchers believe that up to 75 percent of affected men and boys are never diagnosed.

Boys and men with Klinefelter syndrome typically have small testes that produce a reduced amount of testosterone (primary testicular insufficiency). Testosterone is the hormone that directs male sexual development before birth and during puberty. Without treatment, the shortage of testosterone can lead to delayed or incomplete puberty, breast enlargement (gynecomastia), decreased muscle mass, decreased bone density, and a reduced amount of facial and body hair. As a result of the small testes and decreased hormone production, affected males are infertile but may benefit from assisted reproductive technologies. Some affected individuals also have differences in their genitalia, including undescended testes (cryptorchidism), the opening of the urethra on the underside of the penis (hypospadias), or an unusually small penis (micropenis).

Other physical changes associated with Klinefelter syndrome are usually subtle. Older children and adults with the condition tend to be somewhat taller than their peers. Other differences can include abnormal fusion of certain bones in the forearm (radioulnar synostosis), curved pinky fingers (fifth finger clinodactyly), and flat feet (pes planus).

Children with Klinefelter syndrome may have low muscle tone (hypotonia) and problems with coordination that may delay the development of motor skills, such as sitting, standing, and walking. Affected boys often have learning disabilities, resulting in mild delays in speech and language development and problems with reading. Boys and men with Klinefelter syndrome tend to have better receptive language skills (the ability to understand speech) than expressive language skills (vocabulary and the production of speech) and may have difficulty communicating and expressing themselves.

Individuals with Klinefelter syndrome tend to have anxiety, depression, impaired social skills, behavioral problems such as emotional immaturity and impulsivity, attention-deficit/hyperactivity disorder (ADHD), and limited problem-solving skills (executive functioning). About 10 percent of boys and men with Klinefelter syndrome have autism spectrum disorder.

Nearly half of all men with Klinefelter syndrome develop metabolic syndrome, which is a group of conditions that include type 2 diabetes, high blood pressure (hypertension), increased belly fat, high levels of fats (lipids) such as cholesterol and triglycerides in the blood. Compared with unaffected men, adults with Klinefelter syndrome also have an increased risk of developing involuntary trembling (tremors), breast cancer (if gynecomastia develops), thinning and weakening of the bones (osteoporosis), and autoimmune disorders such as systemic lupus erythematosus and rheumatoid arthritis. (Autoimmune disorders are a large group of conditions that occur when the immune system attacks the body's own tissues and organs.)


Symptoms in babies

When present, many of the symptoms of Klinefelter syndrome in young children and babies may go overlooked because they aren’t always obvious — especially because child development can be very individualized. However, you may want to talk with your child’s pediatrician if these symptoms are present and concern you:

a delayed start in learning to crawl or walk

a delayed start in talking

a seemingly quieter, or more passive attitude

Symptoms in young males and teens

The symptoms of Klinefelter syndrome are often most obvious in tween and teen males due to the onset of puberty. It’s important to follow your instincts if you, or they, are worried something is amiss. Some of the symptoms of the Klinefelter syndrome in tween and teens are:

mild dyslexia

issues with paying attention

lowered energy levels

difficulty socializing

delayed puberty, which can include:

a lack of facial or body hair

a higher pitched voice

more fat deposits around the hips and buttocks, creating a rounder lower half of the body

enlarged breasts (gynecomastia)

taller stature than the rest of the family (including long arms and legs)

difficulty increasing or producing muscle tone

smaller testicles

smaller penis

Symptoms in adults

The main symptom in adults is often fertility difficulties — although there are many treatments available for this symptom.

Adult males who only have an extra X chromosome in some of their cells will have milder symptoms. A smaller number of males have more than one extra X chromosome in their cells. The more X chromosomes they have, the more severe their symptoms may be.

Symptoms of more severe Klinefelter types include:

major problems with learning and speech

poor coordination

unique facial features

bone problems


Everyone is born with 23 pairs of chromosomes, or 46 chromosomes in total, inside each of their cells. These include two sex chromosomes, X and Y.

People who are born female have two X chromosomes, XX. These chromosomes give them sexual traits like breasts and a uterus.

People who are born male have one X and one Y chromosome, XY. These chromosomes give them traits such as a penis and testicles.

People with Klinefelter syndrome are born with an extra X, causing their cells to have XXY chromosomes. This happens randomly during conception. About half the time the extra chromosome starts in the mother’s egg. The other half of the time it comes from the father’s sperm.

Some people with the syndrome have more than one extra X chromosome. For example, their chromosome might look like this: XXXXY. Others have different chromosome abnormalities in each cell. For example, some cells might be XY, while others are XXY. This is called mosaicism.

Risk factors

Klinefelter syndrome is caused by an additional X chromosome. This chromosome carries extra copies of genes, which interfere with the development of the testicles and mean they produce less testosterone (male sex hormone) than usual.

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Klinefelter syndrome may increase the risk of:

Anxiety and depression

Social, emotional and behavioral problems, such as low self-esteem, emotional immaturity and impulsiveness

Infertility and problems with sexual function

Weak bones (osteoporosis)

Heart and blood vessel disease

Breast cancer and certain other cancers

Lung disease

Metabolic syndrome, which includes type 2 diabetes, high blood pressure (hypertension), and high cholesterol and triglycerides (hyperlipidemia)

Autoimmune disorders such as lupus and rheumatoid arthritis

Tooth and oral problems that make dental cavities more likely

Autism spectrum disorder


Klinefelter syndrome is a genetic condition that cannot be prevented. It's a random error in the genetic code that happens before birth. This condition is not passed down through a family (inherited) and there is nothing a parent can do to prevent their child from having Klinefelter syndrome.