What Is Klinefelter Syndrome?
Klinefelter syndrome is a fairly common genetic
condition found in males only.
Many boys with Klinefelter syndrome — also known as XXY syndrome
— have no signs or symptoms, and some don't even know they have it until later
in life.
The XXY condition that causes Klinefelter syndrome can't be changed, but medical
treatment and working with therapists can help a boy's development and help lessen
the condition's effects. Even without treatment, most boys with Klinefelter syndrome
grow up to live productive, healthy lives.
What Causes Klinefelter Syndrome?
Boys who have Klinefelter syndrome are born with it. It's also called XXY because
they have an extra X chromosome in most or all of their cells.
Usually, a person has 46 chromosomes in each cell, divided into 23 pairs, which
includes two sex chromosomes. Half of the chromosomes are inherited from the father
and the other half from the mother. The chromosomes contain genes, which determine
an individual's characteristics, such as eye color and height. Boys typically have
one X chromosome and one Y chromosome, or XY, but boys with XXY syndrome have an extra
X chromosome, or XXY.
Klinefelter syndrome is not caused by anything the parents did or did not do. The
disorder is a random error in cell division that happens when a parent's reproductive
cells are being formed.
If one of these defective cells contributes to a successful pregnancy, the baby
will have the XXY condition in some or all of his cells. Some boys will even have
more than two X chromosomes (XXXY or XXXXY, for example), which increases the risk
of severe symptoms and other health concerns.
When a boy is born with the XXY condition in only some of his cells, it's called
mosaic Klinefelter syndrome. Often, boys and men with this condition
can have milder signs and symptoms than others with the XXY condition.
What Are the Signs & Symptoms of Klinefelter Syndrome?
Not all boys with Klinefelter syndrome will have noticeable symptoms. Other boys
can have symptoms that are physically apparent or problems with speech, learning,
and development.
Babies with Klinefelter syndrome typically have weak muscles, reduced strength,
and quiet personalities. They also can take longer to do things like sit up, crawl,
walk, and speak.
Compared with other kids their age, boys with Klinefelter syndrome might have some
or all of these symptoms:
- a taller, less muscular body
- broader hips and longer legs and arms
- larger breasts (a condition called gynecomastia)
- weaker bones
- a lower energy level
- smaller penis and testicles
- delayed or incomplete puberty (some boys won't go through puberty at all)
- less facial and body hair following puberty
What Problems Can Happen?
Klinefelter syndrome typically causes a boy's testicles to grow at a slower rate
than those of other boys. It also prevents the testicles from producing normal amounts
of sperm and the hormone testosterone.
Testosterone affects the way a boy develops both physically and sexually. Low hormone
levels and problems with sperm production make it difficult or sometimes impossible
for a boy with Klinefelter syndrome to father a child later in life.
Many boys with Klinefelter syndrome show symptoms related to their development
of social and language skills. They may have trouble paying attention. A lot of boys
learn to talk late or have trouble using words to express their emotions. They also
can have trouble with things like learning to spell, read, and write.
Socially, they tend to have quiet personalities. They rarely cause trouble and
are often more helpful and thoughtful than other boys. They're often shy and sensitive,
and many are less self-confident and less active than other boys their age.
Most boys aren't likely to have major health problems, but the condition can bring
some other challenges later in life. Klinefelter syndrome puts males at greater risk
of breast cancer, some other cancers,
and some other diseases like type 2 diabetes, varicose veins and problems with blood
vessels, problems with sexual function, and osteoporosis (weak bones) later in life.
Most boys with Klinefelter syndrome can have sex when they become men, usually
with the help of testosterone treatment. However, problems with their testicles prevent
them from making enough normal sperm to father children.
The vast majority of men with Klinefelter syndrome are infertile and can't father
a child the usual way. Options for becoming natural parents are limited, but fertility
researchers are working on new treatments. By the time a child with Klinefelter syndrome
is ready to become a dad, there may be new options available related to the extraction
of sperm from the testicles.