Klinefelter Syndrome
Definition
Klinefelter syndrome is a condition caused by one or more extra X chromosomes
in males. It is the second most common health condition
caused by an extra sex chromosome. Klinefelter syndrome is named for
Dr. Harry Fitch Klinefelter (1912
General Hospital in Boston, who first described it in 1942. The
genetic cause of the syndrome was not discovered until 1959.
–1990), an endocrinologist at Massachusetts Description
Many men with an XXY chromosome arrangement tend to be taller than
their father or brothers, to have a rounded body type with a tendency tobe overweight, to develop enlarged breasts resembling those of a woman,
to have a smaller than average penis and testicles, and to lack facial or
body hair. On the other hand, many other men who are XXY do not
develop these features; some live out their lives without ever knowing
that they have an extra X chromosome. For this reason, many doctors
no longer use the term
males with the extra chromosome simply as
“Klinefelter syndrome” but prefer to describe“XXY males.” Demographics
Klinefelter syndrome affects only males. It is thought to occur in one in
every 500year in the United States. The rate of Klinefelter
syndrome is five to twenty times higher in boys
with mental retardation than in the general
population of newborns. It appears to be equally
common in all races and ethnic groups.
Causes and Symptoms
Klinefelter syndrome is caused by a type of
genetic error called nondisjunction. Ordinarily,
the process of cell division that leads to the formation
of germ cells (sperm and eggs) results in a cell
with only half the number of chromosomes
— twenty-three, instead of forty-six. In nondisjunction,
the division of sex chromosomes does not
occur, resulting in either an egg with two X chromosomes
or a sperm with both an X and a Y
chromosome. If a normal sperm carrying a Y sex
chromosome fertilizes an egg with two Xs, or a
sperm carrying both an X and a Y chromosome
fertilizes a normal egg, an XXY male will be conceived.
According to researchers, about half the time the extra chromosome
comes from the baby
the mother. A mother who is thirty or older has a slightly increased risk
of having an XXY son.
Klinefelter syndrome is characterized by a range of psychosocial as
well as physical problems. Not all XXY males will have all these difficulties,
and many have them only in mild form.
’s father and the other half of the time from •
levels of male sexual hormones.
Smaller than normal testes and penis, with lower than normal •
Thin or absent body and facial hair. •
High-pitched voice. •
adolescence.
Rounded body shape, enlarged breasts, rapid weight gain in •
speech, difficulty paying attention, mild difficulties with shortterm
memory, and problems with learning to read.
Developmental and learning disabilities. These include delayed• •
with disproportionately long arms and legs.
Taller than average height after puberty •
XXY males are at increased risk of certain
autoimmune disorders, including rheumatoid
arthritis and lupus. They are also at increased
risk of breast cancer and osteoporosis.
Infertility (inability to father children). Diagnosis
Diagnosis of Klinefelter syndrome depends in
part on the severity of the patient
As has been noted, many XXY males are only
mildly affected by their extra X chromosome and
may never be diagnosed. Although babies can be
diagnosed with the syndrome before birth, the
two most common symptoms that bring XXY
males to the doctor
enlarged breasts and infertility, both of which
become matters of concern after puberty. Some
XXY boys are diagnosed during the elementary
school years because they have speech problems
and other learning difficulties.
The diagnosis is made by taking a karyotype,
or chromosome test. To perform a karyotype,
the doctor takes a small sample of the
patient
and cultured in a special solution and
examined under a microscope to see what the
chromosomes look like.
The doctor may also test a sample of blood
for hormone levels. XXY males have low levels
of testosterone, a male sex hormone, in their
blood serum.
’s symptoms.’s office for testing are’s blood. The white blood cells are isolated Treatment
Treatment of Klinefelter syndrome may involve an educational evaluation
as well as medical treatment:
•
are given to XXY males, preferably beginning at puberty, in orderto help them gain muscle strength, develop facial hair and a deeper
voice, enlarge the testes, raise overall energy levels, and protect
against osteoporosis. In many cases hormone treatment improves
the boy
’s mood and self-esteem as well. •
surgery to remove the extra breast tissue. Surgical treatment
reduces the man
of social embarrassment.
Surgery. XXY males with noticeably enlarged breasts may have’s risk of breast cancer as well as removing a cause •
that XXY boys have a complete educational evaluation, preferably
in elementary school, so that their learning difficulties (if any) can
be treated before they develop behavioral problems or become
depressed.
Speech therapy and language therapy. Most doctors recommend •
them improve their muscle strength and coordination.
Most doctors consider mid-to-late adolescence the best time to tell
an XXY boy about his condition. At that age most are able to understand
the cause of the syndrome and its implications, and to decide whether
they want to share the information with anyone else.
Physical therapy. Some XXY boys benefit from exercises that help Prognosis
Most XXY males can live productive lives with normal life expectancy;
many complete college and graduate school. In 1996 a technique was
developed for extracting sperm from the male testicle and injecting it
into a female egg; since that date, at least sixty children around the
world have been conceived and born using sperm from men with Klinefelter
syndrome. Men who are able to father children this way do not
have any greater risk of producing an XXY son than men in the general
population.
Prevention
There is no known way to prevent Klinefelter syndrome because it is
caused by a random genetic error.
The Future
It is unlikely that Klinefelter syndrome will become more common in the
general population in the future because nondisjunction is a randomgenetic error. What is likely, however, is that earlier diagnosis and better
understanding of the syndrome will help XXY males do well in school
and the adult workplace and lower their risk of depression and other setbacks.
The knowledge that most XXY males benefit from hormonal
treatment, surgery, and various supportive educational measures and can
have normal lives is certainly encouraging.
SEE ALSO
Breast cancer; Lupus; Osteoporosis; Rheumatoid arthritis For more information
BOOKS
Bock, Robert.
Their Families
and Human Development, 2006.
Morales, Ralph.
Syndrome
Understanding Klinefelter Syndrome: A Guide for XXY Males and, rev. ed. Bethesda, MD: National Institute of Child HealthOut of Darkness: An Autobiography: Living with Klinefelter. Louisville, KY: Chicago Spectrum Press, 2002. PERIODICALS
Brody, Jane.
“Personal Health: The Havoc of an Undetected Extra Chromosome.” New York Times
nytimes.com/gst/fullpage.html?res=9504EEDD1731F932A0575BC0A9629C8B63
(accessed April 6, 2008).
, August 31, 2004. Available online at http://query. WEB SITES
American Association for Klinefelter Syndrome Information and Support
(AAKSIS).
at http://www.aaksis.org/Documents2/Klinefelter_Brochure_.pdf (accessed
April 6, 2008).Brager, David.
“I’m Not Fat, I’m Deformed: Klinefelter’s Syndrome & Me.” David Brager
klinefel.html (accessed April 6, 2008). This is one man
of his life before and after his diagnosis.
Genetics Home Reference.
condition=klinefeltersyndrome#resources (accessed April 6, 2008).
Knowledge Support and Action (KS&A).
genetic.org/knowledge/support/action/199/ (accessed April 6, 2008). KS&A
is a nonprofit organization that was formed in 1989 to help people born with
extra X or Y chromosomes. This portion of the KS&A website contains basic
information about Klinefelter syndrome as well as links to articles, research
reports, and other materials related to the condition.
National Human Genome Research Institute (NHGRI).
SyndromeWORDS TO KNOW
Androgen: The generic term for the group of male
sex hormones produced by the body.
Germ cell: A cell involved in reproduction. In
humans the germ cells are the sperm (male) and
egg (female). Unlike other cells in the body,
germ cells contain only half the standard number
of chromosomes.
Karyotype: A photomicrograph of the chromosomes
in a single human cell. Making a karyotype
is one way to test for genetic disorders.
Nondisjunction: A genetic error in which one or
more pairs of chromosomes fail to separate during
the formation of germ cells, with the result that
both chromosomes are carried to one daughter
cell and none to the other. If an egg or sperm with
a paired set of chromosomes is involved in the
conception of a child, the child will have three
chromosomes in its genetic makeup, two from
one parent and one from the other.
Testosterone: The principal male sex hormone.’s Homepage. http://www.geocities.com/dibragerowtcom/’s personal accountKlinefelter Syndrome. http://ghr.nlm.nih.gov/Klinefelter Syndrome. http://www.Learning about Klinefelter. http://www.genome.gov/19519068 (accessed April 6, 2008).A Guide to Klinefelter Syndrome. Available online in PDF formatHormone injections. Injections of androgens (male sex hormones)Depression and emotional distress caused by low-self-esteem.
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