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Klinefelter syndrome (men or woman?)

Klinefelter syndrome is a very specific health condition with extra female chromosome (so called “XXY syndrome”) – condition that occurs in men who have an extra X chromosome. Boys with XXY chromosomes are often taller than other boys their age and they could have more fat around the belly. Persons with XXY are usually infertile.

This syndrome was described by Dr Harry Fitch Klinefelter in 1942 and later in 1950s researchers discovered that clients with Klinefelter syndrome had extra sex chromosome thus having the pattern “XXY”.

Healthy males have 2 chromosomes (XY) – “X” inherited from mother and “Y” inherited from father. Healthy females also have 2 chromosomes (XX) – one “X” received from mother and second “X” received from father. Persons with Klinefelter syndrome have additional “X” chromosome (in total “XXY”) – it is inherited chromosome disorder. This syndrome affects testicular growth and could lead to reduced production of main male hormone testosterone. XXY syndrome can be recognized by reduced muscle mass, limited masculine body and facial hair and enlarged breasts.

Klinefelter syndrome is rare condition – it occurs in one of every 450 male babies. According to health experts, some men live with this syndrome without knowing of its existence.

Klinefelter syndrome causes

This syndrome occurs as a result of random genetic error when additional “X” chromosome attaches to male “XY” chromosome. Additional copies of genes on extra X chromosome can interfere with male sexual development and fertility.

Scientists don’t know why this random error happens – they couldn’t identify any factor which can trigger chromosome “mistakes”. At the same time, it was noted that older mothers have higher risks.

Klinefelter syndrome symptoms

Klinefelter syndrome

Symptoms can vary widely in different persons and they can change with aging. Some males experience typical symptoms early during adolescence and some men never even realize they have chromosome disorder. Klinefelter syndrome can be identified during teenage years when puberty comes later, not quite finish or not happen at all. Most common symptoms include the following:

  • Increased breast size called “gynecomastia” (larger breasts compared with boys of same age);
  • Late appearance of body and facial hair (lack of facial, pubic and underarm hair);
  • Taller than family members;
  • Longer limbs (arms and legs), wider hips and shorter torso, disproportionately long arms and legs compared to the length of the body;
  • Poor muscle development, weaker muscles and less muscle tone;
  • Weak bones;
  • Unexplained weight gain (mainly on stomach and/or trunk);
  • Learning difficulties (problems in language learning, trouble listening, difficulty in concentrating);
  • Smaller penis and testicles (compared with boys of same age group);
  • Decreased levels of main male hormone testosterone;
  • Lower energy and reduced sex drive;
  • Behavioral problems (tendency to be shy and sensitive, sadness, lowered mood, depression);
  • Infertility (low sperm count or no sperm).

Klinefelter syndrome diagnosis

Genetic blood test (chromosome karyotype analysis) can easily identify “XXY” syndrome.

Hormonal tests demonstrate decreased levels of main male hormone testosterone.

Physical examination discover smaller penis and testicles.

Semen tests identify decreased sperm counts or asospermia (semen contains no sperm).

Klinefelter syndrome adaptation and treatment

Human chromosomes cannot be changed. This syndrome cannot be cured but treatments solutions are available. Main treatment should be started as soon as possible – it includes hormone therapy (testosterone replacement therapy) which can prevent gynecomastia (growing breasts), can correct physical development, strengthen muscles, improve bone density and prevent behavioral problems. Earlier treatment is started, better are results.

Health experts recommend specific counseling and support for mood, social adaptation and mental health.

Modern assisted reproductive technologies (ART) can provide effective solutions in cases of infertility.

In cases of gynecomastia (increased breasts) plastic surgery can be recommended.


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