What Is Klinefelter Syndrome?

The group of symptoms with Klinefelter Syndrome was first described in 1942 by Dr. Harry Klinefelter and his coworkers. In the late 1950s other researchers indicated that males with these specific symptoms had an extra X chromosome (XXY) instead of the usual XY configuration found in males.

It appears from studies that the XXY chromosome arrangement is one of the most frequently seen genetic chromosomal variation found in humans, occurring in as many as 1:500 to 1:1000 live male births. An outstanding trait of the XXY population is the wide variability of physical characteristics and symptoms. Some show no abnormalities at all.


For those XXY's who develop Klinefelter Syndrome, typical characteristics and symptoms include:

  • Tall stature
  • Rounded body type
  • Hand tremors
  • Enlarged breasts (gynecomastia)
  • Underdeveloped muscles
  • Small testes or hypogonadism
  • Sparse facial and body hair
  • Sterility (inability to produce live sperm)
  • Overweight
  • Level of activity and endurance lower than others their age
  • Restless sleep patterns, but hard to awake in the morning
  • High-pitched voice
  • Lowered self-esteem
  • Difficulties in social situations (shy, passive, apathetic, sensitive, dependent, more immature and less confident than others their age)
  • Good spatial thinking capacities
  • Creative and artistic way of thinking
  • Learning difficulties
  • Expressive speech and language problems (difficulties putting ideas and thoughts into words) with near-normal understanding of what is said (near normal receptive language skills)
  • Difficulty recalling what was just heard (decreased immediate auditory recall)
  • Difficulty learning to read and write
  • Tendency to withdraw when presented with difficult material (may result in the child falling behind in the curriculum)
  • Emphatic disposition
  • Frustrated with behavorial outbursts
  • Well behaved in the classroom - cooperative and eager to please the teacher


Because XXY's often times don’t look any different from others, many remain undiagnosed their entire lives. Of course, for those who develop Klinefelter Syndrome, it is beneficial for the child to be diagnosed as soon as possible so that the learning disabilities and behavioral issues can be addressed and managed early on.

The earliest a child can be identified as having XXY is prior to birth. With the use of an amniocentesis or chorionic villus sampling (CVS), the chromosome variation can be detected. If, however, prenatal testing was not considered, the child may not be diagnosed until beginning school, where the child begins to show a delay in language skills and difficulty with reading and writing. If at that point Klinefelter Syndrome is considered, a simple blood test can confirm the syndrome.


There is no cure for Klinefelter Syndrome, therefore, treatment is symptomatic. Regular injections of the male hormone, testosterone, beginning at puberty, can have positive effects on many of the symptoms if the child is supposed to develop as male. Otherwise, estrogen is applicable. In some cases, for those who have developed excessive breast tissue, surgery may be required. As many children with Klinefelter Syndrome have speech and language difficulties, it may also be helpful to work with a speech pathologist.

In terms of the child’s education, XXY's with Klinefelter Syndrome are typically well behaved in the classroom and are eager to please the teacher. However, if they are presented with material that they find difficult, they tend to withdraw. If it goes unnoticed by the teacher, the child may fall behind in the curriculum and may need to be held back a grade. Therefore, it is important, for the success of the child, to be in a small classroom where he can receive sufficient individual attention from the teacher. The child’s chances of success are even greater if the parents and school cooperate to form an individualized education plan and provide related services if necessary.

What to Expect

The adolescent years can be difficult. XXY boys with Klinefelter Syndrome tend not to be as strong or as athletic as other boys. This lack of strength and agility, combined with learning disabilities may damage self-esteem. Counseling in the adolescent years, therefore, may be necessary.

Little is known about adults with Klinefelter Syndrome. One study in particular, however, found that those with Klinefelter Syndrome were more likely to have scholastic failure, depression and other psychological problems, as well as a lack of energy and enthusiasm. However, by the time many reached their forties, most had overcome their problems. The majority of XXY's also reported that their energy and activity levels had increased, that they were more productive on the job, and that their relationships with other people had improved. The study also revealed, however, that XXY's with Klinefelter Syndrome were less likely to have been married than typical males.

Generally speaking, it is expected that if the children with Klinefelter Syndrome receive appropriate intervention, such as counseling and hormone supplements, in the early years, they can live a very full and productive life.