Klinefelter syndrome (KS) occurs in some men who have more than one X chromosome (XXY).
Copyright © Nucleus Medical Media, Inc.
Males usually inherit a single X chromosome from their mother and a single Y chromosome from their father. Males with KS get at least one extra X chromosome.
A risk factor is something that increases your chance of KS. Women over age 35 may have a slightly increased chance of having a child with KS. There are no other known risk factors for this disorder.
XXY occurs in approximately 1 out of 580 live male births, but many men with it do not develop KS. When KS does develop, it usually goes undetected until puberty or sometimes much later.
Characteristics may include: For babies:
Smaller birth weight and slower muscle and motor development
For children and adults:
Small firm testes, small penisAbnormal body proportions (long legs, short trunk)Tallness with extra long arms and legsSocial and learning disabilities (common)Personality impairmentAttention deficit hyperactivity disorder
(ADHD)Speech and language problems—Children with KS often learn to speak later than other children do. They may have a difficult time reading and writing.Normal to borderline IQLack of ability to produce sperm (common)Lack of facial and body hairEnlarged breasts (common)Diminished sex drive, sexual dysfunction
Men with KS have an increased risk of: Type 2 diabetesBreast cancerLung cancerCardiovascular diseaseLung diseaseOsteoporosisHypothyroidismDental problemsLeg ulcers
A test called a karyotype is used to diagnose KS. In the case of KS, there are usually 47 chromosomes rather than the normal 46.
Many men with XXY do not know they have the condition. The diagnosis may be found:
In babies— with
or very small penis
In children—when the child is having problems learningIn adolescents—when the child has delayed puberty or excessive breast development
In adults—when the man has
Treatment of KS includes:
The main treatment is testosterone . When boys with KS are 10-12 years old, their hormone levels are checked yearly. If testosterone levels are low, then treatment may be helpful. Men diagnosed may also benefit from taking the hormone. However, testosterone cannot reverse infertility.
The benefits of testosterone include: Increased strengthMore muscular, male appearanceGrowth of facial and body hairBetter self-esteemModulation of moodIncreased energyIncreased ability to concentrateGreater sex driveImproved bone density
This therapy should begin in early childhood to avoid social and school learning problems. Treatment may involve: Speech therapySpecial education servicesExtra support and help with learning from parents and teachersSocial skills training and psychological counseling
Currently, there are no known ways of preventing KS.
Klinefelter syndrome. EBSCO DynaMed website. Available at:
http://www.ebscohost.com/dynamed. Updated February 28, 2013. Accessed October 11, 2011.
Tell me about 47, XXY. Klinefelter Syndrome and Associates website. Available at:
http://www.genetic.org/knowledge/support/action/199/#Brief%20Introduction%20to%20Klinefelter%20syndrome. Accessed August 20, 2013.
Klinefelter syndrome: overview. National Institute of Child Health & Human Development website. Available at:
Updated April 3, 2013. Accessed August 20, 2013.
Last reviewed August 2013 by Kari Kassir, MD; Michael Woods, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
Copyright © EBSCO Publishing. All rights reserved.