All Children's Hospital Logo

Health Information Library

Parents > A to Z > X > A to Z: XXY Syndrome
A to Z: XXY Syndrome

A to Z: XXY Syndrome

May also be called: Klinefelter Syndrome; XXY Condition

XXY syndrome, also called Klinefelter syndrome, is a fairly common genetic condition found only in males that happens when a boy is born with an extra sex chromosome in most or all of his cells.

More to Know

Genetic material, or DNA, is contained in tiny structures called chromosomes that are found inside the body's cells. A person's gender is determined by the sex chromosomes: females have two X chromosomes, or XX; most males have one X chromosome and one Y chromosome, or XY. Males with XXY syndrome are born with cells that have an extra X chromosome, or XXY. This can cause delayed development and puberty, a smaller penis and testicles, infertility, and other symptoms.

The condition that causes XXY syndrome is present at birth and can't be changed, but educational treatments and various types of therapy (physical, speech, behavioral, mental health, and occupational) can help boys keep pace in school and overcome problems with shyness and social development.

Keep in Mind

Kids and teens with XXY syndrome sometimes have trouble fitting in with kids their own age. With early intervention, in adulthood most will have normal social relationships with friends, family members, coworkers, and others.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.

Related Articles
P    All About Genetics
T    Delayed Puberty
K    Growth Disorders
T    The Basics on Genes and Genetic Disorders
K    What Is a Gene?
K    Word! Chromosomes
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
© 1995-2015 KidsHealth® All rights reserved. Images provided by iStock, Getty Images, Corbis, Veer, Science Photo Library, Science Source Images, Shutterstock, and

Additional Info

Pocket Doc Mobile App
Maps and Locations (Mobile)
Programs & Services
For Health Professionals
For Patients & Families
Contact Us
Find a Doctor

All Children's Hospital
501 6th Ave South
St. Petersburg, FL 33701
(727) 898-7451
(800) 456-4543

Use Normal Template
© 2015 All Children's Hospital - All Rights Reserved