Merck Manual

Please confirm that you are a health care professional

honeypot link

47,XYY Syndrome


Nina N. Powell-Hamilton

, MD, Sidney Kimmel Medical College at Thomas Jefferson University

Last full review/revision Jun 2020| Content last modified Jun 2020
Click here for Patient Education

47,XYY syndrome is the presence of two Y chromosomes and one X chromosome in a phenotypic male.

The 47,XYY syndrome occurs in about 1/1000 live male births.

Affected boys tend to be taller than average and have a 10- to 15-point IQ reduction compared with family members. There are few physical problems. Minor behavior disorders, hyperactivity, attention-deficit disorder, and learning disorders are more common.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version

Also of Interest