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47,XYY Syndrome

By

Nina N. Powell-Hamilton

, MD, Sidney Kimmel Medical College at Thomas Jefferson University

Last full review/revision Jun 2020| Content last modified Jun 2020
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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.

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