What is it?

Karyotype 47, XYY syndrome, also known as Jacob’s syndrome, refers to a condition which is characterized by an extra sex chromosome. A male is born with 46 chromosomes, two of them are sex chromosomes- X and Y. In this syndrome, there is an extra copy of the Y chromosome. Sometimes, people with this syndrome do not experience any symptoms while others may have learning disabilities, low muscle tone, or simply might be taller. Their sexual development is normal.

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Signs & symptoms

Symptoms may include having an increased growth rate, which is noticeable especially in the ages 3-5, acne, learning disabilities, behavioral problems, and there is a higher rate of attention deficit and hyperactivity disorder.


Diagnosis is based upon findings from medical history and physical examination. Further evaluation may include genetic testing.


Treatment is not always necessary. If there is a need, it may include symptomatic and supportive speech therapy, occupational therapy or assistance for learning disabilities.

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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