What is XYY Syndrome?

XYY syndrome is a rare genetic disorder that occurs only to men. This is a chromosomal birth defect caused by the presence of an extra Y chromosome. Usually, people have 46 chromosomes in each cell which includes one X and one Y chromosome. However, men with XYY syndrome have 47 chromosomes due to the presence of two Y chromosomes. The other names of XYY syndrome are 47, XYY syndrome, Jacob's syndrome, XYY karyotype and YY syndrome. About 1 in 1000 men is affected by this condition.

Causes of XYY syndrome

XYY syndrome is caused due to a random error in the cell division. Nondisjunction is the term given to the missegregation of chromosomes due to the error in cell division. The extra Y chromosome occurs from nondisjunction during cell division of sperm cells either before conception or during early embryo development.

Symptoms of XYY Syndrome

Some patients may show no symptoms, while others may develop mild symptoms. Below given are some of the common signs and symptoms of XYY syndrome:

Underweight
Poor muscle tone
Delay in reaching all the milestones
Delayed in development of speech and language skills
Widely spaced eyes
Learning disability
Lower IQ than normal
Severe acne
Behavioral problems like high temper, hyperactive etc.
Involuntary muscle movement
Taller than average height

Diagnosis of XYY Syndrome

Generally, this rare genetic disorder is never diagnosed because one may experience a few or no problematic symptoms. Usually, men with XYY syndrome have normal sexual development and fertility. But in some cases, they may have decreased sperm count with immature sperm cells. Such men are still fertile but may have issues in impregnating their partner. In such cases, a doctor may suggest a chromosome analysis to check for XYY syndrome.

This condition can be diagnosed during the prenatal stage through amniocentesis or chronic villus sampling.