XYY syndrome is a condition known as aneuploidy which is a trisomy of the sex chromosomes in which a male has an extra Y chromosome which results in a 47 XYY karyotype. It has been found that most of the sufferers don?t know their karyotype. It has been proved that some 97% of the patients are unaware of their condition.

Generally the chromosomal change will not lead to unusual physical features even the patient will not be suffering from any medical problems. The persons are usually taller than average as per their height and age also they may be several centimeters taller than their parents and siblings. Few patients were reported to have severe acne, at that time the possibility of the Acne to be related with the chromosomal changes was refused. Now a day few dermatologists are suspecting the relationship of the acne with the karyotype.

Testosterone levels when checked in some cases were found normal, even prenatally. As the hormonal levels are normal so the individuals have normal sexual development. Fertility is not a concern in such individuals; most of the individuals are generally fertile unless some other underlying condition is present. As the condition is not at all related with any of the physical conditions and medical conditions so it is difficult to diagnose the condition. Generally the patients are found only when genetic sampling is done due to some reason.

Some surveys have indicated that the young patients may have a problem in learning. It is also reported that their speech and language skills may be impaired in some patients and some studies suggest that the incidence may be as high as 50% in some particular geographies. It has also been reported that such patients may have a bit lower IQ as compared to their siblings. The difference is very less like 10-15 points on the scale so it is generally impossible for someone to identify or suspect such kind of disorder. Some cases are reported with some kind of behavioral problems but the exact symptoms vary from person to person.

Few cases are also reported with aggressive behavior, some doctors believe that the genotype has strong relationship with the aggressive behavior. Some patients also have developmental delays. The condition is not an inherited condition.

It occurs randomly during one of the phase of the cell division called as metaphase in which there will be nondisjunction in II stage due to which there may be a sperm cell with an extra Y chromosome, the child who gets the chromosome will have an extra Y chromosome in each of his cells.