49 XXXXY syndrome

Overview
49 XXXXY Syndrome is an extremely rare sex chromosomal abnormality; as its name indicates, a person with the syndrome has one Y chromosome and four X chromosomes. As is common with aneuploidy disorders, 49 XXXXY syndrome is often accompanied by mental retardation.

It is genetic, but not hereditary. This means that while the genes of the parents cause the syndrome, there is a small chance of more than one child having the syndrome. The mental effects of 49 XXXXY Syndrome vary, much like Down syndrome. Males with the syndrome tend to have impaired speech and behavioral problems. Those with 49 XXXXY Syndrome tend to exhibit infantile secondary sex characteristics and have some skeletal anomalies.

It can be considered a variant of Klinefelter syndrome.