Klinefelter Syndrome is a surprisingly common genetic defect, with about 1.5 of 1000 births involved. This makes it the most common sex chromosome abnormality in males. While it is called Klinefelter when boys have it, a similar condition in girls called Triple-X syndrome.
In fact it has been suggested that George Washington, first President of the United States, may have had it. This is in part due to his lanky physique, lack of facial hair and no known offspring, despite healthy marital relationships.
The syndrome is basically the result of an extra X chromosome, resulting in an XXY format in boys and an XXX format in girls. Sometimes there is more than one extra X, but this is very rare.
Children with the syndrome are often born smaller than usual, but usually grow faster, especially in their limbs. As the child matures, the growth rate slows to a more normal rate.
&They are frequently sterile, and boys sometimes have one or both testicles undescended. Some tend toward obesity, but the majority are tall and gangly. Height is usually not excessive, no more than 1″-4″ above normal.
Some children display behavioral problems or learning disabilities, but this is not always the case. Other symptoms include boyish voice, lack of facial hair and enlarged breasts, but not all symptoms are displayed in all cases.
Many people with Klinefelter / XXX display few or no outward symptoms, and lead relatively normal and successful lives, as is obviously suggested by the case of President Washington.
There is no treatment for the condition, although surgery may be prescribed for physical symptoms. Professional counseling is advised in dealing with sterility and other manifestations of the condition.