Instead of having a normal number of chromosomes which is 46, the Klinefelter patients have a total of 47 chromosomes.
It is also referred to as the XXY or 47, XXY syndrome . Harry Klinefelter, an endocrinologist that belonged to the group that first described the symptoms of the disorder . These chromosomes contain an individual’s DNA and genes.
 Unlike most of the genetic disorders, Klinefelter disease is not hereditary (meaning it is not passed down through families).
It is actually caused by a random error in meiosis (cell division) when the formation of parent reproductive cells occurs.
On the other hand, males possess the X and Y sex chromosomes (XY).
Aside from the determination of the gender based on the sex chromosomes, they also help in the identification of the individual’s sexual characteristics and fertility.
Instead of the normal XY chromosomes, these individuals have and extra X chromosome making them XXY. Males usually have one X and one Y chromosome, i.e. Males with Klinefelter's syndrome have two X chromosomes (47-XXY), in rare cases three (48-XXXY) or four (49-XXXXY) X-chromosomes.
One common treatment is testosterone replacement therapy.
The manifestations exhibit depending on the number of XXY cells that the male has, the age his condition was diagnosed, and the amount of testosterone in the body.
There may be some who will not manifest symptoms at all.
Your doctor may then run two main tests: Chromosome analysis: Also called karyotype analysis, this is a blood test that looks at your chromosomes.
Hormone tests: These check hormone levels in your blood or urine.