Dr Henry Klinefelter who the syndrome is named after, after he discovered a group of symptoms found in males who had an extra X chromosome. Not every male has similar characteristics of those described by Dr Henry Klinefelter so some males affected are referred to as XXY males. Medics believe that it is one of the most common syndromes with one in every 500 to 1000 males having an extra X chromosome but not having any actual signs or symptoms. Different variants of KS are less common resulting in less than 1 in 50,000 males or even lower in newborns. As mentioned before often the condition can go undiagnosed as sign and symptoms can be mild or not noticed atall and some may not experience any. Symptoms of KS may be overlooked or diagnosed as something different as they can have similar characteristics to other disorders.
Klinefelter’s syndrome (KS) is not an inherited condition so it is not passed on by either parent. It is thought to randomly occur during meiosis process. Meiosis is a specific type of cell division that occurs in the egg or sperms cells in a male or female. Klinefelter’s syndrome takes place because there was a malfunction when the cells were dividing referred to as nondisjunction and an egg or sperm may contain an extra chromosomes. Human Beings have 46 chromosomes totalling 23 pairs of chromosomes, it is when the chromosomes fail to seperate correctly during cell division that causes an extra chromosome to be present. If an egg or a sperm contains an extra chromosome when they meet an egg or sperm that contains the right amount of chromosomes and they fertilise the overall product being the foetus will contain an extra chromosome. When an extra copy of the X chromosome is present this is known as a sex chromosome trisomy.
Naturally there should only be two chromosomes in each body cell i.e. XY or XX, one inherited from each parent, when a third is present it results in a trisomy. Full trisomy is when cells are affected with the entire chromosomes and partial trisomy is when only a part of the extra chromosome has been copied. In some affected males not all the cells contain an extra chromosome, it can be the case where only some cells are affected this is referred to as mosaic KS and the effects are milder. However in rare cases there can be multiplies of chromosomes copied in one cell which can make the effects more sever. Mosaic KS is not inherited and has occurred at the random stage during cell division during foetal development.