The normal karyotype of a male contains 22 pairs of autosomes and 1 pair of sex chromosomes (XY), so his karyotype is 46, XY. However, a man suffering from Klinefelter's syndrome will have an altered karyotype, as these men have an extra X chromosome. Thus, the karyotype of a male with Klinefelter syndrome will be 47, XXY.
Klinefelter syndrome is a genetic disorder that causes a lower concentration of testosterone, which prevents the production of sperm. Therefore, this syndrome is considered a cause of male infertility.