Which genetic disorder can affect male fertility?

Klinefelter syndrome is the genetic disorder that most notably affects male fertility. This condition arises due to the presence of an extra X chromosome in males, leading to a chromosomal pattern of 47,XXY instead of the typical 46,XY configuration. The additional X chromosome disrupts normal testicular development and function, often resulting in reduced testosterone levels, underdeveloped testes, and impaired sperm production. As a result, many individuals with Klinefelter syndrome may experience infertility or subfertility.

The other disorders listed, while they can influence various aspects of an individual's health, do not primarily impact male fertility the way Klinefelter syndrome does. Turner syndrome occurs in females due to the missing or incomplete second X chromosome, so it does not pertain to male fertility. Down syndrome, characterized by an extra chromosome 21, also affects individuals regardless of sex but is not specifically linked to male infertility. Marfan syndrome, a connective tissue disorder, primarily affects physical characteristics and may have reproductive implications, but it is not directly related to male fertility issues as Klinefelter syndrome is.