Genetic Factors

Examples include the following: 

• Cystic fibrosis patients often have missing or obstructed vas deferens (the tubes that carry sperm) and hence a low sperm count; 

• Klinefelter syndrome patients carry two X and one Y chromosomes (the norm is one X and one Y), which leads to the destruction of the lining of the seminiferous tubules in the testicles during puberty, although most other male physical attributes are unimpaired;

• Kartagener syndrome, a rare disorder that is associated with a reversed position of the major organs, also includes immotile cilia (hair-like cells in lungs and sinuses that have a structure similar to the tails of sperm). Germ cells may also be affected by this condition.