Pleiotropy

Means the production by a single thing of two or more apparently unrelated effects.
In gene biology the production by a single gene of two or more apparently unrelated effects. 
Pleiotropy (from Greek πλείων pleion, "more", and τρόπος tropos, "way") occurs when one gene influences two or more seemingly unrelated phenotypic traits.
A mutation in one single gene cause a disease with a wide range of symptoms? This process is referred to as pleiotropy. A pleiotropic gene is a single gene that controls more than one trait.