Aberrations

A "negative" mutation. They are genetic abnormalities that impair you in some way, or that may give you some kind of advantage but at the cost of losing your ability to properly function as a "normal" human being. This may happen due to physical or social impairments of some kind.
For example, you may develop something so damn far fetched that you lose resemblance to a human, hindering social interaction and integration to different degrees.
As a specific type of mutation, Aberrations can also be expressed, repressed or supressed, in accordance to all the rules of the Mutation System.