The world was peppered with a mix of dirty nuclear weapons and too many biological weapons to count. This has caused a fair amount of genetic damage, and the gene-altering effects of magic’s return haven’t helped much.
Many humans, and a few metahumans born in these days are mutants, while others develop scars or defects as they are exposed to particularly virulent toxins or bio-agents. The number of mutations falls in enclaves, and other fairly clean places, and is worst in the most contaminated part of the Wastelands.
Still, it’s difficult to get an exact count on how many mutants are out there, due in no small part to the fact that many mutations can be concealed by regular clothing, or are strictly internal.
Mutations do not grant superpowers. They are deformities, or physical disabilities, and is considered impolite to bring them up in most communities. In some of the more backward communities, mutants are persecuted, with many of the same prejudices and methods used against meta-humans.
If you want to play a mutant, that’s fine with us! Figure out whether or not your character’s mutation is visible. If it is, then use makeup or props to represent it, and to try to make it look good. It really adds to the ambiance.
PC’s and NPC’s cannot have a mutation that duplicates the racial makeup and costuming of another playable race. No horns unless the character is a troll, no pointed ears unless the character is an elf.
Playing a mutant has no rules benefits or drawbacks. It’s strictly a social roleplaying focus.