Each insurance plan has their own policy about coverage for asymmetry. Your best bet is to start with getting letters of support from your primary and or gyn physician stating the issues you deal with because of your asymmetry (i.e. back/ neck/ breast pain, rashes, grooving of the shoulder(s), inability to fit a bra properly, discomfort with certain activites etc).
I would recommend that you write a letter also telling the insurance company the issues you deal with because of your asymmetry and get additional letters from any practicioners who have treated you (i.e. massage therapist, chiropractor, physical therapist, etc).
Take these letters of support with you to your initial appoitment with your plastic surgeon, and he will submit them along with the documentation he gathers from your visit to the insurance company for approval. He should be able to tell you if you may qualify for a breast reduction with your insurance's requirements (# of grams per breast to be removed is based on your height and weight for insurance approval along with your symptoms and treatments tried before).
Hopefully this information is helpful, best of luck!
