No research has proven Vitamin helps people with MG. However, there's a medicine called Soliris, approved by FDA in Oct 2017, it's a treatment for adults with generalized Myasthenia Gravis (gMG) who are anti-acetylcholine receptor antibody-positive.
Soliris is the first in a new class of drugs to be approved for MG in the U.S.
If you haven't heard or tried Soliris, I'll recommend you discuss with your Dr. about taking this new medicine.