I don't know how much help I am going to be with your concern, but wanted to give you some reply seeing how no one else has.
I also have Myasthenia Gravis, not in remission and I have Generalized Myasthenia Gravis. I am not stabile yet and it pretty much effects all systems but I am still functioning, so thats good.
I recently retired from the military and was denied life insurance from a civilian company because of elevated liver enzymes too.
AST 43/GGT 212/ALT 92 - after some internet research it appears there are other people out there like us. I haven't been able to see my Neurologist yet, but I do next week. As soon as I see her, I will let you know what the cause is. Because I feel naked with out insurance.
Plus, when I had my thymectomy in August of this year (2011) the surgeon checked out my liver and said that it looked very healthy. Whats the point of living a healthy lifestyle if you are going to get some weird liver disease, right? Just kidding!