I googled MG and pain, to see if I could find anything about pain being associated with it. Found some sort of forum for it, and there's a bunch of people there reporting that they have pain. So apparently you're not alone there on the pain.
http://www.topix.com/forum/health/my...HG01120156A1G2
I bet that MG probably has some pain associated with it. If it affects the muscles, it might be some sort of muscle pain or something. All I know about MG is just what I read about it in the last five minutes. So, this is basically me offering an opinion that I've gotten from five minutes of reading.
I'm still a bit gobsmacked that a doctor told me once (basically swore to me) that multiple sclerosis is not painful. Because that's one of my big issues with the MS. It hurts a lot sometimes. Neurological pain hurts.