Do you eat a lot of sodium? Even so, swelling of the feet implies some sort of circulatory issue, either with the blood or lymph system (or heart). Or it might be some form of an inflammatory disease, since it was bilateral. Did you try taking an anti-inflammatory such as Advil?

Have you ever had the RA test for arthritis? Any other inflammatory tests?

It's not a sign of MG at all!

I would consult with your primary doctor about it.

Annie