Angell, Can you define the exact kind of pain you're having? Is it only your back? Is it lower, mid, or upper back? A B12 deficiency can cause back pain, too.

Is it sharp, dull, shooting, localized, generalized, in a joint, in a muscle, etc.

When muscles are overused, such as with marathon runners, muscles can cramp up and spasm. There's definitely pain involved with that. They can remain sore for hours or days.

With MG, that cramping or spasming or pain simply happens a lot sooner, due to how weak our muscles already are. But it's a secondary symptom of MG, not a primary one.

Pain isn't a simple issue and can also be caused by a vitamin D deficiency, electrolyte or fluid imbalance, hormone imbalance, etc.

Don't assume that it's caused by MG. Try to write down when it happens, and any other clues you can in an attempt to figure it out. And then, of course, talk to your primary doctor about it.

Annie