I'm new here - still trying to get a firm diagnosis - but since you mentioned other AI conditions, I'm wondering if you have ever been tested for Celiac Disease? It's much more common than most people realize (1 out of 133 people have it; 97% of them don't know that they have it).

I'm not saying not to pursue MG testing/treatment; just look into the possibility of CD and/or gluten sensitivity (which will not show up on any blood test, but will respond to a GF diet).

It's frustrating to have symptoms, but no "positive" test results....