I would be interested too. I don't even have a seronegative diagnosis. But I managed to talk my GP into trialling Mestinon over a year ago.

When I started at 30mg, and the effect was VERY positive, I thought I was cured, sort of.

However I have now had to increase that to a much much higher level and although the effect is still positive, it is not keeping up with the progression of the disease (whatever it is that I have) and I am concerned that I shall be hitting the upper limits of Mestinon, even before I get a confirmed diagnosis.