I'm undiagnosed.. but get IVIG for myasthenic symptoms .. I crashed and ended up inpatient, the labs have been negative, and the repetitive stim was slightly abnormal, but not enough abnormal for diagnosis- however it was performed 10 days after IVIG.. so who knows.. they run the MG/LEMs labs about twice yearly.. all wondering if they will turn positive at some point.. I am Musk negative as well. I haven't had a SFEMG... Thankfully the IVIG keeps me alive for now!