Seronegative myasthenia gravis is more common than many doctors seem to realize. The article below says that different studies have shown that between 7 and 34% of MG patients are seronegative. Not only that, but the earlier in the disease, the more likely that the patient's blood tests negative.

"Seronegative" is a misnomer, though. It just means that the blood tests can't find the antibodies. The antibodies are there, because when the immunoglobulin from seronegative patients is injected into animals, the animals show abnormal neuromuscular transmission.

I'm posting this here to tell readers who are seronegative and undiagnosed not to let their neurologists rule out MG too quickly.

http://www.neurology.org/content/48/Suppl_5/40S.short

Abby