I'm not sure I have the following right, so please take with a grain of salt, and correct me if I'm confused...

Seronegative MG doesn't mean there aren't antibodies; it just means that the doctors and lab technicians haven't found them.

I can think of two reason why a person with MG would test negative for the antibodies: because they're there, but not in the blood at the time of the test; or because they're there, but they're not the kind that the tests are looking for.

The two best known antibodies that cause MG are AChR and MuSK, but there are several others that we know about. It seems likely to me that there are many other kinds that we don't know about yet.

So "seronegative" doesn't describe the MG, really, just like a UFO isn't "unidentified" in itself. It's something, all right. We just don't know what. The title just expresses the testers' ignorance. It doesn't describe the disease itself. "Seronegative" is a misnomer. It should be called sero-unidentified MG or something.

I have seronegative MG. I was tested three times for the AChR and once for MuSK (and once for LEMS, too). I don't respond to Mestinon, and my symptoms are atypical (almost no eye involvement). My best guess is that I have an antibody that hasn't been discovered yet (or one of the exotic ones that aren't normally tested for). But who knows. I think I am responding to the immunosuppressant drug I'm on (Imuran), so that's an indication that the problem is an antibody.

Abby