Two things: First of all, when your son's doctor runs blood tests, PLEASE have him add a Celiac screening. If a person has one auto-immune disease, they are more likely to develop more. Celiac Disease is more common than most doctors realize (although the CD groups have done a great job of getting information out there), and 97% of people don't present with "typical" symptoms.

A lot of people with MG say that they have benefitted from a gluten-free diet, even if they don't test positive for CD. It's best to know if he has it, though - a person with CD has to stay on a GF diet for life. It's not that hard these days!

Secondly, it's my understanding that the DOSAGE of Mestinon can affect how one feels. When I was first getting diagnosed (and all of the "standard" tests came back negative), my neuro did a medication trial. If a person doesn't have MG, they won't be able to tolerate even the lowest dosage of Mestinon. (I was diagnosed based on the fact that I could tolerate quite a bit of it at one time!)

Most neuros will start a person out at 30 mg, then work up to 60, 90, 120, etc. If a dosage is too high, the patient will know it within an hour or two, because they will feel absolutely AWFUL.

I couldn't see any difference at 30 or 60 mg; at 90 mg I felt a lot better; at 120 mg, I was on the couch feeling like I was going to die.....

Once you figure out what the tolerance level is, then you start figuring out the timespan that works best. Mestinon changes the rate at which Acetylcholine is absorbed by the body, and the body's absorption of AChE is a very delicate balance.

Most people find that rather than increasing the dosage of Mestinon, they shorten the interval at which they take it if they feel the need to take "more". Increasing the dosage makes them feel bad, and too much Mestinon will affect the AChE levels in the body to the point that a cholinergic crisis might occur.

Fortunately, the effects of Mestinon only last 4-6 hours, so if a person gets too much when figuring out their tolerance level, they will only feel bad for a few hours. It will work itself out of the system pretty quickly.

Good luck with your son's diagnosis - I'm sure it's a relief to have an answer!