Plaquenil hasn't been known to cause MG, only exacerbate it in some MGers.

http://www.ncbi.nlm.nih.gov/pubmed/22160434

http://www.ncbi.nlm.nih.gov/pubmed/23588942

http://www.ncbi.nlm.nih.gov/pubmed/24254965

Neurontin, however, has been shown to have a correlation between not only exacerbation, but initiation of MG.

Since you have had a clot, I don't think starting/stopping Plaquenil is a good idea. Trust your rheumatologist. A MG diagnosis can still be made while on that drug! But also trust your instincts and keep your doctors informed of any changes!

It could just be a coincidence between Plaquenil and the hotter weather! Heat makes MG so much worse. There's a reason for that. Heat increases the enzyme called Acetylcholinesterase (AChE). When Acetylcholine (ACh), which is a neurotransmitter, is done with its job of making your muscles strong, AChE comes in and cleans up any excess ACh. It's the body's version of a checks and balance system.

So, when the body gets hotter, no matter if the cause is infection, exercise, weather, or whatever else, the enzyme increases and the body has less acetylcholine for the muscles to use! MGers already start out with less of the "muscle gas" getting to the muscles, so it makes us so much weaker.

Before I was diagnosed with MG, I had all sorts of twitching and cramping of muscles. When I have had exacerbations or a crisis, my muscles can cramp up or go into spasm. During my crisis, my left hand actually contorted up a bit after holding something for a minute!

Our muscles can get weak on a spectrum from mild to severe. When they can't hold a contraction well, whether that's from continuous use or overuse, that's when they "act up" and twitch, cramp, or spasm.

I know that people tend to think ALS, but ALS is not fatigable. It's a progressive weakness (unfortunately).

Has anyone checked your electrolytes? A fluctuation in them can cause muscle twitching as well.

The MTHFR mutation seems to be more common in those with AIs. APS is more common, too. I'm glad you're taking methylcobalamin! I hope you do it a couple of times per day. The body needs a continuous source of it. Insurance should really pay for that!

Do you get a rash while in the sun?

I know more than most about lupus, because I volunteered to the local foundation for 10 years (design, writing). It can come on slowly, as I'm sure you already know. It sounds as if you have a good rheumy and that's half the battle with lupus. Stupid little disease!

Did she do a urinalysis to check for protein, too?

I hope you get some answers soon. Stay the heck out of the heat!

Annie