It's a combination of a possible genetic disorder resulting in a metabolic dysfunction where heavy metals are not detoxified, and the introduction of thimerosal into the bloodstream. The MMR vaccine is thought to be the trigger in many cases for this metabolic disorder.
I'm going to be very wary of all of this. Best thing to do, folks, is to get your immune systems in good condition by eating your fruits and veggies! LOTS of them. Raw, if possible.
Make sure you wash them VERY well, as there are many neurotoxic pesticides on them these days.