I have a genetic defect that effects my metabolic system which, in turn, causes thinning of my brain's myelin. When it got past a threshold level, I got virtually all of the MS symptoms with a month or two. I am diagnosed with an adult leukodystrophy (unknown type). My brother has it too. My older sister has more damage but no symptoms. She's of the fat myelin, we say, and ought to diet (a little black humor)