Chaos, I believe that trauma/stress can bring things to the surface that might not ordinarily appear.

When my severe visual exacerbation happened (the one that got me the MS diagnosis) in 2005 I had been through several traumatic events in the months prior. My Dad passed away in January, my Mom passed away in March and in April I was deathly ill with two back to back bouts of bronchitis. I don't think I was that sick even when I had Mono. It took several months to recover. Then in October I had the visual exacerbation and it was downhill (MS-wise) from there.