What you are failing to understand in the case of that person is the effect of biotoxins, from both mold and lyme/coinfections, and the resulting neuro inflammation. For some people, its actually an effect of the innate immune system. Seizures are a common symptom of that.
No, that is not a part of the methylation cycle. But, many inflammatory and neuro diseases at their heart are caused by poor methyl cycle function, look at autism or Alzheimers as an example.