Ugh. There had to have been some “event” as my husband would call it, but you’ll probably never know. A girlfriend of mine had her daughter when she was 4 and her best friend both get sick and both had seizures. Neither had very high fevers with the illness. The other girl just had the one. My girlfriend’s daughter seemed to have a couple more, they suspected that was what was happening. She went through several tests and in the end hasn’t had a problem since. She is 12 now. It was weird. Having a febrile seizure isn’t that. Weird, but they didn’t have high fevers and it usually happens in infants when related to fever.
This same girlfriend and I were diagnosed with thyroid problems within a few weeks of each other and I had just visited her 2 months before. I had had my thyroid tested by happenstance a month before visiting along with other regular tests, and it was perfectly normal.