Mono is thought to be the trigger for many auto immune issues. I have multiple auto immune issues but never had mono. I was speaking with son's partner the other day who is a Dr and in GP training. It was an interesting discussion as being trained in the UK she was taught a lot about auto immune issues and predicted last year what might be my issue but never told me at the time. She did chat with her mum about it who is an RN.
Auto immune issues run rampant in the female part of my family - Grandmother RA; Mother Thyroid storm in her teens; Me, Thyroid, now APS/SLE; niece SLE. I was healthy in my teens but plagued with headaches but none of the usual childhood stuff. In early twenties and just married 6 months and husband diagnosed with highly aggressive teratoma - survived all the ops but was told he had only 50% chance of lasting 6 months. Obviously the odds were in his favour. In speaking with son's partner I realised it 2 years later I developed the first autoimmune illness being Hashimotos thyroid. After my husbands illness it seemed like a total nothing thing at the time.
Dad died a few years ago but while it was extremely distressing it did seem like it was a natural event and his passing was peaceful as such. We had some awful times with one of our sons that was a parent's worst nightmare, and work stuff that we got through. Then around 2 years ago my mother died and apart from MrP's illness I consider those few weeks to be the most distressful period in my life, I feel haunted by what we did and didnt do. Sure enough, 6 weeks later taken to Hospital and further and more significant autoimmune illnesses found.
Extreme Stress is the trigger for me but it is probably the kind of stress that most people will wilt under.