If someone doesn't have lupus in his past life.why is it suddenly comes on at age 36?is it a switch in the body turn on coincidently?is it environment

Perhaps: Autoimmune diseases such as lupus are considered conditions from impairment in immune regulation (which tends to worsen as we age). Sun exposure has been known to trigger a lupus exacerbation but is not a cause. Perhaps environmental factors may have something to do with it but we have little knowledge of that. Increased abdominal fat many add to the inflammation. Female hormone may play a role.