Any form of assault/ trauma that can rev up or stress the immune system can apparently trigger lupus in the genetically predisposed or cause a flare up. It might be an accident, pregnancy and childbirth, infections, surgery, extreme dieting, environmental factors and toxic exposures, some medications, lack of sleep and very poor life style habits,even a too fatty diet, you name it, it's possible. There might be several factors in any one case. I have heard it compared with being dealt a particular hand of cards.
Very often people realise on looking back that they have had lupus symptoms all along.
Cheers
Clare