There are statistics that show that lupus favors asian, negro, and American Indians more than other groups. It also favors women 9 or 10 to 1. No one really knows why since they are still trying to determine what the actual disease mechanism is.
I am a man and my ancestory is Scotch/English. If you go back almost a 1000 years ago I am probably descended from Vikings so I don't fit the stats very well at all. I also got it later in life (almost 63). Don't seem to fit the patterns at all. I have a younger sister who has a mild case of lupus but no other family members in known history have had an autoimmune disease of any kind.
The thinking is that all of us have a set of genes that predisposes us to some kind of a trigger or triggers in our lives. Auto immune diseases (not a particular one) have been shown to run in families. In other words, one member can have lupus, another RA and another something else. Not a true genetic disease and not all members will have exactly the same genes or the same triggers.
There is also some evicence that initial triggers might not be quite enough to display symptoms and it might be a long time between those events and when symptoms are displayed. That is why it can be difficult to determine the actual triggers.
There has also been evidence that in the last 3 decades or so AI diseases (except RA) are on the increase. Some of the thinking is that we have been exposed to more environmental pollutants and food additives and even viruses from far away places. Actually, most flu viruses are thought to originate in China from traditional farms where people, hogs, and poutry all live together. No one is really sure on why AI diseases are on the increase....maybe it is just that they are finally being diagnosed and in some cases just recognized.
In my case of MCTD (lupus, scleroderma and polymyositis) there were no obvious triggers. No cancer, virus, stress, etc. However, I believe that it had been lurking for at least 15 years and dated to a period of time when I had 2 bad viruses and lots of stress. However, except for mild anemia and low platelets I remained asymptomatic until 2005. Nobody has been able to answer my questions.
Most likely there is nothing that we have done that would have prevented lupus. There are many who have myositis (inflammatory muscle diseases like polymyositis) who believe their trigger was a drug....a statin or cholesterol lowering one. Researchers know that they cause muscle problems but not if they actually cause myositis.
Gene researchers are just now beginning to tackle the puzzle of genes and auto immune diseases. Hopefully, in a few years there will be some answers and some hope for new treatments. Lupus and RA will probably be the first as more money is being pumped into research. Myositis diseases are much rarer and are the poor step children to lupus.
I believe that for the vast majority of us the acutal cause is an inherited set of genes and the triggers will never be known. Some people believe that one thing or another was the cause or trigger but there is usually no hard scientific proof. Until researchers identify the genes and determine the cellular chemistry that causes our disease all of us are just guessing.
Hang in there and deal with it as best you can and define a new normal for your life. I have gone from near death, being a quadriplegic (lost 40 lbs of muscle in a week), and being unable to swallow anything just 2 years ago to leading a fairly normal life. Not the same as before but good. I still hope to recover and return to "normal" but age is against me now. Despite that I do everything I can to recover and also enjoy life along the way.
Good luck.
Bill