Lupus Foundation of America said...
No one knows what causes lupus. Scientists think that people are born with the genes to develop lupus and that something brings on or "triggers" the disease and symptoms. However, a combination of genetics (heredity), environment, and hormones is involved.
Note
"scientists think" means that there are no official studies to prove or disprove this statement, and basically the answer is "we just don't know".
Some of you may
observe trends of auto-immune diseases in your families or friends families, but until I see a study otherwise, I'm trusting the Lupus Foundation!!