Because Lupus is a systemic disease, it can affect every part of the body; the skin, the muscles, the tissues, the organs, the blood. As such, there are many ways that the disease can become severe and/or even fatal. However, statistics state that death, as a result of lupus, comes from infection (we don't fight it well and the immunosuppressive drugs we take don't help), kidney disease (half of us have kidney involvement), and cardiovascular events (we have premature atherosclerosis as a result of inflammation, pericarditis due to inflammation, and some have clotting disorders).
However, if a lupus patient flares and seeks medical attention promptly, the flare is not that likely to lead to death, but keep in mind that lupus is a very unpredictable disease and, as such, we must be diligent in taking steps to avoid flare-ups.
Yes, you should ask direct and frank questions of your doctor. Insist that they respect your fears and your inquisitiveness and that they answer you. However, remember that we are here to help you as much as we can.
Peace and Blessings
Look For The Good and Praise It!