At the time I was diagnosed, I had a sudden onslaught of symptoms that led to a pretty quick diagnosis. But in retrospect, there were a number of symptoms that had been mild in the preceeding 10+ years that were also likely lupus symptoms (complete lack of tear production/severe dry eye, pleuritis not related to a coughing spell, slightly aching knees & elbows/wrists, red facial rash that had been misdiagnosed as rosacea, a sun sensitive rash on my forearms).
But at the time I got really sick... it did seem to come on quite suddenly and quite severely too. Had a long term fever, badly aching joints, swollen toe, incredible fatigue... truly like a bad case of the true flu that lasted for weeks.