I had unexplained extreme fatigue for a couple of years, my GP couldn't figure it out until one day she decided to run an ANA. She then told me she thought it might be Lupus, and sent me off to the rheumatologist. He took one look at me, at my lab tests, and started treating me immediately.
Others will more mysterious symptoms may take a while to get a firm diagnosis. Sometimes Drs are a bit hesitant to diagnose until they are absolutely positive. I've found that starting treatment is sometimes more important than getting a diagnosis (unless you need the dx for insurance or disability) -- with a disease that presents in so many different ways, often they need to see how it responds to different medications to actually determine if it's Lupus vs. other similar diseases.
Lynnwood, Lupus & Sjogren's Moderator, Dx: 2000DIAGNOSING LUPUS & HW's LUPUS 101
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