Well, this is a complicated topic and I could probably go on about it all day, except for the fact that (a) my fingers are very swollen and painful today because I'm having a rheumatoid arthritis flare, and (b) my eyes are going out on me (blurry vision and double vision from the Lyme disease). So I'll make this fairly brief.
Lyme can mimic MANY other diseases, including lupus, ALS (Lou Gehrig's disease), and MS. Unfortunately, it can also trigger autoimmune diseases, particularly in those who already have the genetic tendency to develop them. So you could have Lyme pretending to be lupus, or you could end up with the real thing! :(
Some people ask me if any of my several autoimmune diseases (lupus, RA, autoimmune hepatitis, Hashimoto's thyroiditis, celiac disease and psoriasis) will go away when I beat Lyme disease. In my case, I think probably not. Some of them could go into remission, but I think I actually HAVE all of those illnesses, because my family is extraordinarily pre-disposed to developing them. We have a long history of AI disease in our family: my dad had RA, two of my aunts died of complications of lupus (kidney failure), my 2nd daughter has Hashimoto's, my 3rd daughter has lupus and Addison's disease, my niece has Grave's disease, and 3 of my 5 grandchildren have celiac disease.
I suspect I would not have developed ALL of those AI diseases if it hadn't been for Lyme, though. In a space of just 2 years I developed 3 AI diseases plus fibromyalgia, and it was just a couple of years after I contracted Lyme.
The key evidence that I actually have lupus is that some of my blood work is positive for the anti-double-stranded DNA autoantibodies, which doesn't usually happen if you just have Lyme. Lyme patients DO frequently have a positive ANA, but not the high level of the anti-DS DNA antibodies that I have.
Of course with everything that I have it's difficult to disentangle the symptoms and decide which symptom is due to what. Most of the time I don't bother....but this morning when I woke up with the swollen painful finger joints and they refused to get better over several hours, I had to email my rheumatologist and ask him whether I should continue to try to cut down on my prednisone given the RA flareup. He said no, keep the dose where it is for now. I first had to figure out whether or not the pain was due to RA, so went on line to check out the symptoms to be sure. For example, RA can show up in the morning but will persist, whereas osteoarthritis can happen in the morning too but usually feels better after 30 minutes or so.
Eventually I hope to get completely off the prednisone, because it is VERY bad to take steroids when you have Lyme. Steroids suppress your immune system, so it can't fight Lyme very effectively. But I have to balance the needs of my Lyme disease with the needs of my AI diseases. Prednisone has undoubtedly saved my liver from destruction by my immune system, which has become very confused and tried to kill several of my organs. It actually did kill my thyroid. But more about that later....
In any case, I wish everyone a very Happy (and hopefully HEALTHY) New Year!!!