I am so glad you got the rheumy consult. Whether or not he has your DH's blood type, I really don't think is any consequence. I have done a lot of research on JRA because my DD has palindromic rheumatism. Which is JRA that comes and goes. It isn't as severe as JRA.
But, YES, having a direct relative with lupus gives him a bigger chance of having JRA. Sorry. I don't want to be the bearer of bad news. I found out that because I have psoriasis, all my children could be susceptible to an autoimmune disease. I didn't even know that. I also did not know that since it has been 10 yrs and I haven't developed RA, I am lucky, and probably won't. But, they go hand in hand.
We've had a long road trying to figure out what was going on with my DD. She will flare up for about 24-72 hrs from her back to both legs. She was also a tomboy and very active. I will share real quick what happened with her, as it is very unusual. Maybe there is something in your son's activities that will give you a clue.
My DD got bit by a dog Aug 8, 08, on her birthday, in her face. They stitched her, gave her a tetanus shot, but didn't put her on ABx. Since my baby was in the hospital, and my friend had her treated and was hysterical, neither of us thought about the ABx as a prophylactic. So, FF to mid Jan. She starts with a hip limp, which went to all of the joints on her right side and both legs were in pain. We went back and they tested her for strep. She was strep pos twice, and took 2 ABx, but NONE of my other 6 children got it from her, and they share a LOT. So, the dr and I believe she did get strep from the dog bite, and it went untreated because we just never knew.
So, as time went on, and it wasn't getting better, but worse, she was tested for Lyme, as was suggested. Well, the dr said he would test for ALL tick borne illnesses, although this was April and she hasn't been bitten since 2yo, and her back was being affected at this point. My theory was that she got Lyme from the dog bite. I asked if she could have Rocky Mountain Fever from the dog bite, and he laughed and said after this many months, if she had RMSF, we wouldn't be talking about it. (It is a very severe illness.)
Lo and behold, I find out 3 wks later that she tested pos for RMSF after they wanted to do the test again, per protocol. That came out pos too, but no one believed she had it as she was never hospitalized for it. But, she had a rash on her face TWICE that resembled this disease rash, not far from the bite. I even took a pic the 2nd time. It stayed for 2-3 days each.
So, I finally got the other ped to give her the correct ABx for RMSF. And, she gets BETTER!!!!!! After MONTHS of pain and having this come back over and over, she seems to be getting better. She does still flare, and she may for the rest of her life, but PR and other JRA can be activated by viruses and bacteria, which she has had a lot of besides from the dog bite, from my med fragile son catching everything under the sun and the other kids being sicker this year than ever before.
We're hoping that my DD's issues don't turn JRA, as it still can. She flares once every 3-4 wks, and I can't be sure that she didn't flare this last time from the stress of having 2 siblings in the hospital at the same time. But, it was about her time too.
Ibuprofen is good. Aleve can be better. My DD is allergic to Aleve. I hope for a quick cure or a quick diagnosis for your son. PM me anytime. I am not an expert, but I do know of some links if it is JRA, and the frustration of how long it can take to figure things out. My DD is still officially undiagnosed. But, we are getting a 2nd opinion at another rheumy's on Oct 7th. The first rheumy tried to say she was making it up or having "sympathy pains" because her brother is med fragile. NOT this child!! So, hopefully we can get some real answers there. Kymberli