Originally Posted by mrsD

GBS is not likely to cause swollen joints.

Rheumatoid arthritis does not always have good testing success.
I had it done twice over the years, and my doctor said false negatives are quite common. As the disorder progresses, the
immune factors may become evident later.

This sounds like an autoimmune disorder. Arthritis like this can come from Lyme disease and also some vaccines.

Strep can attack joints too. So I am thinking the doctors will explore these options.