The appearance of sacroiliitis [inflammation of the sacroiliac joint] is really the hallmark sign of Anhylosing Spondylitis. Xray evidence does not appear until much damage and fusion begins therefore a MRI is the best way to examine the SI joint for inflammation. HLA B27 is one of the tests that they sometimes use to aid in making the diagnosis of AS but it is really not that useful. Many people with AS are HLA B27 positive but you can also have AS and be negative. Aslo, many people carry the HLA B27 but do NOT have AS. I believe HLA B27 occurs in about
8% of people of European descent.
Now, you can also have significant spinal involvement, large joint involvement, and enthesitis [tendon insertion point problems] without having AS. This is called spondyloarthropathy associated with Crohn's disease. This often acts independent of Crohn's flares. In fact, my original diagnosis was spondyloarthropathy [SpA] with enthesitis. My gut was in remission and the joints flared like crazy. In fact this is now a worse problem than the CD. Eventually the right SI joint got into the act and became inflamed, thus the move to calling it AS. My rheumy says that SpA and AS are essentially the same - the treatments for them are the same.
I have to unload my groceries, but I'll try to get back here later and offer up some suggestions of things to ask her
Moderator Crohn's Disease Forum
CD, Ankylosing Spondylitis, lupus, small fiber peripheral neuropathy, avascular necrosis, peripheral artery disease, degenerative disc disease, and a host of other medical problems.