Stelara is NOT good for AS. In fact, it failed in phase III trials and the study was terminated early.
Stelara does seem to work for peripheral arthritis but not for spinal (axial) involvement, which includes the SI joints. It's used in psoriatic arthritis but most rheumatologists will tell you that it's not very effective for that either.
To actually have an official diagnosis of Ankylosing Spondylitis, there has to be damage to the SI joints that shows up on x-ray. However, damage takes quite a while to show up - it can take 8-10 years, so it's rare to see it in kids/teens.
If there is no damage visible on x-ray but inflammation is visible on MRI, that means your son has juvenile axial spondyloarthritis (SpA). It has not yet progressed to AS and the goal of treatment is to prevent that progression.
My husband and daughters all have AS. Initially though, my girls were diagnosed with juvenile SpA. My older daughter progressed to AS in 5 years. My younger one took only 3. My husband has pretty severe AS - he also developed severe hip arthritis in his 20s. He has had 5 hip replacements, starting at age 30, fused SI joints, a damaged ankle and some spinal fusion.
Anti-TNFs are the best option for patients with both axial SpA and IBD. Typically Remicade or Humira. You want to treat aggressively, to prevent further damage to his hips and SI joints. My girls have been on anti-TNFs for years and my older daughter did great on them.
My younger one has severe AS - pretty much every joint of hers is involved, from her toes to her jaw. We made the mistake of not treating her aggressively enough when she was younger and only had a few joints involved, and she is paying the price.
She is 22 and it is looking like this year she will need a jaw replacement. She has very stubborn AS - we tried everything: Humira, Remicade, Simponi, Cimzia, Enbrel, Methotrexate, Arava, Imuran, Sulfasalazine and so on. We finally moved on to IL-17 inhibitors - Cosentyx and Taltz - and those have REALLY helped her. However, they can cause a Crohn's flare and aren't meant to be used in AS patients who also have IBD. But because my daughter's AS is SO much worse than her IBD, we chose to risk that.
Her IBD has been mild. Her Crohn's diagnosis was a surprise too - her only symptoms were lower right abdominal pain, some weight loss and occasional constipation. But her Crohn's has responded very well to anti-TNFs, thankfully.
Has anyone heard of re-loading remicade. I have read many messages and haven't read anything about loading doses for the 2nd time. I too understand what you are all going through. Even when he is well, I am always worried that it won't last, and it's causing me anxiety! He was diagnosed at 19 and is currently 20, is pretty thin but has gained some weight since started Remicade. I am glad I found this thread. I think we would all trade places with our kids if we could.
I have heard of reloading with Remicade. Usually it's done when there's been a break in treatment, but it makes sense to do it in your son's case, since there was no Remicade in his body and you're essentially starting from scratch.
There is also high dose Remicade - they can go up to 20 mg/kg every 4 weeks. My younger daughter tried that and it worked for a while. But she doesn't respond well to anti-TNFs in general. My older daughter does. She has had an easier time than her sister, thankfully. She has hip, SI joint, jaw, knee, ankle involvement. But anti-TNFs controlled her arthritis well (mostly) and she has been able to live a pretty normal life.
For juvenile spondyloarthritis, it is not uncommon to get Remicade every 4 weeks. The FDA approved dose for AS is 5 mg/kg every 6 weeks. For Crohn's it's started off at 5 mg/kg every 8 weeks and the dose/frequency is changed if necessary. Both my girls had infusions at every 4-5 weeks when they were on Remicade.