Steroid treatment has stopped IBS symptoms

There are a few gut problems which are classed as autoimmune - Crohns, diverticulitis and some forms of rheumatic/arthritic things have associated gut problems. Even coeliac disease can cause PMR-type symptoms - and may not be diagnosed until the patient is in their 50s or 60s. It wouldn't respond to pred though - only removal of gluten from the diet will do that. 

Someone has said "Sometimes I think that IBS is used as a catch-all," - IBS should ONLY be diagnosed once all the other potential problems that could cause the symptoms have been eliminated from the inquiry. But far too many doctors decide this is a nervy teen/20s and it is "IBS" and condemn them to a lifetime of discomfort and embarrassment for no good reason. 

Some of the short-lived cases of PMR are reactive to a gut problem - and sorting the gut problem will get rid of the PMR. There was a young man on one of the forums a year or so ago - the doctors were totally flummoxed and we suggested he tried to see one particular rheumatologist who did the detective work and identified a gut problem causing it.

I, on the other hand, have a wheat allergy which started about the same time as the PMR symptoms. No way of knowing which came first - but it is markedly better on the pred and I can eat small amounts of wheat while on pred without problems. It isn't gluten - it is the starch part of the wheat.

If you google it you will find dismissive comments that "IBS isn't autoimmune in origin" - that is old hat and slowly even mainstream medicine is realising that the gut has a lot to do with it and that the concept that the gut is made to leak like a sieve in some cases in response to some trigger is perhaps NOT as "alternative" as has been thought for years.

But it is something to discuss with your doctors at some point.

I’m not sure if the two are related but what I do know is prednisone does mask symptoms of other things going on in our bodies. Glad you are feeling better!