@jck51
Hi @jck51
My Rheumatologist recently told me so directly. At a recent routine appointment with my Rheum, I mentioned that I was glad that my ongoing labs would catch any relapse because I was feeling some of the early symptoms (now recognized in retrospect) of my PMR/GCA and was worried that I might be one of those people who can relapse even while on Tyenne, let alone in tweaking it down or taking a break from it. Doc then said that the CRP & ESR labs don't work as if one was not on Tyenne. (Google Tyenne relapse) I'm most worried about GCA, of course, since it is more serious than PMR (permanent blindness, aneurysms). I wanted to be vigilant about any symptoms creeping in without being a "hypochondriac" which I've never been (kind of the opposite to a fault). She said that when a person is on Tyenne treatments, that the Tyenne suppresses reliable results in CRP and ESR labs--can't remember her exact words, but something like "they don't work". Why I didn't ask her the question, "Then why do they still do these labs?" Next appointment will question. I'm assuming they might still yield some useful idea? July 2024 my CRP was 159! Diagnosed with PMR/CGA, classic symptoms. Sept 2024 CRP < 1.0 after 60mg Prednisone started end of July 2024. Prednisone slowly tapered to 0 in July 2025. Tyenne was started Sept. 2024. Nov 2025 CRP< 3.0 onward to now. Monthly Tyenne continues. They didn't do my ESR until October 2024 after I was on high dose Pred, so that lab was not indicative of PMR/GCA due to daily hd steroid treatment.
Like you, I experience muscle weakness (so unlike my prior, undiagnosed self!) in my thighs, but not really pain. My hips have some pain, though & also my elbows. And pain & weakness in my shoulder girdle. I am aware of these symptoms as I try to ignore them and do everything (albeit sometimes moderated) I used to and want to do. I have a physical job (caregiver for elderly). All the lifting, carrying, cooking, chopping, slicing, washing, weeding, housework..... I'm sure it adds to my aches, whether muscle or joint, but I think the key is to keep active and be aware of limits, moderating personal overdo tendencies. I notice in walking back to my car after work that my legs feel heavy and weak. But I just keep going, unlike when I crashed & was diagnosed and could barely walk before wanting to just crawl on all 4s from my bed to the bathroom (before Dx). SO MANY abnormals labs then!!!

I may never go back to how I felt pre-diagnosis (likely), but I am grateful that I can take long, hilly walks (6 miles) and even though I "feel" it, especially at first, I seem to feel better the longer I walk & exert myself (hills) up to a reasonable distance for someone with PMR... So, while legs start out feeling weak, they still can do what I want them to do and end up feeling better after I'm finished. I think we feel it most after being sedentary (and, say, go up a set of stairs?).

Ask your rheumatologist what s/he knows about the usefulness of CRP & other labs while on Tyenne and report back (-: . I will too.

Aside: I had the classic symptoms (most) of GCA, along with PMR, but since they scheduled my temporal artery biopsy 11 days after I had started 60mg Prednisone (urgent to start asap), even knowing that Prednisone for this long could make the biopsy a false negative, it did come back negative, but they knew that I had GCA from the frightening symptoms. THAT was a biopsy I wish I had known to say "NO" to since they were going to treat me anyway and I think they should have either found a way to schedule it at the outset (fat chance!) or not do it at all--waste of time/skill/talent when known to come back false negative.

In all the testing & scanning, though, they did find a small ACA brain aneurysm that they are monitoring, thankfully no growth in 1 year. GCA can cause anuerysms. However, no way to know when this aneurysm came on.

@jck51 Please understand that members of Mayo Clinic Connect are not medically trained so we often don't really understand whys. We are all patients of a Dx that is confounding even to the doctors treating us. PMR/GCA/vasculitis are all uncommon to rare medical problems with limited knowledge professionals available to treat us.
I can not get a consistent answer when I ask just two rheumatologist. I have a treating doctor where I live and I have a 2nd opinion Rheumy who works with a different teaching hospital in a different state. Some days I'm not sure they would agree on sunrise in the East vs. West.
As far your question on Inflammation markers while on an IL-6 biologic. I asked my AI tool and it dumbed it down so I could understand. They are indeed not reliable when on Actemra/Tyenne. Possibly you use an AI tool and can query it. I have learned to change the question I ask if my tool doesn't answer my question on the first try. You can also try doing a simple internet Search -ask Dr Google.