My celiac was diagnosed soon after symptoms, so no long-term exposure to high levels of antibodies or visible damage on ileoscopy. I have the HLA-DQ8 0302 gene. My IgA, IgG, and IgM antibodies are all in normal range; bloodwork doesn't check for other antibodies. I have low C and D so take vitamins. I have a few symptoms of but no diagnosis of hypoparathyroidism, mainly bone spurs, muscle cramps, also an iregular heartbeat if I get glutened. You mentioned chemo and steroids, which aren't generally given for MGUS or celiac; steroids are sometimes given for colitis (mine is controlled by no NSAIDs [aspirin causes flares]). I did an elimination diet to see if I was sensitive to other foods. If you have a colonoscopy, ask them to also check for microscopic colitis (happens with celiac and the colon looks normal). The hardest thing about illnesses is the social isolation. This hit me soon after celiac diagnosis with comments (not being invited to dinners, fad diet...), and difficulties finding places to safely travel and eat. There are celiac disease support clubs that help with the isolation. I volunteer to counter the isolation. It is important to take care of yourself physically and emotionally. Autoimmune diseases don't seem to increase our risk of getting infected with nasty things like covid (we're more careful?) but could impact the severity. I got covid and glutened on a March bike tour, so a double cytokine storm ( vaxxed and boosted, but still felt like hell). I'm 69 and my diseases haven't limited me but living with them requires good swear words.