Xembify Reaction - concerned about continuing
Hey y'all. I started Xembify on 4/1/2026, and I have had two infusions total. First one, I had a gnarly headache and bad fatigue for a good few days as well as my bone pain and overall aches and pains ramping up. Second one, seemed okay until the next day, I was completely wiped out, and the side effects from the first infusion also kicked in.
So this is where things start to change. Two days later, I woke up with a tomato red arm , in the infusion site, that was hot to the touch. I assumed just a delayed reaction. But the next day, I woke up with a rash in the infusion site. Small little bumps, similar looking to cholinergic hives. The next day, I noticed the previous infusion site, from two weeks prior, was doing the same thing. And then, they started to spread. Mostly localized to my arms, where the infusions were administered, but rapidly spread. My fatigue off the charts. Brain fog, so bad. Off and on headaches, chills and upset stomach. Some of the worst bone pain I have ever experienced.
I spoke to Grifoils, the manufacturer of Xembify, and they advised I stop the medication, and informed me this was more indicative of a systemic reaction, and could potentially get worse the next time I infuse. However, my immunologist wants me to continue. He did say the reaction was concerning, but he wants me to continue! I don't feel comfortable with this at all. He is adding 4mg dexamethasone to my pre-med regimen (which, the pharmacy is taking their sweet time filling this) and he did say he also is concerned about it getting worse and that it's a systemic reaction as well.
I don't know what to do. I'm very scared to be honest, and I don't think it's safe for me to continue. I'm not sure as to what the issue is either or how to narrow it down. I have multiple medical conditions, including SAD (which is what the SCIG was prescribed for), mast cell involvement (my diagnosis for the last few years is MCAS, but immunology and specialized gastroenterologist suspect that I actually have either indolent systemic mastocytosis or monoclonal mast cell activation syndrome), small fiber neuropathy, ehlers danlos, primary adrenal insufficiency, and dysautonomia. I am on a daily cocktail of all kinds of mast cell stabilizers and I am steroid dependent due to the adrenal insufficiency. I am not sure what is causing the reaction, if it's reacting to excipients in the medication, the medication itself, or who knows. I did ask before I started infusions to be tested for anti IGA antibodies but I was told that wasn't necessary.
I pre med with benadryl. I have been on a sick day dose of steroids and extra antihistamines for the last week and it barely has made a dent in this reaction. I'm worried about this getting worse, and not only triggering a worse reaction, but the reaction triggering an adrenal crisis. This is so stressful.