crissiec,
Did you stumble upon the doctor who finally diagnosed, or was it a specialist you found after the long four years.
In looking at the relationship between immune systems, autoimmune systems and osteoclasts-the cells that resorb bone. I find this interesting, https://pmc.ncbi.nlm.nih.gov/articles/PMC6834200/.
but you may not.
It does seem, from patient reportage, that people with autoimmune systems have more troubled experience with Reclast. There is a Korean study administering steroid before the Reclast infusion. If you do decide to have another injection you might ask for a slower infusion with a greater dilution of the medication. But, at least it appears that the second infusion isn't as difficult as the first.
Explanation from a bone specialist
Up to 30% of patients can experience an acute phase reaction after their initial infusion of zoledronic acid. This APR, which starts usually about 6 hours post-infusion, and can last several days, consists of a fever associated with muscle and joint pains, similar to the symptoms with a bad viral infection such as the flu.
As with the flu, when a category of phagocytic T-cells, called gamma-delta T-cells, encounter the zoledronic acid, they engulf it. When a gamma-delta T-cell undergoes apoptosis, it releases inflammatory cytokines, such as IL-1, IL-6, and TNF-alpha. And these inflammatory cytokines mediate the temperature rise and myalgias.
These T cells aren't the target of zoledronic acid it is the incidental encounter that causes the release of cytokines. When the osteoclast engulfs alendronate or zoledronic bound to the bone surface. the osteoclast undergoes apoptosis (programmed cell death). This explanation from a bone specialist.
Cytokines can trigger the release of more cytokines accelerating the inflammatory reaction resulting in a longer reaction to Reclast. Your doctor seems aware of the possibility type of response. And is on the ready after four days, though the temporary reaction can be a few days longer.
Your situation is quite interesting. I hope Reclast works more comfortably, and successfully.