Vertical flow from upstream triggers through the FM-IgG production layer to the central MAST CELL + MRGPRX2 convergence node — where the Sanchez/Goebel/Dong 2025 finding collapses the H1 and H2 chains into a single chain — and onward through mediator release, satellite-glia activation, and the established symptom outputs. Six numbered red break-points sit on the exact arrows that the candidate clinical-stage interventions interrupt.
Open visualization in its own tabFor two decades, the autoimmune hypothesis (FM driven by circulating IgG) and the mast-cell hypothesis (FM driven by mast-cell activation) were investigated as parallel paths. In May 2025, a preprint from Sanchez, Burgess, Goebel, and Dong showed that FM-patient IgG triggers mast-cell activation via a specific receptor — MRGPRX2 (Mrgprb2 in mouse). Deletion of that receptor, or ablation of the mast cells themselves, abolished the IgG-induced pain phenotype in passive-transfer mice.
The two hypotheses are actually one chain. Substance P (an established FM biomarker for over thirty years) activates the same receptor from another direction. Hereditary α-tryptasemia (TPSAB1 duplication, ~5% of the population) genetically amplifies MRGPRX2 expression and mast-cell density. Estrogen at gluteofemoral adipose tissue provides a third parallel input — explaining the 35–40% comorbidity of fibromyalgia with lipedema.
The clinical consequence: four levels of intervention now have a coherent mechanistic story. Plasma-cell depletion (daratumumab) removes the upstream antibody source. Circulating IgG removal (FcRn blockade, plasmapheresis) clears antibody en route. Receptor antagonism (barzolvolimab, CDX-0159 — already Phase 2/3 for chronic urticaria) blocks the convergence step itself. Mast-cell stabilization (cromolyn at high continuous dose) prevents degranulation downstream. The MRGPRX2-antagonism arm is new as of May 2025 and represents the most direct cure-path test enabled by this unification.