Superficially, this contrasts with Chen et al.'s recent pre-pub, which suggests that IgG from patients with PACS—with high neuronal or leucocyte activation proteins titres but not skeletal muscle proteins—are proalgesic upon passive transfer.12 The absence of symptom transfer in our cohort indicates that the pooled PACS-IgG was not pathologically autoreactive (similar to Chen et al.'s negative skeletal muscle protein group) or that an unknown adjuvant, as in CRPS,24 is required. Here, PROS1 is linked to complex regional pain syndrome.