Thus, even when the last reported episode of rhabdomyolysis was on average 6 weeks prior to biopsy, when serum CK activities (155–963 U/l) were relatively normal and when degeneration, macrophages, and inflammatory cells were inapparent in histologic sections, the muscle of RER-susceptible horses had molecular signatures of NF-κB activation, inflammation, and cellular stress. Here, NFKB1 is linked to rhabdomyolysis.