EGFR and rheumatoid arthritis: Importantly, some EGFR ligands of both high and low affinity have been implicated in mediating pain associated with various diseases such as temporomandibular disorder (Martin et al., 2017), vertebral disc herniation and degeneration and radiculopathy (Huang et al., 2017; Kongstorp et al., 2019), rheumatoid arthritis and cancer (Wangzhou et al., 2021) (summarized in Table 1).