SCN11A and familial episodic pain syndrome with predominantly lower limb involvement: Nav1.9 mutations identified in patients with adult-onset painful neuropathy or early-onset familial episodic pain type 3 (FEPS3) render small DRG neurons hyperexcitable, underlying enhanced pain as experienced by the patients (Zhang et al., 2013; Huang et al., 2014; Han et al., 2015, 2017; Leipold et al., 2015; Okuda et al., 2016).