CLOCK and rheumatoid arthritis: In addition to the genetic disruption of clock-controlled KLFs, a variety of other systemic perturbations—such as high fat and ketogenic diets, arrhythmic feeding, caloric restriction, alcohol consumption, lung cancer, and rheumatoid arthritis—may result in de novo circadian oscillations in the liver (Eckel-Mahan et al., 2013; Gaucher et al., 2019; Greenwell et al., 2019; Makwana et al., 2019; Masri et al., 2016; Poolman et al., 2019; Tognini et al., 2017).