“…Patients with reactive arthritis and RA often have a combined etiology of hereditary and microenvironmental factors such as altered microbial flora in the gastrointestinal system (Toivanen, 2003). Bacterial degradation products, their cell walls and DNA, have been identified in synovial fluids from patients with TMD, RA, and reactive arthritis (Klineberg et al, 1998; Toivanen, 2001; Chen et al, 2002; Olsen-Bergem et al, 2016). Multiple experimental studies have demonstrated dysregulated TNFα and malfunctioning TNFR1 and TNFR2 caused by inflammation (Peschon et al, 1998; Kagari et al, 2002; Choi et al, 2010), or neuropathy (Sommer and Kress, 2004), as well as by “double-hit” inflammatory insults that can cause chronic inflammation not only in joints (Hains et al, 2010; Westlund et al, 2012; Traub et al, 2014) but also in other organs (Mariotti et al, 2002; Ilievski and Hirsch, 2010).…”