Further confirming the role of inflammation in fibromyalgia pathogenesis and associated pain, Tsilioni et al. found increased SP and haemokinetic-1 (HK-1), structurally related to SP, as well as increased levels of IL-6 and TNF-α in the serum of fibromyalgia patients, suggesting mast cells as the main mediators of inflammation in fibromyalgia [144]. This evidence concerns the gene HK1 and fibromyalgia.