IL1RN and irritable bowel syndrome: Other genes may affect these disorders through other mechanisms, such as recent findings of SCN9A allele described above influencing interstitial cystitis/bladder pain syndrome [160]; functional alleles in interleukin-1 receptor antagonist (IL1RN) and melanocortin-1 receptor (MC1R) genes increasing the risk of VVS [161]; or proinflammatory cytokine gene polymorphisms in IL-6 and TNF-α changing individual susceptibility to IBS [162].