Chronic excess of BDNF in the KIV intestine may lead to irritable bowel syndrome (IBS), a chronic disorder characterized by recurrent abdominal pain, visceral hyperalgesia, and abnormal bowel movements (Enck et al. 2016), as indicated by previous research reporting increased BDNF expression in IBS patients and its positive correlation with abdominal pain and disease severity (Yu et al. 2012; Zhang et al. 2019). The gene discussed is BDNF; the disease is irritable bowel syndrome.