Cluster Belly: A Variant of Irritable Bowel Syndrome

Cluster headache (CH) and irritable bowel syndrome (IBS) are pain disorders that possess relationships with circadian rhythms. However, they have not been compared to assess similarities that could yield pathophysiologic insights. A young male adult with periodic episodes of abdominal pain highly reminiscent of CH is described. Since childhood, he experienced severe attacks featuring excruciating, abdominal pain accompanied by prominent restlessness, lasting 30‐120 minutes, occurring in the evening and in discrete 2‐ to 8‐week periods, interspersed with remissions where typical triggers did not lead to attacks. Although all of the patient's symptoms fell within the spectrum of IBS, the semiology was highly evocative of CH, based on the attack duration, restlessness, periodicity, and selective vulnerability to particular triggers only during attack periods. A subset of patients thought to have IBS may feature similar attack profiles and could suggest the importance of the hypothalamus in its pathophysiology, akin to CH.