MUC5AC and cyclic hematopoiesis: Patients with CN were categorized into two clinical/endoscopic subtypes: one group manifested MC‐like symptoms (watery diarrhea) with minimal endoscopic abnormality, while another group is featured by IBD‐like symptoms (occult/gross hematochezia, abdominal pain or mucin secretion) with patchy reddening of the colorectal mucosa with or without erosion/aphtha.