Paneth cell metaplasia is the appearance of Paneth cells where they aren't normally found. The cells are most abundant in the small intestine. In a healthy person, they are also scattered at the start of the large intestine, and aren't seen in the rest of the organ. In some people with Crohn's disease or ulcerative colitis, however, Paneth cells have been discovered further along in the large intestine. The reason for this observation isn't fully understood.