What clinical condition is associated with pigment macrophages in the lamina propria during colonoscopy?

The presence of pigment macrophages in the lamina propria during colonoscopy is most commonly associated with factitious diarrhea. This phenomenon occurs when individuals deliberately induce diarrhea, which can lead to the accumulation of pigment-laden macrophages due to the passage of blood or other pigments through the gastrointestinal tract. These pigment macrophages indicate a form of tissue reaction often seen in cases of repeated irritation or injury to the bowel lining.

In contrast, ulcerative colitis and Crohn's disease exhibit distinct histopathological features. Ulcerative colitis typically shows inflammatory changes, such as crypt abscesses and a loss of the colonic mucosal architecture, without significant pigmentation of macrophages. Crohn's disease, on the other hand, may demonstrate transmural inflammation and granulomas, also lacking the pigment macrophage characteristic that is specific to factitious diarrhea.

Diverticulitis could present inflammation and microabscesses in the colon, but again, pigment macrophages would not be a defining feature of this condition.

Thus, the presence of pigment macrophages in the lamina propria is a unique marker of factitious diarrhea, differentiating it from the other conditions listed.