A paucity of colonic enteroendocrine and/or enterochromaffin cells characterizes a subset of patients with chronic unexplained diarrhea/malabsorption.

A generalized absence of enteroendocrine cells characterizes 2 diarrheal/malabsorptive diseases, namely, enteroendocrine cell dysgenesis and autoimmune polyglandular syndrome 1. However, it is not routine for pathologists to examine mucosal biopsies for enteroendocrine cells in cases of chronic diarrheal illness. Our primary aim was to prospectively examine colonic mucosa for loss of enteroendocrine cells using chromogranin A immunohistochemistry for diagnostic purposes. Our secondary aim was to investigate enterochromaffin cells as a subset of enteroendocrine cells, using serotonin (5HT) immunohistochemistry; we hypothesized that other causes of diarrhea due to loss of enteroendocrine cell subsets are missed by evaluating enteroendocrine cells alone. Our approach was limited to patients with chronic unexplained diarrhea partly selected by referring physicians who considered the patients problematic. Seven problematic patients with reduced enteroendocrine or enterochromaffin cells were collected over a 9-month period and placed in group A. Three group A patients demonstrated reduced enteroendocrine cells relative to controls, and they were later diagnosed as having enteroendocrine cell dysgenesis (n = 1) and autoimmune polyglandular syndrome 1 (n = 2). Four group A patients had reduced enterochromaffin cells but normal enteroendocrine cells. These 4 patients had conditions such as congenital diarrhea, mild graft-versus-host disease, acquired childhood chronic diarrhea, and diarrhea post lung transplant. The reduced enterochromaffin cells in the graft-versus-host disease patient inspired a third aim, that is, to investigate whether a loss of enterochromaffin cells would be a generalized defect seen in patients with mild colonic graft-versus-host disease (group B). However, no loss of enterochromaffin cells was detected in group B. Two methods of enumerating endocrine cells were used and demonstrated 67% agreement.