“Mast”ering the Evaluation of Chronic Diarrhea

Abstract

Case: A 39-year-old Chinese female with no PMHx presented to our office with complaints of worsening diarrhea over the last 6 months. She complained of 4 - 6 watery bowel movements daily. She denied blood in the stool, abdominal pain, or weight loss. She noted no change in appetite or diet and no new medications. She has a significant allergy history for almonds, eggs, and peanuts. Stool studies were negative and the physical exam was benign. A colonoscopy revealed normal mucosa. Multiple random biopsies from the colon and rectum revealed increased mast cells in the lamina propria (>50 /HPF) consistent with mastocytic enterocolitis. Discussion: Mastocytic enterocolitis describes patients with diarrhea who have what pathologists have interpreted as an increased number of mast cells in the colon and lower duodenum. Mast cells have a role in the allergic hypersensitivity type I reaction and are rich in gastrointestinal mucosa, enabling their immune function to environmental substances. As mastocytic enterocolitis can be a manifestation of systemic mastocytosis, an attempt to establish whether this is the case through bone marrow biopsy can be justified. It has been proposed that a screening for an 816V mutational analysis on the peripheral blood can also be considered. However, mastocytes can also be increased in other GI diseases including IBS where they have been found in the cecum, TI, and jejunum. Though there is no definitive treatment for the condition, various medications such as H1/H2 antihistamines, cromolyn sodium, antileukotriene agents, and budesonide have all been tried with varying success. The fortuitous diffuse mucosal distribution of mast cells throughout the lamina propria perfectly suits the type of tissue sample obtainable on random endoscopic biopsy specimens. Physicians managing patients with chronic intractable diarrhea should be encouraged to incorporate endoscopy, random colonic or duodenal mucosal sampling, and immunostaining as part of their investigational protocol. If increased mast cells are found, physicians should consider therapeutic options that alter mast cell mediator release and function. As mast cell populations can demonstrate fluctuations, investigations are best performed during active symptoms and before treatment. Further studies in this area should elucidate clinical subclasses of disorders with distinct immunologic or central nervous system triggers for mucosal mast cell proliferation and mediator release.