Mastocytic enterocolitis

Mastocytic enterocolitis was first named in 2006, referring to the phenomenon of having increased mast cells in the mucosa of the GI tract.  Patients generally present with chronic diarrhea and abdominal pain.  This disorder is distinct from other types of Irritable Bowel Syndrome, which often has similar symptoms.  The increase in mast cells is not associated with SM or CM.  Patients generally respond to mast cell medications. 

The original study included 47 patients.  Only some patients were tested for serum tryptase, but among those who were, all had normal tryptase values.  43/47 patients had normal endoscopies, with the other 4 showing some swelling in the GI tract.  In 34 patients, H&E staining was either normal or showed a small, local increase of inflammatory cells.  In the other 13, a mild increase of inflammatory cells was seen.  It is important to note that abnormalities that might point to another disease, including crypt distortion, mucin depletin, cryptitis, crypt abscesses, granulomas, thickened collagen band, excessive eosinophils, increased intraepithelial lymphocytes, shortened duodenal villi, parasites, and viral inclusions, were all absent. 

Patients with a known inflammatory bowel disease had an average of 12.4 mast cells per high powered field (hpf.)  Health controls had an average of 13.6 mast cells/hpf in the colon and 13.2 mast cells/hpf in the duodenum.  Of the patients in the study group, 33/47 had increased mast cell counts in the small or large intestines, with an average of 25.7 cells/hpf.  60% of patients in this group had increased mast cells in both the duodenum and colon.  67% of patients had a significant reduction in diarrhea and abdominal pain when treated with antihistamines and mast cell stabilizers.

Mastocytic enterocolitis was defined as more than 20 mast cells/ hpf by tryptase staining in patients with chronic diarrhea of unknown origin.  These patients have high GI mast cell counts but their GI organs are NOT densely infiltrated by mast cells.  So a biopsy showing you have 33 mast cells/hpf in the duodenum or colon when you have chronic diarrhea generally gets you a diagnosis of mastocytic enterocolitis 

There has also been found to be a distinct group of patients with not only chronic abdominal pain, but also dysmotility, a history of food and environmental allergies, flushing, itching, tachycardia, asthma, headache, dermatographism, elevated IgE levels or whole blood histamine levels.  These patients reliably have mast cell counts in the duodenum or colon of more than 40 mast cells/ hpf.  This condition has been called allergic mastocytic gastroenteritis and colitis.  In these patients, the principle symptoms are abdominal pain, dysmotility, and waking in the middle of the night with the need to use the bathroom.  Patients may be constipated or have diarrhea. 

Some MCAS patients have been observed to have “borderline” mast cell counts in the GI tract, ranging from, 17-23/ hpf.  These patients have abdominal pain, dermatographia and flushing.  In MCAS patients studied, mast cell counts in the stomach range from 14-28, with an average of 17/ hpf; duodenum, 18-26, with an average of 23/ hpf; left colon, 15-27, with an average of 20; and right colon, 12-18, with an average of 17.  MCAS patients have more systemic symptoms and are diagnosed based upon the exclusion of all other mast cell diseases.

It’s important to note that the cutoff for “normal” mast cell count, 20 cells/ hpf, is somewhat arbitrary.  This came to be the standard when a 2011 paper used a previous paper, in which healthy controls had less than 20 cells/ hpf, was used as a reference standard.  There is a lot of debate over what constitutes a normal mast cell count throughout the GI tract.

References:

Shriram Jakate, Mark Demeo, Rohan John, Mary Tobin, and Ali Keshavarzian (2006) Mastocytic Enterocolitis: Increased Mucosal Mast Cells in Chronic Intractable Diarrhea. Archives of Pathology & Laboratory Medicine: March 2006, Vol. 130, No. 3, pp. 362-367.

Hahn, Hejin P., Hornick, Jason L.  Immunoreactivity for CD25 in Gastrointestinal Mucosal Mast Cells is Specific for Systemic Mastocytosis.  American Journal of Surgical Pathology. Volume 31 (11). 2007.

Hamilton, Matthew J, et al.  Mast cell activation syndrome : A newly recognized disorder with systemic clinical manifestations.  2011, Vol 128, Issue 1, pp. 147-152.

Akhavein, A, et al.  Allergic mastocytic gastroenteritis and colitis: An unexplained etiology in chronic abdominal pain and gastrointestinal dysmotility.  2012, Gastroenterology Research and Practice.