660 Mast Cell Activation Syndrome- A Newly Recognized Cause of Recurrent Acute Abdominal Pain

Abstract

Background: Patients with mastocytosis or IgE-mediated disorders (ie. food allergy, anaphylaxis) have well characterized gastrointestinal symptoms that may include episodes of abdominal pain, bloating and diarrhea. There is a distinct population of patients, however, who do not meet criteria for mastocytosis and present with similar signs and symptoms. We have identified twenty-five patients in an adult gastroenterology clinic and characterized what is now known as Mast Cell Activation Syndrome (MCAS). Methods: We performed an ongoing review of 25 patients seen at Brigham and Women's Hospital with suspected MCAS from 2004-2009. This diagnosis was reached on clinical grounds based on a typical array of signs and symptoms as well as response to anti-mast cell mediator treatment (ie. mast cell membrane stabilizers, anti-histamines). Each patient had to have a history of abdominal pain, diarrhea and/or bloating and at least two objective findings of a mast cell related disorder such as flushing and dermatographism, or positive laboratory studies indicating mast cell mediator release (ie. 24 hour urine histamine and prostaglandin-D2). Response to anti-mast cell mediator medications was assessed by at least two physicians and graded based on the persistence of mast cell related symptoms (complete responseno further symptoms, excellent responseintermittent persistence of one symptom). Results: Results of all 25 patients are presented in the Table below. Conclusions: MCAS is an underrecognized cause of unexplained recurrent abdominal pain in patients who present to a gastroenterology clinic and frequently exhibit the constellation of clinical symptoms noted above. These patients may or may not have objective laboratory evidence of mast cell mediator release. It is important to be able to recognize this syndrome because response to anti-mast cell mediator medications is often dramatic.