CHICAGO – Physicians can recognize mast cell activation syndrome by learning its associated triggers and symptoms, which affect many organ systems. Patients have good outcomes when they receive the appropriate pharmaceutical and dietary therapies, according to an overview presented at Freston Conference 2019, sponsored by the American Gastroenterological Association.
Mast cells are immune cells that originate in bone marrow. They defend against pathogens and contribute to tissue homeostasis and repair, said Matthew J. Hamilton, MD, associate gastroenterologist at Brigham and Women’s Hospital and assistant professor of medicine at Harvard Medical School, Boston.
Aberrant regulation, which may be perpetuated by persistent stimuli, can cause unwanted mast cell activation. Symptoms affect many systems simultaneously, such as the cutaneous (e.g., flushing, pruritis, and urticaria), digestive (e.g., abdominal cramping, diarrhea, reflux, and bloat), cardiovascular (e.g., hypotension, syncope, light-headedness, and tachycardia), and others. “These patients have a lot of morbidity due to these symptoms,” said Dr. Hamilton. Symptoms are episodic and result from predictable triggers. Their severity fluctuates. Alcohol, stress, heat, hot water, strong smells, medications, and foods are typical triggers for patients with mast cell activation syndrome. The foods that trigger symptoms vary greatly between patients, said Dr. Hamilton.
Patients have a typical presentation
On physical examination, patients often have flushing and dermatographia. Patients also may have tachycardia when at rest or when standing. Sites of abdominal pain or bloat and problems with concentration or memory also are common. Few biomarkers for mast cell activation syndrome have been identified. A blood test for mast cell tryptase and a 24-hour urine test for metabolites of histamine and prostaglandin should be ordered for every patient suspected of having the syndrome. “Ideally, you do baseline levels of these studies, and then repeat them when patients are symptomatic,” said Dr. Hamilton. “The tryptase really has to be done within hours of a reaction. That can be a challenge.” A subset of patients with mast cell activation syndrome have a baseline serum tryptase level greater than 11.4 ng/mL.
In 2010, Akin et al. proposed criteria for mast cell activation syndrome (J Allergy Clin Immunol. 2010;126:1099-104). A patient must have typical signs and symptoms of mast cell activation that affect two or more organ systems, as well as laboratory evidence of mast cell activation. A patient also must respond to medications that block mast cell mediators, and no other diagnosis should better explain his or her clinical profile.
As in the workup for other gastroenterological disorders, an endoscopy or colonoscopy is warranted to rule out other conditions such as inflammatory bowel disease, celiac disease, or disorders associated with intestinal eosinophilia. These procedures also can evaluate patients for systemic mastocytosis, the clonal form of mast cell disorders. In general, endoscopy is normal and reveals no specific features in patients with mast cell activation syndrome, said Dr. Hamilton. Histopathology generally is normal, as well. One study indicated that the mean number of mast cells did not differ between patients with mast cell activation syndrome, patients with irritable bowel syndrome (IBS), and healthy controls. Current studies are evaluating subsets of patients with mast cell activation syndrome who have increased numbers of mast cells noted per high power field to determine the utility of quantifying mast cells on histology in patients suspected of having this disorder.