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Mast Cell Activation Syndrome (MCAS)

Mast Cell Activation Syndrome (MCAS)

When we evaluate patients with gastrointestinal symptoms who also present with symptoms relating to other body systems, we consider a disease called mast cell activation syndrome (MCAS).


What is Mast Cell Activation Syndrome?

Mast cell activation syndrome (MCAS) is a condition in which mast cells excessively and frequently release products called mediators into the body causing allergic-type symptoms at inappropriate times. This causes patients to experience repeated episodes of allergic symptoms that affect different systems of the body.

In more detail, mast cells are immune system cells that are found in the body’s bone marrow and body tissues. Typically, mast cells have a role in protecting the body from infections and inflammatory responses; they are also responsible for allergic reactions. When mast cells are triggered or activated by allergens or other substances, they produce an allergic reaction by quickly releasing mediators stored inside sacs of the cells.


Symptoms of MCAS

Symptoms can occur in multiple body systems and vary in severity and duration.


Diagnosis of MCAS

Diagnosing MCAS can be difficult as there are many overlapping symptoms with various conditions and there is not one definitive diagnostic test. However, there are urine and blood tests that can be performed to provide clues for a diagnosis of MCAS. Such tests include a blood test for tryptase levels and a 24-hour urine test for N-methylhistamine and prostaglandin. A thorough review of a patient’s medical history is also helpful in diagnosing MCAS by ruling out other potential diseases.


Treatment for MCAS

There is no cure for this disease. Instead, current available treatments for MCAS stabilize the effects of mediators released by mast cells which help manage symptoms. Treatments include:



Fiona Miao Patient Care Coordinator

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