Mast Cell Activation Syndrome

What is Mast Cell Activation Syndrome?
Mast cells, a type of blood cell, play an important role in the body’s immune system. They reside in all body tissues and form part of the body’s initial defense system. Mast cells react to foreign bodies and injury by releasing a variety of potent chemical mediators, such as histamine, when activated. In a healthy person these chemicals will act beneficially to protect and heal the body, but in a person with MCAS these same chemicals are inappropriately triggered and released and have a negative effect on the body. Among the triggers are a variety of different foods, exercise, chemicals, fragrances and stress. Many sufferers struggle to identify their triggers and continue to discover new triggers for many years after diagnosis.

MCAS forms part of a spectrum of mast cell disorders involving proliferation and/or excessive sensitivity of mast cells, it has been identified since 2007. It features inappropriate mast cell activation with little or no increase in the number of mast cells, unlike in Mastocytosis*. MCAS causes a wide range of unpleasant, sometimes debilitating, symptoms in any of the different systems of the body, frequently affecting several systems at the same time. The onset of MCAS is often sudden, affecting both children and adults, sometimes in family groups, mimicking many other conditions and presenting a wide-range of different symptoms that can be baffling for both the patient and their physician. Often there are no obvious clinical signs since MCAS confounds the anatomy-based structure underpinning the traditional diagnostic approach. Very often Mast Cell Activation Syndrome is hiding in plain sight.

MCAS presents through a wide range of symptoms in multiple body systems, ranging from digestive discomfort to chronic pain, mental health issues and anaphylaxis.

Some key aspects of MCAS are:

  • The symptoms impact more than one body system.
  • People often experience a dramatic step change in symptoms after, perhaps, years of mild symptoms.
  • The symptoms are often episodic or cyclic and wax and wane with varying degrees of intensity, sometimes worsening over time.
  • There is often histamine involvement and will therefore include typical allergy symptoms such as itching, rashes, swelling, inflammation and vomiting.
  • The triggers are many and varied some easily recognized some not, among them environmental chemicals, foodstuffs, heat, cold and exercise.
  • MCAS can present simultaneously in patients who have Ehlers Danlos Syndrome (EDS) a connective tissue disorder, and/or Postural Orthostatic Tachycardia Syndrome (POTS).

The available treatments for MCAS stabilize the mast cells and mitigate the effects of the chemicals they release, e.g. anti-histamines and mast cell stabilizers. Avoiding triggers is also a key part in coping with this illness. See Support and Resources for publications.

There is a wide range in the variety of patients’ response to treatment. It can often take some time to work out what the best medication and dosage are. An added complication is that many patients suffer adverse reactions to the drugs themselves or to the fillers, colouring and preservatives. With a trial and error approach many patients are successful in moderating their symptoms although quality of life can still be affected.


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