What is Mast Cell Activation Syndrome?

Mast Cell Activation Syndrome (MCAS) forms part of a spectrum of mast cell disorders caused by the abnormal proliferation, accumulation, function and/or activation of mast cells. It causes a wide range of unpleasant, frequently debilitating allergic and inflammatory symptoms in many different systems of the body.

People with MCAS can react to a wide range of triggers and potentiating factors including foods, chemicals, drugs, fragrances, temperature, exercise, stress, hormonal fluctuations and infection.

The onset of MCAS can be unpredictable, affecting both children and adults, and presents with a wide range of symptoms in multiple body systems, ranging from hives and rashes, respiratory problems, syncope, gastrointestinal pain, diarrhoea, reflux, neurological problems including anxiety and brain fog, bone pain, and anaphylaxis.

The complex, multisystem nature of MCAS can make gaining a diagnosis particularly challenging. The ability to gain a diagnosis is also negatively impacted by a lack of universally accepted diagnostic criteria and access to diagnostic biomarkers.

There is an urgent need to give a voice to patients, support doctors and researchers, and inform policy-makers about this widely under-recognised condition.

With your support, we feel confident that we can make a substantial difference to the lives of those affected by MCAS and their families.

You can read our collection of patient stories here.

Symptoms of MCAS

The symptoms of MCAS are often unpleasant, sometimes debilitating and can include life-threatening anaphylaxis. These symptoms usually involve multiple systems of the body and can include skin (dermatologic) symptoms, gastrointestinal symptoms (such as abdominal pain, nausea and vomiting), respiratory symptoms, neurological problems and urinary issues.

MCAS symptoms are often episodic or wax and wane (meaning that they go and come back) and their severity can fluctuate over time. In some cases, people may suffer mild symptoms for a long time before experiencing a sudden increase in the frequency or severity of symptoms. Possibly after a particularly triggering incident for the immune system, such as a severe infection or a medical procedure or operation.

Mast Cell Mediators

Mast Cells are tissue white blood cells, found in all parts of the body

They are functionally and phenotypically heterogeneous. They are a key part of the innate immune system with a role in immune defence, patrolling linings of mucosal surfaces of organs: the host-environment interface

In response to triggers mast cells release a range of mast cell mediators. (See image to the left)

Comorbidities

Observational studies and patient-reported data show ‘clustering’ of MCAS with other conditions, meaning that people who have MCAS often also have at least one additional condition.

Common comorbidities include connective tissue disorders, e.g. Ehlers Danlos Syndrome (EDS) and Marfans, dysautonomia, such as postural orthostatic tachycardia syndrome (POTS), and type 2 diabetes. The relationship between MCAS and many of these comorbidities is yet to be fully understood, and more research is required.

Further information on comorbidities can be found in the Royal College of GPs Ehlers Danlos Syndromes Toolkit. 

As you can see from the image on the left, Long COVID subjects & those with MCAS prior to treatment, had identical symptoms. Furthermore, MCAS symptoms increased in Long Covid patients, similar to those who have MCAS. ​

​Conclusion: activation aberrant mast cells was induced by SARS-CoV-2 infection and may underlie part of the pathophysiology of long covid, suggesting routes to effective treatments

Mast cell activation symptoms are prevalent in long covid Weinstock  L, Brook J, Afrin L, Molderings G. Int Journal of Infectious Diseases. 2021;112:217-226

Professional Network

If you are treating patients with MCAS or suspected MCAS or are interested in treating patients with MCAS, please register your details with us here. We are passionate about connecting healthcare professionals to share knowledge and collaborate. Mast Cell Action believes together we can enhance research, education, and awareness and ultimately improve the quality of life for those living with mast cell disease.

Join our professional network to:

• Receive important news and updates
• Get invites to dedicated HCP events
• Get updates about resources for patients
• Have optional listing on our database of HCP's - Opt in required

Useful presentations

Presentations given by Dr Alex Croom and Dr Bethan Myers at the 2019 PoTs Masterclass in the UK for more information on MCAS. 

Presentations given by Dr. Anne Maitland from the ICAHN school of medicine at Mount Sinai in the US:

• EDS Virtual Summer Conference 2020: Treatment of Allergy and Immunology Issues 
• Bobby Jones Chiari & Syringomyelia Foundation Educational Lecture Series 2019: Mast Cell Activation Syndrome 

Dr. Theoharis Theoharides explains more about mast cells and the role of mast cell activation in the immune system.