What is MCAS?

What does MCAS stand for?

Mast Cell Activation Syndrome.

What are mast cells?

First off, everyone has them. Mast cells are a type of white blood cell that exist in many tissues in the body. Inside mast cells, there are numerous granules surrounded by membranes. These granules hold mast cell mediators/chemicals including (but not limited to) histamine, prostaglandin, and tryptase.


What do mast cells do?

Mast cells are best known for their role in allergy response and anaphylaxis. However, they also help with defense against microbes and parasites, blood vessel creation, wound healting, clotting, and regulation of reproductive activities, to name a few. Mast cells use the mediator chemicals in their granules to carry out their various jobs.

When triggered, mast cells activate; meaning they release the mediator chemicals from their granules. This process is also called “mast cell degranulation.”

In healthy people, mast cells degranulate and release mediator chemicals appropriately to carry out the job intended of the mast cell (e.g. defense against pathogens, etc.)

What is Mast Cell Activation Syndrome?

Mast Cell Activation Syndrome (MCAS) is when mast cells inappropriately release mediator chemicals, causing symptoms. Like mentioned above, mast cells degranulate appropriately in response to true threats in healthy people. However, in people with MCAS, their mast cells degranulate in response to triggers that should not be perceived by the body as harmful.


Symptoms can include, but are not limited to: fatigue, inflammation, swelling, anaphylaxis, rashes, itchiness, hives, burning sensations, brain fog, cognitive problems, vision problems, muscle pain, joint pain, urogenital problems, and gastrointenstinal issues.


Also, MCAS is commonly found in patients with Postural Orthostatic Tachycardia Syndrome and/or Ehlers-Danlos Syndrome.

Does MCAS have a cure?

No. However, there are medications that people can take that may reduce symptoms.

What should I do if I think I have MCAS?

I highly recommend reading “Never Bet Against Occam” by Dr. Afrin. He is a MCAS specialist and this book really highlights all the different and weird symptoms and journeys to diagnosis. I found it very helpful when I first heard that some of my symptoms could be attributed to MCAS.

Also, you need to find a doctor who knows about MCAS. You can do this by calling and asking (usually if they do not response with a very certain “yes,” I would not recommend seeing them), asking on MCAS Facebook groups (just search for MCAS groups on FB and you should be able to find them), or directly messaging people on Instagram who have MCAS (you can search #MCAS or #MastCellActivationSyndrome to find accounts). MCAS is not a widely known disease, so it can be hard to find good doctors who know about it. I’ve found it’s mainly word of mouth and through the use of social media.

Once you find a doctor, you need to make sure they do the correct tests. Tests usually include a blood test for tryptase, histamine, and prostaglandin as well as a 24-hour urine collection for N-methylhistamine and prostaglandin that must be refrigerated in between collections and put on ice to be sent off to the lab. Testing for MCAS can be tricky, so it is very important that you keep the sample cold.

For more information on testing, go to The Mastocytosis Society has a pretty good overview.

Image result for mcas infographic