I belong to a few different mast-cell related support groups, which have been super helpful to me along the way.

From reading posts there, it seems as though it’s far too common for people to end up in a scenario where they have symptoms of mast cell disease, but aren’t sure whether it’s mast cell activation syndrome, or another form of mast cell disorder such as mastocytosis.

And, unfortunately, since there are so few doctors out there who really seem to have experience in treating mast cell disorders, patients in this situation often don’t know where to turn.

So I wanted to let you all know that Dr. Castells was able to order a test for me that really helped to determine that I have mast cell activation syndrome, as opposed to mastocytosis.

Unfortunately, I’m not sure how widely available this test is, as Dr. Catells the only doctor I’ve met who can order it (this was at the Mastocytosis Center at Brigham and Women’s Hospital) but I did want to let you all know that it’s a potential option.

It was a blood test to check to see if your mast cells have a genetic mutation called the KIT D816V mutation.

If you have this mutation, it’s a sign that you have a specific genetic mutation in your mast cells that has been found in patients with mastocytosis.

There can also be a form of mast cell activation that can be caused by this genetic mutation, called primary mast cell activation (sometimes also called monoclonal mast cell activation).

Because my KIT-mutation test came back negative, Dr. Castells was able to conclude that I have secondary mast cell activation– which means that it’s not specifically caused by a genetic mutation, rather it’s triggered by a specific event or another medical condition.

This means, thankfully, that the kind of MCAS that I have is the kind that can actually go away, if you’re able to change the event or condition that triggered it in the first place.

If the KIT-mutation test had come back positive, Dr. Castells’ next step would have been to order a bone marrow biopsy, which can be used to differentiate between the different types of mastocytosis.

Thankfully, the conclusion here was that I have secondary mast cell activation, and did not need the biopsy.

I will be talking more about the different types of mast cell activation in further posts.

For now, here are some references for the concepts I talked about in this post:

Article from the Mastocystosis Society on the three types of mast cell activation.

Nature article on the KIT-mutation