What is MCAS?

In the last few years, the information around mast cell disorders has changed quite a bit. There is some confusion about what word is the ‘right’ one. It’s slowly coming together, and if will almost certainly change again many times. The terminology (if not the criterion) is slowly coming together and becoming more universal.. SO, I won’t go into depth here, and some of this is over-simplified. This is just a quick overview.

  • MCAD- Mast Cell Activation Disorders. This is the umbrella term for all mast cell diseases. I find it easier to remember if I think of the ‘Disorders”. The plural there tells you that it’s several things, not something specific.
  • MCAS- Mast Cell Activation Syndrome. A specific MCAD whereby an individuals mast cells release their histamine (degranulate) to a wide variety of triggers. The mast cells of these people are very sensitive, but there is generally a normal level of mast cells in the body.
  • Mastocytosis– an over-growth of mast cells, or the production of irregularly shaped mast cells. When used on it’s own, it usually refers to myloproliferative mastocytosis (coming from the bone marrow). There are several subtypes of mastocytosis, including ones that involve over production of mast cells in the bone marrow, skin, etc.

In general, patients with any kind of mast cell activation disorder can be widely variable. Mast cells are present in almost every organ in the body. Depending on which mast cells are involved, the symptoms can be very, very different. ANd yet somehow, they are easy to pick out of a crowd.

Diagnosing these conditions, is usually a long, difficult process. There aren’t any quick blood tests, the symptoms can be so varied, and often very difficult to ‘tease out’. Add in a disorder that looks very different from patient to patient and day to day. Some conditions, such as SM are relatively well known by physicians, and even by a few people in the general population. MCAS, as it has only recently been something that can be verified by blood and urine tests, is less well known, but likely far more prevalent in the population. There is not yet a consensus about specific diagnostic criteria or incidence (how many people have it), but early research is showing that at least 10% of the broader population have som kind of mast cell disfunction.

Links to a number of disorders are being established, (Ehlers Danlos Syndrome, POTS, ME, CFS, ASD, etc…). The research is fast and furious, I can’t keep up (and it’s not where I choose to focus, to be honest). If you would like references, and or something printable to take to your doctor, there are several good resources on the web. This is a good place to start:

TMS The Mastocytosis Association (based in the US). tmsforacure.org. It has been recently re-vamped, and it has some very useful reseources, such as this informational pamphlet.

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