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Mast Cell Activation Syndrome & Low Blood Volume


Two symptoms occur frequently in people with ME/CFS: Mast Cell Activation Syndrome (MCAS) and low blood volume. What if these are not coincidental?

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People with ME/CFS have less blood than we should. We have low blood volume. We also tend to have a condition called mast cell activation syndrome or MCAS. I think these may not be two separate events. I think they may be closely linked.

MCAS stands for mast cell activation syndrome. Mast cells act as sentinels that detect injuries, infectious agents, decrements in blood supply or other changes in the body. They are early or first responders to many potentially dangerous situations.

In MCAS, mast cells become hypersensitive and chronically active.  Somehow they start to identify innocuous things like common foods, hot weather, smells, normally safe chemicals or even sunlight as dangerous.

Chronically activated mast cells are a problem because mast cells release a roster of bad actors that would make anyone feel sick. In my experience, my MCAS is inseparable from my ME/CFS because reactions to foods reliably provoke all of my ME/CFS symptoms.

When I got ME/CFS as a teenager, I got MCAS. If doctors had known what they were looking for, I would have immediately been identified as an MCAS patient. I flushed hot all the time in my face and ears and started getting hives like giant mosquito bites on my face. This happened every time I ate, for hours afterwards, every day.

When I developed ME/CFS, I also developed disturbingly low blood pressure and had trouble holding myself upright for any length of time. This is called orthostatic intolerance. Recent research has shown that while ME/CFS patients overall tend to have low blood volume, ME/CFS patients with orthostatic intolerance have markedly low blood volume.  Very low blood pressure is a normal consequence of low blood volume.

Indeed, I am one of the many, many ME/CFS patients who feels much better when I increase my blood volume. Increasing blood volume is likely the most universal treatment for ME/CFS currently, given that we have no approved medications for the disorder.

These two events, low blood pressure and MCAS occurred suddenly and at the same time in me.  They occurred at the same time that I developed the crushing fatigue and exercise intolerance that characterizes ME/CFS.

Let’s look at possible connections between these two events.

Blood volume loss causes inadequate perfusion of the tissues in the body.  In the recent study of ME/CFS patients with and without orthostatic intolerance, the patients with orthostatic intolerance were on average 20% low in blood volume. The reference value for blood volume in this study was 70ml/kg.  The orthostatic patients had an average blood volume of 56 ml/kg.

If you are healthy and you suddenly lose more than 15% of your blood volume, you would swing right past stage I shock and enter stage II shock. Patients with ME/CFS and orthostatic intolerance thus have a level of blood volume consistent with stage II shock.

Shock is a state of impaired blood perfusion in the body, meaning that organs, as well as individual cells, don’t get enough blood or oxygen. With the degree of blood volume reduction that I likely have and that many people with ME/CFS have, there is likely to be chronically inadequate blood flow to the tissues of the body.

What does our blood flow look like exactly?  The answer matters.

Shock from sudden loss of blood volume is “an ischemic insult against an entire organism” as one set of researchers put it in a 2018 paper. Ischemia is the denial of normal amounts of blood flow to tissues.

The necessary treatment for shock from low blood volume is to increase blood volume. Yet when you increase blood volume after losing blood volume, instead of a body-wide state of ischemia, you have something different and something that is in many ways more dangerous.

The influx of blood after blood deprivation causes an explosion of damage called ischemia-reperfusion injury. Ischemia-reperfusion injury entails a great deal of oxidative stress.  People with ME/CFS have chronically high oxidative stress for reasons no one has yet pinpointed.

Do we, with our chronic low blood volume, experience ischemia or do we experience ischemia and reperfusion? As we lay down and sit up, as we walk or sit still, as we drink more or less water, as days, weeks, months and years pass, what happens to any given cell?  At a microscopic level, our individual cells likely experience a variable level of perfusion, chronically inadequate, but at times more blood flow and at other times less blood flow. A situation reminiscent of bodywide ischemia and reperfusion.

Mast cells are present in the blood vessels of the body. Under conditions of ischemia-reperfusion, mast cells sense danger and activate. In fact, mast cells are responsible for much of the damage that occurs in ischemia-reperfusion injury.

Do prolonged problems with perfusion cause or help maintain MCAS? Does this account for the fact that I developed MCAS and low blood volume at the same time?

Further, does this come full circle?  If low blood volume can trigger MCAS, can MCAS reduce blood volume?

When I have a mast cell reaction, I pee and pee and pee.  I drink 8 ounces of water and pee out 8 ounces of clear liquid twenty minutes later. My blood pressure is rock bottom, but I can’t seem to retain fluids. I’m not the only one. Mast cell reactions in people with POTS, an autonomic nervous system disorder tied to ME/CFS, low blood volume and MCAS, also pee a lot when having mast cell reactions. 

Do low blood volume and MCAS form an inescapable loop in some people?