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July 2017

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 47

  1. 58. What is mastocytic enterocolitis?

A high powered field (hpf) is what you see through a microscope when you use powerful magnifying lenses. With very few exceptions, high powered fields using the same lenses are the same size. Since they are the same size, you can directly compare results from various groups all over the world.

In 2006, a paper was published that coined the term “mastocytic enterocolitis”. The author described mastocytic enterocolitis as more than 20 mast cells per high powered field. This paper was about people with severe chronic diarrhea that did not improve with treatment. The author found that healthy people had about 13 mast cells/hpf while people with severe chronic diarrhea had about 20 mast cells/hpf. The author felt that the extra mast cells were responsible for the diarrhea and inflammation so they called the extra mast cells in the colon and the small intestine “mastocytic enterocolitis”. Enterocolitis is the term for inflammation in the small intestine and colon.

The author felt that 20 mast cells/hpf was the cutoff between a normal amount of mast cells in the GI tract and an abnormal amount. Under 20 was considered normal while 20 and above was considered abnormal. However, there have been a number of papers since that look at how many mast cells are present in the GI tract for patients with different conditions as well as healthy people. There are several conditions that can cause you to have 20 or more mast cells/hpf. (I wrote an exhaustive series on this in 2015-2016. Links are below.)

Additionally, in some situations, people have over 20 mast cells/hpf without having any symptoms. Sometimes healthy people without any GI conditions have over 20 mast cells/hpf. For this reason, there is not agreement about how many mast cells in the GI tract is too many. (If you’re looking for my opinion, I think the number for what is too many is around 25-30/hpf. This is just my opinion.)

In the last several years, some doctors have begun linking mastocytic enterocolitis to mast cell disease. This makes sense because we know that in those people, mast cell inflammation drives GI symptoms and damage. Mast cell patients certainly have a lot of inflammation in the GI tract so having extra mast cells there makes sense. Some experts think that mastocytic enterocolitis is a sign of mast cell activation syndrome and that patients with mastocytic enterocolitis all have mast cell activation syndrome.

Mastocytic enterocolitis is absolutely a real phenomenon. In these people, mast cells cause a lot of GI symptoms and damage the GI tract. Experts have not all agreed upon whether or not everyone with mastocytic enterocolitis has mast cell disease. Also, there are some researchers that feel that mastocytic enterocolitis is actually its own mast cell disease rather than just a feature of another mast cell disease like mast cell activation syndrome.

Currently, mastocytic enterocolitis is not recognized by the WHO as its own disorder. However, that could certainly change. It was only last year that MCAS was recognized by the CDC even though it was routinely recognized by researchers and providers. (Author’s note: This was initially published stating that the WHO recognized MCAS, rather than the CDC. MCAS has not yet been recognized by the WHO. This is a whopper mistake on my part. Many thanks to the reader who saw this. Sorry!) I personally expect this to change in the next few years as more mast cell patients are diagnosed and mastocytic enterocolitis is better recognized. I think it is suggestive of mast cell disease but I also think providers need to eliminate other possible causes for the extra mast cells in the GI tract.

For more detailed information, please visit these posts:

Mast cells in the GI tract: How many is too many? (Part One)

Mast cells in the GI tract: How many is too many? (Part Two)

Mast cells in the GI tract: How many is too many? (Part Three)

Mast cells in the GI tract: How many is too many? (Part Four)

Mast cells in the GI tract: How many is too many? (Part Five)

Mast cells in the GI tract: How many is too many? (Part Six)

Mast cells in the GI tract: How many is too many? (Part Seven)

Mast cells in the GI tract: How many is too many? (Part Eight)

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 45

54. How does mast cell disease affect clotting?

Heparin is a very potent blood thinner and inhibits the body’s ability to form clots.  Mast cells are full of heparin. Mast cells stores chemicals like heparin in little pouches inside them called granules. In the granules, histamine is stuck to heparin. This means that when mast cells open their granules and release histamine, heparin comes out with it. This can contribute to things like bruising or bleeding more than expected.

Mast cells release other chemicals that can affect clotting. Platelet activation factor and thromboxane A2 both encourage the body to make clots. Some chemicals that help to regulate when to make a clot can activate mast cells, like complement C3a and C5a.

55. How many people have mast cell disease?

It is hard to know exactly how many people have a rare disease because they are not reported if they are recognized and correctly diagnosed. As recognition and diagnosis improves, rare diseases are often found to be more prevalent than previously thought. The numbers below are current estimates.

Systemic mastocytosis is thought to affect around 0.3-13/100000 people. In one large study, indolent systemic mastocytosis (ISM) makes up 47% of cases. Aggressive systemic mastocytosis (ASM) has been described in various places as comprising 3-10%. Systemic mastocytosis with associated hematologic disease could count for as many of 40% of cases of SM. Mast cell leukemia is extremely rare and accounts for less than 1% of SM cases.

Systemic mastocytosis accounts for about 10% of total mastocytosis cases. This means that total mastocytosis cases come in at around 3-130/100000 people. The remaining 90% of mastocytosis cases are cutaneous with incidence roughly around 2.7-117/100000 people.

We do not have yet have a great grasp upon how many people have mast cell activation syndrome (MCAS) but from where I am sitting, it’s a lot and that number is likely to grow. We know that genetic studies have found mutations that might be linked to MCAS in up to 9% of the people in some groups. However, having a mutation is not the same thing as having a disease. As we learn more about MCAS, we will gain some clarity around how many people have it.

For more detailed reading, please visit the following posts:

Progression of mast cell diseases: Part 2

The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (ISM, SSM, ASM)

The Provider Primer Series: Natural history of SM-AHD, MCL and MCS

The Provider Primer Series: Cutaneous mastocytosis/Mastocytosis in the skin


The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 44

53.  How do I get effective care from providers that don’t know anything about mast cell disease?

One of the most frustrating and concerning issues for mast cell patients is the need for involved specialty care when there are only a handful of experts worldwide. Many of us need so much care that there could be dozens of providers involved. Obviously there are no hard and fast rules that will guarantee a positive interaction with providers that don’t know about mast cell disease, but I will tell you what works for me.

My general recommendations about how to increase your chances of good care from providers are as follows:

  1. Do not expect most providers to know about mast cell disease or how to treat it. Patients are often upset to discover that healthcare providers know nothing about mast cell disease or how to treat it. There are currently over 7000 rare diseases described in literature. About 25,000,000 Americans have at least one rare disease. That is a lot of rare. It is impossible to know the ins and outs of so many diseases. Furthermore, medical education in recent years hinges not upon knowing everything but knowing where to find the knowledge you need. It is less important for your provider to know about mast cell disease than it is to know where they can find reliable information about it.
  • I never expect any provider to have heard of mast cell disease because it made me so mad so often when I did. I also find that I feel less hostile towards providers when I don’t expect them to have prior knowledge about my diseases. Less hostility improves any interaction.
  1. Have a script prepared for when you meet a provider that you don’t know. This is what I say after we exchange pleasantries:
  • “Before we get started, I want to make sure that you know that I have a rare blood disorder called systemic mastocytosis. Have you ever seen a patient with that before?”
  • If they have seen a patient with it before, great! Either way, I say this next:
  • “The hallmark of mast cell disease is severe allergic reaction or anaphylaxis to a variety of triggers without the involvement of IgE. It would really help me a lot if you could be really clear about what you’re doing and exactly what medications or materials I am being given. Also, if I feel anaphylaxis starting, I will use my Epipen first and then call for help.” (Please note that I administer epi myself immediately as directed by my immunologist. Speak with your doctor to find out what is the best course of action for you.)
  • This script does several things. Firstly, it lets them know that I have a reasonable understanding of my disease and the risks I face. This makes me a partner in my care. Secondly, it gives the provider a clear understanding of my expectations. They understand that I expect them to tell me everything they are doing and what materials and medications they are using. They understand there is the risk of anaphylaxis and that I have been given an Epipen to manage that. They understand that I will use this first and then call for help. In particular, the part about the Epipen is really important. Patients sometimes run into trouble when they use their own Epipen because providers are not expecting that and don’t react to it well. This conversation helps to avoid such a confrontration.
  • If I have seen this provider before, but it has been a while, or I remember them as being particularly unaware of mast cell disease, my script is basically the same. Something like,
  • “I just want to remind you that I have a rare blood disorder called systemic mastocytosis. The hallmark of mast cell disease is severe allergic reaction or anaphylaxis to a variety of triggers without the involvement of IgE. It would really help me a lot if you could be really clear about what you’re doing and exactly what medications or materials I am being given. Also, if I feel anaphylaxis starting, I will use my Epipen first and then call for help.”
  1. If you have a scheduled appointment or test somewhere you have not been seen before, call ahead a week or two before the appointment. Leave a message for the provider or their surrogate asking them to call you. This is the script I use:
  • “Hi, my name is Lisa Klimas, and I have an appointment with Dr. Yahoo at Some Date at Some Time Somewhere. I was just calling to make sure Dr. Yahoo is aware that I have a rare blood disorder called systemic mastocytosis. This disorder can cause allergic reactions to common things so there are certain precautions for mast cell patients. I would appreciate it if you could call me at your earliest convenience. Additionally, my mast cell specialist Dr. Mast Cell is available at Dr. Mast Cell’s number if you have any questions or concerns.”
  • Once again, we are clearly communicating our expectations. This also gives them extra time to learn a bit about mast cell disease or consult with your specialist so that they are comfortable seeing you.
  1. Be pleasant. This is hard to do sometimes, especially if you are scared. But if you can do this, things go much smoother. Nobody likes to be told what to do, even if they need to. Nobody likes to feel stupid. Be respectful. They will be much more likely to view you as an intriguing rare patient as opposed to some bitchy lady with masto (not speaking from personal experience, of course.)
  2. Do not argue. This is so, SO difficult sometimes but it is critical that you do not argue. Mast cell patients require a degree of control in order to mitigate the risk of reactions or anaphylaxis. Once you start arguing, you are no longer in control. You have given that control up. You will be viewed as an adversary. That is not going to get you anywhere.
  3. If you break rule 4 or 5, apologize.
  4. Be knowledgeable about your disease. You are your own best defense against dangerous health situations. You do not have to know everything but you should know where to direct providers for the information they need.
  5. When you give information about your disease, it has to be correct. This is so, so important. If you do not know the answer to something, do not invent one. Just say that you don’t know and that you can find out, or suggest a place where they can get that information.
  6. Limit the drama and intrigue when you are telling providers about your disease. There is a very fine line between being informative and scaring them. Help providers to feel comfortable about treating you.
  7. Have handy literature to educate providers about mast cell disease and how to manage mast cell patients safely. The literature should be short and comprehensive. They are much more likely to read something if it’s short and to the point. I let them know if that they are interested in further resources that I can provide those as well. I personally prefer to email literature to providers but hard copies are okay, too.
  • There are a few concise, effective papers that are great for this. This paper by Molderings and Afrin is one of my favorites. This one by Valent is good, too.
  • There are also materials prepared by organizations that are helpful for this. The Mastocytosis Society has materials for providers. On this site, I wrote the Provider Primer series for this specific purpose.
  1. Know the premedication and rescue medication protocols by heart. Also carry them in hard copy. You can find that here. If your protocols vary a lot from the general recommendations, ask for your doctor to write a letter describing your protocol that can be given to providers as needed.
  2. Know the difference between inconvenience and danger. This is critical. You have to know when a situation is dangerous and not just frustrating. There’s a big difference between refusing to give you epi during flagrant anaphylaxis and a provider making a stupid comment that being too hot can’t cause anaphylaxis. Your end game is always to get the care you need in a safe environment. Not every provider is going to be nice about your needs but if they are getting met, it’s not always worth it to argue.
  3. Remember that providers are doing their job. I have seen people report doctors who see multiple mast cell patients because the doctor was rude. I cannot stress enough that there is not a limitless pool of providers willing to treat mast cell patients. We do not want to give providers a reason to refuse to treat us. As much as possible, if you really can’t let a situation go, try to resolve it directly with the provider.
  4. Strongly encourage that your local providers establish a relationship with experts. This improves communication and encourages your local providers to seek help when they are unsure about how to help you.

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 43

52. Is it true that it can take up to six bone marrow biopsies to diagnose systemic mastocytosis?

Sort of. This has become sort of an urban legend in the mast cell community. I am partly to blame for this as I have offered this information up several times without explaining it, which is lazy on my part.

Systemic mastocytosis is diagnosed by biopsy. While a positive biopsy in any organ that’s not skin can be used to diagnose SM, bone marrow biopsies are overwhelmingly what is used to diagnose.

In 2004, a paper was published that discussed how well bone marrow biopsies worked for diagnosing SM in a group of 23 patients. These patients had bilateral bone marrow biopsies taken, so each patient had one on each side. In 19 of those patients, both of the biopsies showed mastocytosis. In 4 of those patients, only one of their two biopsies was positive. 4/23 is 17%, which is roughly 1/6. Based upon this figure, it means that theoretically, in a patient who has SM, they could have five negative biopsies before getting a positive biopsy.

It’s important to two things in mind when you think about this 1/6 thing. Firstly, this is a very small patient group. Things that you see in a small group don’t always translate to what really happens in larger groups. Another thing is that the criteria they used in 2004 to diagnose SM are not the same as the criteria we use now. It’s possible that with changes in diagnostic criteria that this 1/6 number is no longer accurate.

In reality, I have never met a person who needed six bone marrow biopsies to get a positive biopsy for SM. But I do know a few who needed two or three. It’s not impossible that it could take six to get a positive biopsy but it’s unlikely.

However, it’s also important to realize that every expert acknowledges that you can have a negative biopsy while having SM. The reason for this is that you can’t tell by looking whether or not a biopsy site will give you a positive biopsy for SM. You have to just hope that the mast cells are clustered where they stick the needle. Mast cells don’t cluster evenly throughout your bone marrow when you have SM. If you get a biopsy site where the mast cells didn’t happen to cluster, you are out of luck. For this reason, some doctors advocate getting bilateral bone marrow biopsies (two at once) to increase the chances of catching a positive biopsy.

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 42

51. What is the difference between mast cell activation syndrome and histamine intolerance?

Histamine intolerance is not widely accepted by the mainstream medical establishment. I haven’t been able to find much about it in the way of peer reviewed literature. That said, it doesn’t seem ridiculous to me. It feels plausible, I just haven’t seen convincing evidence of that yet.

Histamine intolerance is when a patient has symptoms from ingesting something that has a lot of histamine in it, that causes the body to release histamine, or that interferes with the body’s ability to break down histamine. In histamine intolerance, the problem is what is being put into your body rather your body itself. The problem is external, not internal.

Mast cell activation syndrome is when a patient’s mast cells are fundamentally dysfunctional. The problem is internal, not external. There is no evidence at this point that patients with MCAS can’t break down histamine normally with enough time, there’s just so much of it that it takes longer.

Many patients with MCAS (and other mast cell diseases) often have symptoms when they ingest something that has a lot of histamine in it or that causes the body to release histamine. There are two theoretical ways in which ingestion of histamine can cause symptoms: either the histamine released/ingested makes it way to other parts of the body and causes symptoms there directly; or, the histamine released/ingested makes mast cells release more histamine.

Regardless of exactly what is happening, patients with MCAS and histamine intolerance can have identical symptoms to ingesting a trigger. Importantly, MCAS patients may have histamine symptoms from lots of other things, not just ingesting something.

Histamine intolerance is much more commonly discussed in holistic and alternative medicine groups, which is definitely not where my expertise is. If you are aware of some recent data on histamine intolerance, or if I have made a mistake in this post, please let me know so that I can correct it.

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 41

50. How does mast cell disease affect hearing?

For readers who don’t know, I lost the majority of my hearing in 2009. I am profoundly deaf in my left ear and have moderate to severe hearing loss in my right. This happened years before I was diagnosed with systemic mastocytosis or Ehlers Danlos Syndrome.

Mast cell disease affects hearing in multiple ways. Some related diagnoses also affect hearing.

Mast cells are involved in sensorineural hearing loss. The exact role of mast cells is still being researched but hearing loss is not an unusual complaint for mast cell patients. Mast cell disease can also cause auditory processing disorder. This condition makes it difficult to understand speech. Ringing in the ears (tinnitus) is also a symptom of mast cell disease.

Many mast cell patients also have Ehlers Danlos Syndrome (EDS), a disease in which the body makes defective connective tissue. EDS patients are vulnerable to both sensorineural hearing loss, in which the nerves don’t correctly transmit sound from the ear to the brain, and conductive hearing loss, in which the ear is not able to carry the sound waves correctly to the inner ear. Having both types of hearing loss, sensorineural and conductive, is called mixed hearing loss.

Many mast cell patients are deconditioned. This means that their body has undergone lots of changes as the result of not being active. Sensory processing is affected in deconditioned patients. In particular, sounds must be louder to be heard correctly. POTS patients sometimes experience something similar.

Having certain autoimmune disorders can increase the risk of autoimmune inner ear disease, resulting in hearing loss. Many mast cell patients also have autoimmune disease.

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 40

49. What is the relationship between FPIES and MCAS?

FPIES is food protein induced enterocolitis syndrome, a severe type of food allergy. It causes continuous vomiting and diarrhea upon ingestion of a trigger. FPIES reactions can cause dehydration and dangerous drop in blood pressure. I cannot emphasize enough that FPIES can be extremely serious and that the reactions can be life threatening if they are not managed properly.

FPIES almost exclusively affects children starting in infancy and resolves around the age of 5. The reasons for this are unknown. FPIES is a diagnosis of exclusion. There are no tests to identify FPIES.

An important point is that trigger avoidance is generally sufficient for management in children with FPIES. When the child is not being exposed to a trigger, they should not have lingering symptoms.

If a child with FPIES continues to have symptoms, the conventional thinking is often that there must be a trigger that has not yet been eliminated from their diet. In children with continuing symptoms, they frequently have more traditional allergy type symptoms than the profuse GI issues seen with FPIES exposures. This is where FPIES starts to overlap with MCAS. MCAS can cause the same reactions to foods seen in FPIES. MCAS can also cause daily symptoms even if food triggers are avoided. Increasingly, children who were initially diagnosed with FPIES are later diagnosed with MCAS.

There are a few possible scenarios here. Firstly, it is possible that the child has FPIES and has MCAS secondarily to the FPIES. It is also possible that the child was misdiagnosed with FPIES and had MCAS all along. It may also be that FPIES is some form of MCAS. They have a lot in common.

Because there is no test for FPIES, and it is very difficult to accurately perform mediator testing to look for mast cell disease in infants, it is hard to be definitive at that age anyway. In some cases, investigation of MCAS as a possible diagnosis for these children only occurs when they fail to “grow out of” FPIES around age 5. Having anaphylaxis also provides a clue towards MCAS as a potential diagnosis.

For more detailed reading, please visit these posts:

Food allergy series: FPIES (Part 1)

Food allergy series: FPIES (Part 2)

Food allergy series: Mast cell food reactions and the low histamine diet

The Provider Primers Series: Mast cell activation syndrome (MCAS)

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 39

46. What does it mean to be a “leaker” or “shocker”?

These are terms patients use to describe the way mast cell disease affects them rather than defined medical terms. A leaker is someone who has a lot of symptoms day to day but has fewer severe attacks or anaphylaxis. A shocker is someone who has fewer day to day symptoms but more frequent severe attacks or anaphylaxis.

Leakers and shockers are not considered to have different subtypes of mast cell disease because symptom presentation varies hugely in all forms of mast cell disease. There are no tests to identify if you are a leaker or shocker. You can start a leaker and become a shocker or vice versa. The terms themselves have no medical meaning. They are just shorthand for patients to describe their experience with their disease.

47. What does “sense of impending doom” mean?

Sense of impending doom is the medical term for a feeling of terrible anxiety or fear, literally a feeling that something awful is about to happen. It is a medical symptom for lots of conditions, including anaphylaxis. The biological basis behind this sensation has been the subject of debate for a long time but there’s really no decisive answer as to the cause

48. Why do I taste metal when I’m having a bad reaction or anaphylaxis?

A metallic taste is also a symptom of many things, including anaphylaxis. It is also debated and an exact cause has never been identified. One of the more prevalent explanations is that it is the taste of epinephrine, which your body releases as an initial defense against anaphylaxis or mast cell degranulation. As far as I know, there is no data to support this.

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 38

45. Is mast cell disease autoimmune?

An autoimmune disease is the result of a patient’s immune system specifically targeting a normal, healthy part of their body. How particularly and precisely the immune system identifies part of the body to attack is very important to understanding my answer to this question.

Let’s look at some autoimmune diseases as examples.

Autoimmune thyroiditis (also called Hashimoto’s thyroiditis) is a prevalent autoimmune disease that targets the thyroid. The thyroid’s job is to make hormones that tell your body to do other things. These hormones are called thyroid hormones. When you have autoimmune thyroiditis, your immune system makes antibodies that target the thyroid and thyroid hormones. These are called autoantibodies. They target a normal part of body. There is no reason for the body to make these autoantibodies. They do not perform any healthy function for the body. The only function they serve is to attack part of the body.

When you have autoimmune thyroiditis, the immune system makes antibodies to things that are only found in the thyroid or made by the thyroid. (I’m being very general here.) Other autoimmune diseases target parts of the body that are found throughout the body so that the effects of the disease are more widespread. However, those diseases still target specific things.

Lupus is an autoimmune disease that affects many places in the body by precisely attacking things found throughout the body. The cells in your body all have DNA inside of them. This DNA has the genes to make proteins and other things your body needs. If the cell can’t use the DNA inside it correctly, it makes your body sick. This is exactly what happens in lupus. Lupus makes autoantibodies and attacks things inside your cells that your body needs to use the DNA. Because all of the cells in your body need to use their DNA, the things lupus attacks are found all over the body, not just one organ. But even though lupus attacks many organs and places throughout your body, it is still targeted to harm specific pieces of the body.

In autoimmune disease, the body makes specific things for the explicit purpose of damaging specific things.

Now let’s talk about mast cell disease.

Currently, mast cell diseases are not considered to be autoimmune by most – but not all – experts. (I’ll circle back to this.) When a person has mast cell disease, the fundamental issue is that they release tons of mast cell mediators at times when they shouldn’t, causing symptoms and damage to the body. But even though those chemicals can cause all kinds of problems, they are not targeted to attack specific structures. This is where the distinction is from autoimmune diseases. Mast cells release tons of histamine, but that histamine isn’t targeted to find a specific molecule inside of a liver cell. They release prostaglandin D2, but that PGD2 isn’t made for the particular purpose of attacking one particular thing inside of your thyroid.

Instead, the molecules released incorrectly by mast cells affect whatever cells are in its path. This is one of the reasons why there is such variability in symptoms and disease effects for mast cell patients. What parts of the body are affected the most is dependent upon a million things happening in the patient’s body. This is because the chemicals mast cells release are not targeted to any one place. They are just released by the mast cell and they go wherever they can before the body breaks them down.

I mentioned above that most experts did not consider mast cell diseases to be autoimmune, but not all of them. So let’s go back to that. Mastocytosis is not considered autoimmune but anyone as far as I am aware. There is absolutely no evidence that mastocytosis is autoimmune after decades of research. But MCAS is a newer entity and so there is less information on it due to less time spent researching it. There are still a lot of questions around MCAS and some experts think that whether or not it is autoimmune is one of them.

We know that at the very least that there is a connection between MCAS and autoimmune disease. Many MCAS patients have autoimmune disease, often more than one. We think MCAS occurs secondarily to the autoimmune disease in these patients. There’s also the fact that many MCAS patients are positive for ANA (antinuclear antibody), an autoantibody linked to lupus, even though they don’t have a diagnosed autoimmune disease that would cause that to be positive. Some people think that maybe MCAS is the autoimmune disease in that situation and that ANA is a marker indicating that MCAS is autoimmune. I have mentioned elsewhere that while we consider MCAS to usually be a secondary disease, there are some patients for whom we can’t find a primary disease. It is possible that MCAS is a primary condition in those people and that it is autoimmune.

You still need to keep in mind that even if we say that maybe the positive ANA shows that MCAS is autoimmune, there is still no evidence of any kind that indicates that mast cell mediators target a specific part of the body – a defining characteristic of autoimmune disease. That doesn’t mean there isn’t an autoantibody or some other mechanism for targeting precise structures in the body, just that we have no evidence of one existing right now.

Let’s recap: currently, most experts believe that mast cell diseases are not autoimmune because they do not target specific normal, healthy structures in the body. Mastocytosis is roundly agreed to not be autoimmune. There are some experts who feel that at least some cases of MCAS might be autoimmune. They feel this way because of the clear link between MCAS and other autoimmune diseases, as well as the fact that many MCAS patients are positive for an autoimmune marker, ANA, without evidence of an autoimmune disease that would explain that.