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monoclonal mast cell activation syndrome

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 83

96. Why are cancer drugs used to treat mast cell disease?

Disclaimer: The following post was written by me in my capacity as a subject matter expert in mast cell disease and author of MastAttack. This is not work product of my position as a Senior Scientist for a large research organization. All below statements are attributable directly to me in my role as author of MastAttack and are in no way attributable to my employer. Information presented here is publicly available and includes no confidential information learned in my capacity as a Senior Scientist for my employer.

  • There are a number of medications used to treat cancers that are also used to treat mast cell disease. Some of those medications are old school chemotherapies, some are newer, targeted chemotherapies, and some help to control the immune system.
  • In mastocytosis, the body makes too many mast cells. If the bone marrow makes way, way too many mast cells, and those mast cells don’t function correctly, the mast cells can act like cancer cells. This can cause the mastocytosis to behave like cancer.
  • Systemic mastocytosis has several subtypes. The least serious forms do not act like cancer.
  • Indolent systemic mastocytosis (ISM) is the least severe form of systemic mastocytosis. ISM has a normal lifespan. While patients with ISM are at risk of dying for anaphylaxis, an important distinction is that patients with ISM do not die because the mast cell disease acts like a cancer. ISM does not act like cancer.
  • Smoldering systemic mastocytosis (SSM) is a moderately serious form of systemic mastocytosis. SSM can shorten lifespan. In SSM, the body is starting to make lots more mast cells than it should. Those mast cells can affect how organs function. SSM acts like an early cancer.
  • SSM requires treatment to stop it from becoming a more serious form of mastocytosis called aggressive systemic mastocytosis (ASM) that acts like a serious cancer. The treatments used to manage SSM are also used in some cancer patients to help fight cancer. These include meds that affect your immune system, like interferon; newer targeted therapies and chemos, like tyrosine kinase inhibitors; and older chemo drugs, like cladribine.
  • Aggressive systemic mastocytosis (ASM) is a serious form of systemic mastocytosis. ASM shortens lifespan significantly. In ASM, the body makes way too many mast cells. The bone marrow churns out so many mast cells into the bloodstream and then the abnormal mast cells get stuffed into various organs. The mast cells cause organ damage and can cause organ failure. ASM is often referred to as being malignant because it behaves just like a cancer. It is also treated like a cancer.
  • As mentioned above, interferon is a therapy that can affect how the immune system works. Interferon is sometimes used for ASM but it is less commonly used in ASM than in SSM. ASM patients need more aggressive treatment. Newer targeted therapies like tyrosine kinase inhibitors and multitarget kinase inhibitors are frequently used in ASM. Some of these newer therapies are FDA approved for treating some ASM patients. Cladribine and hydroxyurea are still common treatments for ASM.
  • Mast cell leukemia (MCL) is the most serious form of systemic mastocytosis. MCL greatly reduces lifespan. MCL causes production of an unbelievable number of mast cells. There are so many mast cells that they cannot all get stuffed into organs like ASM. This means that while there are lots of mast cells in the organs in MCL patients, there are so many mast cells like that there are still tons of them in the bloodstream. This leads to rapid organ failure, leading to death. Mast cell leukemia is cancer. It is treated like cancer with newer therapies like tyrosine kinase inhibitors and multitarget kinase inhibitors, as well as hydroxyurea or cladribine in some cases. As in ASM, some of the newer therapies are FDA approved to treat mast cell leukemia.
  • Sometimes patients with systemic mastocytosis develop a second blood disorder. This is called systemic mastocytosis with associated hematologic disease. Sometimes this second blood disorder is a form of cancer, like chronic myeloid leukemia. In these instances, the other blood disorder would be treated using cancer medications.
  • Mast cell sarcoma (MCS) is a cancerous form of systemic mastocytosis. Patients with MCS rapidly develop MCL and are treated as described above.
  • None of the therapies I mentioned here are indicated for cutaneous mastocytosis. Cutaneous mastocytosis does not behave like a cancer and is not treated like one.
  • In recent years, two other forms of mast cell disease have been described: mast cell activation syndrome and monoclonal mast cell activation syndrome.
  • Monoclonal mast cell activation syndrome (MMAS) is often considered to be a “pre-SM”. It is treated like indolent systemic mastocytosis and does not behave like a cancer.
  • Mast cell activation syndrome (MCAS) is not know to be an early form of SM. Many people live with MCAS for decades without ever developing SM.
  • Despite the fact that mast cell activation syndrome, monoclonal mast cell activation syndrome, and indolent systemic mastocytosis do not behave like cancer, cancer therapies are sometimes used in these patients. They are used when other therapies have failed and their symptoms are still poorly controlled. Generally, they are used when persistent mast cell activation becomes life threatening. In some instances, they may be used when a patient’s symptoms are not life threatening but are very disabling and cause a poor quality of life. In these cases, the patient and their provider make the assessment that they are able to assume the risk of using these medications.
  • There is very little data on the use of chemo and targeted therapies in patients with MCAS, MMAS and ISM, and no cancer therapies are FDA approved for these conditions. However, use of cancer meds for nonmalignant conditions is not that unusual. It is pretty common in autoimmune disease where lower doses of chemotherapy drugs can be effective in controlling the disease. Basically, the idea is that if we know that these therapies help forms of mast cell disease that behave like cancers then it might help those forms that don’t act like cancer.
  • On a number of occasions, I have seen patients discussing the dangers around certain cancer meds that are sometimes used to treat mast cell disease. In particular, I have seen comments that newer targeted therapies “do not kill cells”, “cannot cause organ damage”, and are “harmless.” This is completely untrue. There are thousands of articles on the side effects and complications of all of the meds I have described here. None of them are harmless. Patients need to understand the risks associated with these therapies.
  • I would like to add a note about something sort of related. Xolair is an anti-IgE medication that is used by many mast cell patients. It is a subcutaneous injection and is administered in a healthcare setting. Patients are required to stay in the office for a little while after the shots are given to be sure that they don’t have a bad reaction. Because the patient is monitored in the office after the shot, the provider’s office will bill insurance for the observation period. The old billing code for this often comes up as “chemotherapy observation” because the same code was used for patients who needed monitoring after chemo. This means that patients may see “chemo” on the explanation of benefits from their insurance company. This does not mean that they received chemo. Xolair is NOT chemotherapy. It’s just a quirk of the medical billing. There is now a new code for post injection observation for meds that are not chemo but not everyone has caught up to it. Just figured I would mention this as people ask about it from time to time.

The MastAttack 107: The Layperson’s Guide to Understand Mast Cell Diseases, Part 27

35. Why are there different sets of criteria for mast cell activation syndrome? What are the differences between them?

To answer this fully, we need to first discuss the history behind some terms.

Mast cell activation syndrome was first used to describe episodes of mast cell mediator release symptoms in a paper published in 2007 (Akin 2007). Specifically, the term was used to detail the experience of patients who had symptoms we commonly associated with mast cell activation, like flushing, hives, and low blood pressure.

However, the patients in this study were all found to have some features of systemic mastocytosis. While they had some of the criteria for an SM diagnosis, they didn’t meet all the criteria. These patients sort of looked like SM and quacked like SM but would not cleanly meet the diagnostic criteria. So the author of that paper made a separate diagnostic category for them. He called it monoclonal mast cell activation syndrome.

The use of the word “monoclonal” is VERY important here. Monoclonal is a medical term that is associated with the body making too many cells at once so that the cells that are made don’t work correctly. Systemic mastocytosis is a condition in which the body makes too many cells at once that don’t work right. It is a monoclonal disorder. So the author of that paper in 2007 is linking monoclonal mast cell activation syndrome to systemic mastocytosis. He thought of it as sort of a “pre-SM” or “early SM”.

Shortly after that 2007 paper was released, another school of thought was proposed by different groups about the nature of mast cell activation syndrome. These groups also linked the term mast cell activation syndrome to symptoms of mast cell activation, like flushing, hives, and all the rest. However, they did NOT link mast cell activation syndrome to monoclonality. This means that these researchers felt that mast cell activation syndrome could be present without a condition where you make too many sloppy cells like systemic mastocytosis. So patients with no evidence of systemic mastocytosis could still have mast cell activation syndrome according to these groups. The two major groups that believed MCAS was distinct from SM were led by Afrin/Molderings and Castells.

Let’s recap:

In 2007, Akin described mast cell activation syndrome as something that happened only in patients that had some evidence of systemic mastocytosis but not enough to be diagnosed with systemic mastocytosis. In order for this group to diagnose you with mast cell activation syndrome, you had to have evidence of systemic mastocytosis. It was an add on diagnosis to SM, sort of like SM with really bad symptoms.

In the years that followed, two groups, led by Afrin/Molderings and Castells, described mast cell activation syndrome as something that was distinct from systemic mastocytosis and could be found in anyone, even if they had no evidence of systemic mastocytosis at all.

Okay. So these two groups agreed that MCAS could happen to anyone. But they differ greatly in how they think MCAS can be diagnosed. For these groups, MCAS is NOT an add on diagnosis to systemic mastocytosis. It is a standalone diagnosis and entity.

So if the term MCAS was already being used, why didn’t the other groups just call their diagnosis something different? There isn’t a good answer to this but it is super common. Things are much more fluidly changing in the time between coining a term and having the diagnosis accepted by a large organization like the CDC so that your insurance can bill for treatment for that diagnosis. It would be great if everyone just used different names for their variants but this just doesn’t always happen.

Castells feels that in order to be diagnosed with MCAS, you have to show mast cell mediator symptoms, response to medications to treat mast cell activation, and evidence of mast cell activation. You also have to rule out every other possible cause of mast cell activation. Keep in mind that your mast cells are normally activated for lots of reasons so this can really difficult to do.

Additionally, this school considers mast cell activation to be evidenced only by elevation of serum tryptase, 24 hour urinary n-methylhistamine or 24 hour urinary prostaglandin D2 or 9a,11b-prostaglandin F2. So if none of these mediators are high, the patient doesn’t meet the criteria for diagnosis.

Afrin’s criteria are harder to explain because he believes that you should provisionally be diagnosed with mast cell activation disease, which can be a few different things, and then it should be narrowed down to mast cell activation syndrome or another mast cell condition.

The key difference between Afrin’s criteria and Castells’ are that he accepts elevated levels of several other mast cell chemicals to prove mast cell activation. Afrin counts toward diagnosis elevation of serum tryptase, 24 hour urinary n-methylhistamine, serum or 24 hour urinary prostaglandin D2 or 9a,11b-prostaglandin F2, 24 hour urinary leukotriene E4, heparin in blood, and chromogranin A in blood. All of these are released by mast cells. But some of them are released by other cells too so it’s not as easy to say for sure that mast cells cause the elevations. Additionally, some of these mediators are REALLY difficult to measure accurately, like heparin. So some people feel that these tests are less reliable to indicate mast cell activation alone.

Let’s talk about puppies for a second because when things get tough, just find a puppy and things will be cool from there on out.

Let’s present these three schools of thought on MCAS as puppies.

Let’s say that Akin is saying that all dogs with 10 spots on them have SM. He’s saying that dogs with some spots, but less than 10, have MCAS. He is also saying that dogs with NO spots CANNOT have MCAS.

Castells is saying that it doesn’t matter how many spots the dog has but it has to have either blue or green eyes to have MCAS. She doesn’t think the MCAS is related to spots but that it is related to specific eye color.

Afrin is saying that it doesn’t matter how many spots the dog has, or what color eyes. He will accept eyes of many other colors if the dog has a lot of symptoms that look like mast cell activation or respond to medications to treat mast cell activation.

I have simplified this as much as possible so it’s easier to understand. For that reason, I have omitted a lot of things. I am in no way saying that what I described here represents everyone’s experience. I am not saying that at all.

If you want my opinion on what MCAS is, and I’m inclined to think you do because you’re on my website reading my thoughts about mast cell disease, I feel that the evidence points strongly towards a space that blends both Afrin’s and Castells’ points. I feel that we should use more mast cell mediators than just serum tryptase, 24 hour urinary n-methylhistamine, serum or 24 hour urinary prostaglandin D2 or 9a,11b-prostaglandin F2. But I personally find the reliability of tests for heparin level to be very problematic and elevations of chromogranin A can be from so many things. I am not AT ALL saying that people diagnosed with these elevated markers do not have MCAS. I professionally develop diagnostics and these tests are just not great.

I also don’t think there’s enough evidence yet to say that mast cell disease can be proven with a biopsy demonstrating a certain number of mast cells per hpf (high powered field, this is a measurement we use for counting things we see under a microscope). I think it is very suggestive of inflammation and mast cell activity. But there are MANY instances in which normal, healthy, asymptomatic patients have a bunch of mast cells/hpf in their biopsies when they are used in studies.

So I’m solidly in the MCAS is its own entity group but don’t fall evenly into one group or the other regarding diagnosis.

Regarding treatment, I land more squarely with Afrin. I believe that if you have tried all of the conventional treatments and continue to have life threatening episodes, you should be able to try more drastic treatments provided you are well supervised by a knowledgeable provider. This is my personal opinion and in no way reflects the views of my employer. I think that if you are constantly anaphylaxing, or have no safe foods, or have dystonic seizures, or can’t stand up, and you have gone through a long list of “reasonable treatments” that you have a right to try to preserve your life and the quality thereof with any means available.

So, yea. MCAS is a can of worms. But we owe it to MCAS patients to have these awkward discussions even though it’s, well, awkward. Patients are falling through the cracks and we owe it to them to identify what criteria would let us catch them so they can get diagnosed and treated sooner.

I’ve tried hard to explain this objectively but if I haven’t done great, let me know in the comments.

For more detailed reading, please visit these posts:
The Provider Primer Series: Mast cell activation syndrome (MCAS)
MCAS: Differing criteria among experts

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 14

I have answered the 107 questions I have been asked most in the last four years. No jargon. No terminology. Just answers.

22. Is MCAS an early form of SM?

• MCAS is not viewed as an early form of SM but the diagnosis of MCAS may precede a later diagnosis of SM.
• In the last few years, we have learned a lot about the genetics associated with mast cell diseases and how it occurs in families. As a result, we are beginning to understand that mast cell diseases occur more along a spectrum than as distinct categories. This means that there is a lot of overlap between conditions.
• While it is certainly not a new disorder, MCAS is a pretty recent diagnostic entity. The last decade has seen a large increase in diagnosis as it has been more frequently described. Because of how new it is, and also the fact that there aren’t uniform criteria for what MCAS is, there will be a level of uncertainty about how this disease tends to progress for some time.
• That uncertainty aside, we know that at least some patients with a long history of MCAS have continued to have symptoms without developing markers of systemic mastocytosis.
• However, some patients with history of MCAS do develop markers of systemic mastocytosis.
• Many patients do not receive bone marrow biopsies when they are diagnosed with MCAS because there is not always a reason to have one. It often doesn’t affect treatment. If there is no sign of organ damage, the patient has a negative blood test for the CKIT D816V mutation, and their baseline tryptase is below 20 ng/mL, most doctors do not order a bone marrow biopsy. This means that some patients who are diagnosed with MCAS may have had SM all along but it wasn’t found until a biopsy was performed later.
• In 2007, monoclonal mast cell activation syndrome was described in scientific literature. This condition is diagnosed when a patient meets some criteria of systemic mastocytosis but not enough for a diagnosis of SM.
• Monoclonal mast cell activation syndrome is more often viewed as a “pre-SM”. I personally view it this way. Before it had a name, researchers called it “pre-diagnostic SM.” Literally, SM before they could diagnose it as SM.

For more detailed reading, please visit these posts:

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

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

The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (SM-AHD, MCL, MCS)

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, part 7

I have answered the 107 questions I have been asked most in the last four years. No jargon. No terminology. Just answers.

 

13. What do these biopsy tests look for?
• They look for the shape, quantity, and distribution of mast cells.
• They also look for specific proteins on the outside of mast cells and tissue damage around mast cells.
• Systemic mastocytosis and cutaneous mastocytosis are generally diagnosed by biopsy. With very, very few exceptions, you cannot meet the criteria for systemic mastocytosis without having a positive biopsy. Sometimes people with monoclonal mast cell activation syndrome are diagnosed by having a biopsy that looks like a very early phase of systemic mastocytosis.
• The diagnostic criteria for mast cell activation syndrome are hotly contested. Most doctors do not use biopsies to diagnose MCAS because there are not uniform criteria. Some doctors feel that more than 20 mast cells in a field when you look through the microscope is a sign of MCAS.
• Cutaneous mastocytosis is having too many broken mast cells in your skin. For this condition, they are looking for either 20 mast cells to be present in the microscope field (hpf) when looking at the skin, or for there to be at least one cluster of at least fifteen mast cells.
• Clustering is a very important feature of mastocytosis. When mast cells bunch together in a cluster, it is easier to damage the tissue. They are essentially punching holes in the tissue by clustering.
• Systemic mastocytosis is having too many broken mast cells made by the bone marrow. Systemic mastocytosis is usually diagnosed by a positive bone marrow biopsy. However, sometimes people are diagnosed by biopsies of other organs. Skin biopsy is NOT enough to diagnose systemic mastocytosis.
• For systemic mastocytosis, there are three key things they are looking for in the biopsy.
• They are looking for at least one cluster of at least fifteen mast cells.
• They are looking for some of the mast cells to be shaped like spindles, sort of smushed at the ends and round in the middle. You see this shape a lot when cells are trying to stick together in a cluster.
• They are looking for special proteins that are only found when a patient has systemic mastocytosis or monoclonal mast cell activation syndrome. They are called CD25 and CD2. These are like flags that the mast cells fly to tell us they are broken. One of them, CD25, actually helps mast cells cluster together.
• In biopsies, they usually also look for the protein CD117. This is a normal flag for mast cells to fly and just allows us to know that we are looking at mast cells.

For more detailed reading, please visit these posts:

The Provider Primer Series: Management of mast cell mediator symptoms and release

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

The Provider Primer Series: Cutaneous Mastocytosis/ Mastocytosis in the Skin

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

The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (SM-AHD, MCL, MCS)

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 5

I have answered the 107 questions I have been asked most in the last four years. No jargon. No terminology. Just answers.

10. How is mast cell disease diagnosed?
• There are several tests you need to definitively determine if you have mast cell disease and what kind you have.
• The most well known test for mast cell disease is serum tryptase. This is a blood test. This is the test doctors are most likely to have heard of. Doctors may think that you can’t have mast cell disease if tryptase is normal. This is not true.
• If a patient has a tryptase over 20 ng/mL, the next step is usually a bone marrow biopsy. A tryptase over 20 ng/mL increases the likelihood that a patient has systemic mastocytosis. SM is most commonly confirmed by a bone marrow biopsy.
• You need a special stain in order to see mast cells in any biopsy. Stains that show mast cells include Giemsa Wright stain and toluidine blue. Your doctor should specify these stains.
• Several tests must be run on the bone marrow biopsy to look for clonal mast cell disease. Remember that in clonal diseases, the body makes too many broken cells.
• The shape of the mast cells in the biopsy is very important. If the mast cells are not shaped right, this can be a sign of mast cell disease.
• The number of mast cells grouped together in the body is also important. If 15 or more mast cells are all stuck together, this is called a cluster. When mast cells are clustered together like this, they can punch holes in the tissue and damage it a lot. This prevents the tissue from working right.
• Immunohistochemistry (IHC) is a way to find specific proteins that allow us to know what cells we are looking at in the biopsy. Often, these proteins are on the outside of the cells. Think of these are flags that a cell can wave. IHC can look for the specific flags a cell is waving so that we know for sure which cell is which. For mast cell disease, they want to look for CD117, CD25, and CD2. The CD117 flag is flown normally by all mast cells. CD25 and CD2 are special flags flown by mast cells if you have clonal mast cell disease.
• PCR is a way to look for genetic mutations. They need to look for a mutation in the mast cells in the bone marrow. The mutation is found at a specific place in the CKIT gene. This mutation is found in 80-90% of patients with systemic mastocytosis. It may also be found if patients have monoclonal mast cell activation syndrome.
• If a patient does not have a tryptase over 20 ng/mL, a bone marrow biopsy is often not ordered. There are other tests that can indicate mast cell disease.
• Urine collected over 24 hours can be tested for specific chemicals. In the case of mast cell disease, they are looking for chemicals that can be high if you have mast cell disease. These chemicals have very long, complicated names. I will explain in a later post exactly what they are and what they do. The most common ones are called n-methylhistamine, prostaglandin D2, 9a,11b-prostaglandin F2, and leukotriene E4. Anti-heparin Xa and chromogranin A are sometimes tested. They are much less reliable as indicators of mast cell disease than the others mentioned here.
• If a patient is suspected to have cutaneous mastocytosis, a skin biopsy is needed to confirm. As with bone marrow biopsies, your doctor should specify that they need to use toluidine blue or Giemsa Wright stain to be sure they see the mast cells.
• The skin biopsy should also receive the other tests I described above for bone marrow biopsy: the counting of mast cells and looking at the shape; looking for CD117, CD2, and CD25; and looking for the same mutation with PCR.
11. What kind of doctor diagnoses mast cell disease? Can any doctor order these tests?
• Doctors from all different specialties may diagnose and manage mast cell disease. It depends upon the individual provider and where you are located. It could be a dermatologist, allergist, hematologist, pulmonologist, gastroenterologist, or another specialist.
• The serum tryptase is the easier to order and the most well known test. Many labs can run this test.
• The 24 hour urine tests are specialized. Some of them are run in only a few places and samples are usually shipped there. Most often, these samples are run at the Mayo Clinic. Many outpatient labs have no way to run those tests. You will need to speak with your doctor about how to get these tests. It is often easiest if they are run by a hospital lab but again, this depends upon the hospital.
• The PCR genetic test for this specific gene is run in more places than the urine tests but is still not very common. Again, it is often easiest if they are run by a hospital lab.
• A bone marrow biopsy is usually ordered by a hematologist or by another specialist that works commonly with hematologists. They are usually performed by hematology providers. Some testing can usually be performed in house (the counting of the cells and looking at the shape) while others may need to be sent out (the IHC testing).
• A skin biopsy is usually ordered by a dermatologist. Some testing can usually be performed in house (the counting of the cells and looking at the shape) while others may need to be sent out (the IHC testing).
For more detailed reading, please visit these posts:

The Provider Primer Series: Management of mast cell mediator symptoms and release

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

The Provider Primer Series: Cutaneous Mastocytosis/ Mastocytosis in the Skin

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

The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (SM-AHD, MCL, MCS)

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 2

I have answered the 107 questions I have been asked most in the last four years. No jargon. No terminology. Just answers.

3. What causes mast cell disease?

  • The cause of mast cell disease is not yet definitively known.
  • As mentioned yesterday, when the body makes too many copies of a broken cell, those cells are called ‘clonal’ cells. In clonal forms of mast cell disease, the bone marrow makes too many mast cells. Those mast cells also don’t work correctly. Examples of clonal mast cell diseases are systemic mastocytosis and cutaneous mastocytosis.
  • Patients with systemic mastocytosis often have a specific genetic mutation called the CKIT D816V mutation. About 80-90% of systemic mastocytosis patients have this mutation. This mutation is in mast cells and it tells the mast cells to stay alive WAY longer than they should. And mast cells already live for months or years, a very long time for cells to live in the body. So patients with this mutation can end up with way too many broken mast cells.
  • Despite the fact that we know that many patients have this mutation, we do not say that this mutation CAUSES the disease. The reason for this is that sometimes, mast cell patients don’t have the mutation when they get sick but they develop it later. Sometimes, mast cell patients have the mutation and then lose it later. So we are still looking for something that causes the disease.
  • Patients with non-clonal mast cell disease do not have a single major mutation like the CKIT D816V mutation. This makes it harder to diagnose. Researchers have found that many times, patients with MCAS DO have mutations similar to the ones systemic mastocytosis patients do. But the MCAS patients often have different mutations from each other. That’s why it’s not helpful yet for diagnosis.
  • Despite the fact that the mutations described here are not considered to be heritable, there is more and more evidence that mast cell disease can happen to many people in the same family. See the next question for more details.

4. Is mast cell disease heritable?

  • Mast cell disease often affects multiple members of the same family. Importantly, patients often have a different type of mast cell disease than their relatives. This implies that mast cell disease is more of a spectrum rather than several different diseases.
  • A survey found that 74% of mast cell patients interviewed reported at least one first degree relative that had mast cell disease. This same study found that 46% of those patients had mast cell disease that affected more than just their skin. This is called systemic disease.
  • The CKIT D816V mutation is the mutation most strongly associated with clonal mast cell disease. The CKIT D816V mutation is NOT heritable.
  • There are very rare instances of other heritable mutations in families that have mast cell disease. The significance of this is not clear.

5. Can mast cell disease be cured?

  • Generally speaking, there is no cure for mast cell disease.
  • Children who present with cutaneous mastocytosis sometimes grow out of their disease. Their lesions disappear. Their mast cell symptoms affecting the rest of the body may disappear. We do not know why this happens. It has been heavily researched with long term follow up of children with childhood mastocytosis (at least one paper followed them for 20 years).
  • Children with true systemic mastocytosis do not grow out of their disease.
  • There is not yet data on children with MCAS. Anecdotally, they do not seem to grow out of their disease like kids with cutaneous mastocytosis can. Importantly, this is just what it looks like to me. Again, there is no data.
  • People with adult onset mast cell disease have lifelong disease.
  • There is one notable exception to this scenario. There are reports of curing mast cell disease following hematopoietic stem cell transplant/bone marrow transplant.
  • Transplantation is EXTREMELY dangerous. The transplant is MUCH, MUCH more dangerous than mast cell disease. Many people do not survive the protocol necessary to prepare for transplant. Many die from complications, or from a disease they acquired after their transplant.
  • Rarely, people may have malignant forms of mast cell disease, aggressive systemic mastocytosis (ASM) or mast cell leukemia (MCL). A few patients with these diseases have tried transplants after everything else failed. While some did see improvement after transplant, no one has survived more than a few years.
  • Conversely, sometimes people with mast cell disease have these transplants for other reasons, like having another blood cancer or bone marrow disease that requires transplant. In this group of people, some see drastic improvement of their mast cell disease. Some see a full remission of mast cell disease. Some do not get any improvement. These findings are pretty recent so it’s hard to be more specific.

For more detailed reading, please visit these posts:

The Provider Primer Series: Introduction to Mast Cells

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

The Provider Primer Series: Cutaneous Mastocytosis/ Mastocytosis in the Skin

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

The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (SM-AHD, MCL, MCS)

Mast cell disease in families

Heritable mutations in mastocytosis

The MastAttack 107: The Layperson’s Guide to Understanding Mast Cell Diseases, Part 1

I have answered the 107 questions I have been asked most in the last four years. No jargon. No terminology. Just answers.

  1. What are mast cells?
    • Mast cells are white blood cells that live in tissues. It is a little misleading that mast cells are white blood cells because they don’t live in the blood. Mast cells are born in the bone marrow, the squishy tissue inside bones where blood cells are made. From the bone marrow, they are sent to the blood stream. Mast cells use the bloodstream to carry them to their final destination so they do not stay in the blood for very long. Mast cells move out of the blood stream and into tissues throughout the body. Mast cells live for months or years, a long time for cells to live in the human body.
    • Mast cells do many things in the body. They are largely responsible for allergic reactions and anaphylaxis. They have many other jobs, like healing wounds, regulating reproductive activities (menstruation, pregnancy), and fighting infections from viruses, bacteria, fungi, and even intestinal parasites like worms. The original function of mast cells thousands of years ago was probably to fight off intestinal parasites. Mast cells are found in many tissues and are essential for correct functioning of the body.
    • Mast cells have many pouches inside of them called granules. These granules hold chemicals made by the mast cells. These chemicals help the mast cells to do their various jobs. They also help mast cells to communicate with other cells nearby or in other parts of the body. These chemicals can be released into the bloodstream to signal for other immune cells to come to the mast cell that released them.
  2. What is mast cell disease?
    • Mast cell diseases are rare diseases in which your body makes too many mast cells and/or mast cells do not function correctly. In the US, diseases that affect fewer than 200,000 people are called rare diseases.
    • Mast cell diseases are broadly classified into two groups: clonal and non-clonal (also called proliferative and non-proliferative).
    • When the body makes too many copies of a broken cell, those cells are called ‘clonal’ cells. In clonal forms of mast cell disease, the bone marrow makes too many mast cells. Those mast cells also don’t work correctly. They use too much energy on the wrong things. Because these mast cells are often busy making truble, they don’t have as much energy to do their normal necessary functions.
    • Clonal mast cell diseases include all forms of systemic mastocytosis (indolent, smoldering, aggressive, and mast cell leukemia); all forms of cutaneous mastocytosis (urticaria pigmentosa, of which telangiectasia macularis eruptiva perstans is a subtype, diffuse cutaneous mastocytosis); mastocytoma (usually found on the skin but also found elsewhere); mast cell sarcoma; and monoclonal mast cell activation syndrome. Importantly, in clonal mast cell diseases, the problem is not just that too many mast cells are made – those mast cells must also be dysfunctional for the disease to be clonal.
    • In non-clonal mast cell disease, the number of mast cells may be normal, but the cells are broken. Importantly, people with non-clonal mast cell disease may make more mast cells than normal, but not enough to be considered a clonal disease. In these diseases, even if the bone marrow makes the normal amount of mast cells, they still do not work correctly. They use too much energy on the wrong things. Because these mast cells are often working to inflame the body when it is not needed, they don’t have as much energy to do their normal necessary functions.
    • Non-clonal mast cell diseases include all other forms of mast cell disease: mast cell activation syndrome (secondary and idiopathic); familial hypertryptasemia; and mastocytic enterocolitis, which is recognized by some groups as its own disease, and by other groups as part of different mast cell diseases.
    • In these diseases, mast cells do not function properly. In all mast cell diseases, mast cells can get irritated easily. They respond to things in the environment and inside the body that they think are dangerous, even when those things are normal and safe for most people. This response is called mast cell activation.
    • Mast cell activation causes many symptoms. Many of these symptoms are “allergic” in nature. Some are not directly recognizable as “allergic”. Symptoms can affect every bodily system or may be localized to only one or two. It differs from person to person and can change over time within a person. You cannot know which mast cell disease a person has based upon their symptoms.

For more detailed reading, please visit these posts:

The Provider Primer Series: Introduction to Mast Cells

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

The Provider Primer Series: Cutaneous Mastocytosis/ Mastocytosis in the Skin

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

The Provider Primer Series: Diagnosis and natural history of systemic mastocytosis (SM-AHD, MCL, MCS)

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

In 2009, Walker and colleagues published a paper called “Duodenal mastocytosis, eosinophilia and intraepithelial lymphocytosis as possible disease markers in the irritable bowel syndrome and functional dyspepsia.”  The term “mastocytosis” as used here is not equivalent the term “mastocytosis” as in cutaneous mastocytosis or systemic mastocytosis. It is one of several papers to do so and has generated a lot of confusion as a result.

The suffix –osis is commonly used in medical terminology.  It means increase or production of something, but it also connotes that this increase results from a disease process.  Here, the author means not that these patients meet the criteria for systemic mastocytosis, which we know to be a neoplastic disease originating in the bone marrow, but that there are more mast cells than expected in these biopsies.

Excessive production of mast cells in an organ that is not the skin is the defining feature of systemic mastocytosis.  SM patients show some combination of the following characteristics: infiltration of tissue with mast cells clustered together; expression of receptors CD25 and/or CD2 on the mast cells; spindle shaped mast cells; presence of the CKIT D816V mutation; and  baseline tryptase over 20 ng/ml.  When a patient shows too many mast cells without having any of these markers, it is not called mastocytosis.  It is called mast cell hyperplasia.

Consider the following two scenarios:

Let’s imagine that you are a house builder.  For many years, you only build houses when people call your boss and say they need a house.  After your boss gets the call, she calls you to tell you to build a house for these people in the location they have requested.  Sometimes more people need houses than others, so at times you make more, and other times, you make less.  You never build houses unless your boss tells you to and you are able to build them correctly due to having the correct time and resources.  You may think that your boss is telling you to build too many houses sometimes but it is always because she is getting lots of requests from customers to build houses.

In this scenario, mast cells are house builders. They only make new mast cells when they receive appropriate signals from the body.  Sometimes your body makes more mast cells, like to fight an infection or when you have an allergic response.  But the mast cells ALWAYS wait for the correct signal from the body to make more cells.  They do not decide to make too many cells on their own.

Now let’s imagine that after years of being a house builder, you wake up one day with a compulsion to see how fast you can build a house.  Your boss calls you and says she needs one house, so you build that house and then you build four more at the same time.  Instead of building carefully one at a time, you are building five houses at the same time.  This means the houses are not built correctly.  You call your boss to say you are done with the five houses and your boss gets mad.  Where are we going to put these extra four houses?  She decides to move those four houses to another town that doesn’t have too many houses yet.  She tells you not to make too many houses again.

But you just cannot stop making houses.  Making houses is the best!  Who cares if there are little mistakes?  People can still live in them safely.  You wake up every day with a fervent need to build houses.  Your friends and family are concerned about you and stage an intervention.  You will not be moved.  You are building tons of houses at once now.  Your boss is calling you screaming at you to stop making houses because they are defective and she doesn’t have anywhere to put them.  She has been sending them to places that already have too many houses so it is getting really crowded and people are complaining.  You stop answering your boss’s calls.  These people don’t understand the importance of building houses.  No matter what anyone says to you, you will not stop making houses and they cannot make you stop.

In this scenario, the problem isn’t that the boss is telling the builder to make too many houses.  The problem here is that the builder is ignoring all the signals to stop.  This scenario represents systemic mastocytosis.  The mast cells here are making too many mast cells for the wrong reasons and they don’t work right.

I want to be very clear about something – the fact that a person has a lot of mast cells per hpf but doesn’t have markers for SM does NOT mean that these people are not suffering.  Regardless of how the mast cells ended up there in excessive populations, they will cause large scale inflammation and GI symptoms.  Nor am I saying that phenomena like mastocytosis enterocolitis or allergic mastocytic enterocolitis are definitely not mast cell diseases – it is possible that the mast cells in those cases demonstrate markers we have not yet found or that there is an error in the cells that become mast cells.  I am just describing the way these two categories are distinguished from one another at this time.  It is not my intention to disenfranchise anyone.  We are all united in the suckage that is GI symptoms as a result of mast cells.

How do you tell the difference between systemic mastocytosis and mast cell hyperplasia?  That is the purpose of the SM diagnostic criteria.  As I said before, you need to meet one major and one minor criterion, or three minor criteria, from the WHO Systemic mastocytosis criteria.  If you meet some of the criteria, but not enough for SM, that is still evidence of a clonal, proliferative mast cell disease.  This means that it is still evident that too many mast cells are being made despite signals to stop.  The state of meeting some criteria for SM but not enough for an SM diagnosis is called monoclonal mast cell activation syndrome (MMAS). This topic will be covered in detail in a later post in this series.

Many diseases involve mast cells, including various cancers and autoimmune diseases, among others. So why aren’t they considered mast cell diseases like systemic mastocytosis and mast cell activation syndrome? These are not mast cell diseases because in these situations, mast cells are getting signals to make too many mast cells and to cause inflammation.  They are the house builder when the boss is telling them to make more houses than usual, but the boss is doing that because customers need those houses.  Mast cell diseases are the house builder that has a compulsion to build houses even when they aren’t needed and everyone is telling them to stop.

Remember this distinction when you are reviewing papers and pathology reports.  The word mastocytosis is often used when they really mean mast cell hyperplasia.  Mastocytosis in proper usage means too many mast cells because the mast cells are defective.  Mast cell hyperplasia means too many mast cells because the mast cells are receiving inflammatory signals from elsewhere.

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

Let’s have a chat about the idea that 20 mast cells/hpf (high powered field) in gastrointestinal biopsy is higher than normal.

First, let’s review a few things.

The WHO diagnostic criteria for systemic mastocytosis are as follows:

Table 1: World Health Organization Criteria for Systemic Mastocytosis (2008)
  • Systemic mastocytosis is diagnosed in the presence of: 1 major and 1 minor criterion; or 3 minor criteria.
  • Biopsy specimens can be from any non-cutaneous organ (any organ that is not the skin).
Major criterion:
Multifocal, dense aggregates of mast cells (15 or more) detected in sections of bone marrow and confirmed by tryptase immunohistochemistry or other special stains:
Minor criterion:
1.       In biopsy section, more than 25% of mast cells in the infiltrate have atypical morphology, or, of all the mast cells in the smear, more than 25% are immature or atypical. (25% of the mast cells are shaped wrong.)
2.       Mast cells co-express CD117 with CD25 and/or CD2. (Mast cells show markers CD25 or CD2 on their outsides.)
3.       Detection of KIT point mutation at codon 816 in bone marrow, blood or other extracutaneous organs. (Positive for the CKIT D816V mutation.)
4.       Serum total tryptase persistently >20 ng/ml (not a valid criteria in cases of systemic mastocytosis with associated clonal non-hematologic mast-cell lineage disease). (Baseline serum tryptase over 20 ng/ml – baseline, not reaction.)

 

There are several different diagnostic algorithms floating around for mast cell activation syndrome (MCAS).  They are summarized here:

Table 2: Diagnostic algorithms for  mast cell activation syndrome (MCAS, also called mast cell activation disorder, MCAD)
  • Biopsy specimens can be from any non-cutaneous organ (any organ that is not the skin).
Molderings, Afrin 2011 Akin, Valent, Metcalfe 2010 Valent, Akin, Castells, Escribano, Metcalfe et al 2012
MCAD (mast cell activation disease, an  umbrella term including both MCAS and SM) is diagnosed if both major criteria, or one major criterion and one minor criterion, are present; following bone marrow biopsy, diagnosis is narrowed down to either SM or MCAS MCAS diagnosed if all criteria are met MCAS diagnosed if all criteria are met
Major Criteria
Multifocal of disseminated dense infiltrates of mast cells in bone marrow biopsies and/or in sections of other extracutaneous organ(s) (GI tract biopsies; CD117-, tryptase- and CD25- stained) Episodic symptoms consistent with mast cell mediator release affecting ≥2 organ systems evidenced as follows:

  • Skin: urticaria, angioedema, flushing
  • Gastrointestinal: nausea, vomiting, diarrhea, abdominal cramping
  • Cardiovascular: hypotensive syncope or near syncope, tachycardia
  • Respiratory: wheezing
  • Naso-ocular: conjunctival injection, pruritus, nasal stuffiness
 Typical clinical symptoms
Unique constellation of clinical complaints as a result of a pathologically increased mast cell activity (mast cell mediator release symptom) A decrease in the frequency or severity or resolution of symptoms with antimediator therapy: H1– and H2-histamine receptor inverse agonists, antileukotriene medications (cysteinyl leukotriene receptor blockers or 5-lipoxygenase inhibitor), or mast cell stabilizers (cromolyn sodium) Increase in serum total tryptase by at least 20% above baseline plus 2 ng/ml during or within 4 h after a symptomatic period
  Evidence of an increase in a validated urinary or serum marker of mast cell activation: documentation of an increase of the marker to greater than the patient’s baseline value during a symptomatic period on ≥2 occasions or, if baseline tryptase levels are persistently >15 ng, documentation of an increase of the tryptase level above baseline value on 1 occasion. Total serum tryptase level is recommended as the marker of choice; less specific (also from basophils) are 24-hour urine histamine metabolites or PGD2 or its metabolite 11-β-prostaglandin F2. Response of clinical symptoms to histamine receptor blockers or MC-targeting agents e.g. cromolyn
  Rule out primary and secondary causes of mast cell activation and well-defined clinical idiopathic entities
Minor Criteria
Mast cells in bone marrow or other extracutaneous organ(s) show an abnormal morphology (>25%) in bone marrow smears or in histologies
Mast cells in bone marrow express CD2 and/or CD25
Detection of genetic changes in mast cells from blood, bone marrow or extracutaneous organs for which an impact on the state of activity of affected mast cells in terms of an increased activity has been proved
Evidence of a pathologically increased release of mast cell mediators by determination of the content of:

  • Tryptase in blood
  • N-methylhistamine in urine
  • Heparin in blood
  • Chromogranin A in blood
  • Other mast cell specific mediators (leukotrienes, PGD2)

 

Additionally, a questionnaire (found here: http://www.wjgnet.com/2218-6204/abstract/v3/i1/1.htm) designed to assess the likelihood of mast cell activation disease (MCAS or SM) in a patient was published in 2014 by Lawrence Afrin.  It assigns numerical values to various findings, such as mediator elevation, symptoms, clinical findings, and biopsy features.

The criteria for systemic mastocytosis can be met with a gastrointestinal biopsy showing the features listed above in Table 1.  So if you have gastrointestinal scopes and your biopsy shows mast cells with the features listed in Table 1, then that contributes to receiving a diagnosis of SM.  If you meet some of the criteria but not all of them, with a GI biopsy or otherwise, then you receive a diagnosis of monoclonal mast cell activation syndrome (MMAS), which is like a pre-SM.

A common adage in the mast cell community is that having 20 or more mast cells in a high powered field (hpf, what you see when you look through a microscope with high magnification) is diagnostic for mast cell activation syndrome.

In 2006, a paper was published called “Mastocytic enterocolitis: Increased mucosal mast cells in chronic intractable diarrhea.” This paper detailed a study that quantified the mast cells in biopsies of duodenum (small intestine) and colon in patients with chronic diarrhea that resisted treatment. These counts were then compared to patients who had other conditions that caused chronic diarrhea, and to some control subjects that had no GI symptoms.

Table 3: Average mast cell count per hpf in colon and duodenum (Jakate 2006)
Group Average mast cell count in colon and duodenum
Healthy control group 13.3 ± 3.5
Inflammatory GI disease control group 12.4 ± 2.3
Intractible chronic diarrhea group 25.7 ± 4.5

 

The average mast cell count in the healthy control group was 13.3/hpf.  (See Table 3 for details.) Two standard deviations from this value is approximately 20/hpf.  Two standard deviations (SD) is a statistical mechanism that allows for variation in the patient, sample or test procedure.  It is common to round to an even number.

The patients in this group were not evaluated for typical mast cell symptoms.  No information is provided regarding history of allergic or atopic disease. This paper is the origin of the idea that more than 20 mast cells/hpf in the gastrointestinal tract is considered higher than normal.

 

References:

Jakate S, et al. Mastocytic enterocolitis: Increased mucosal mast cells in chronic intractable diarrhea.  Arch Pathol Lab Med 2006; 130 (3): 362-367.

Akhavein AM, et al. Allergic mastocytic gastroenteritis and colitis: An unexplained etiology in chronic abdominal pain and gastrointestinal dysmotility. Gastroenterology Research and Practice (2012): Article ID 950582.

Martinez C, et al. Diarrhoea-predominant irritable bowel syndrome: an organic disorder with structural abnormalities in the jejunal epithelial barrier. Gut 2013; 62: 1160-1168,

Sethi A, et al. Performing colonic mast cell counts in patients with chronic diarrhea of unknown etiology has limited diagnostic use. Arch Pathol Lab Med 2015; 139 (2): 225-232.

Doyle LA, et al. A clinicopathologic study of 24 cases of systemic mastocytosis involving the gastrointestinal tract and assessment of mucosal mast cell density in irritable bowel syndrome and asymptomatic patients. Am J Surg Pathol 2014; 38 (6): 832-843.

Ramsay DB, et al. Mast cells in gastrointestinal disease. Gastroenterology & Hepatology 2010; 6 (12): 772-777.

Zare-Mirzaie A, et al. Analysis of colonic mucosa mast cell count in patients with chronic diarrhea. Saudi J Gatroenterol 2012; 18 (5): 322-326.

Walker MM, et al. Duodenal mastocytosis, eosinophilia and intraepithelial lymphocytosis as possible disease markers in the irritable bowel syndrome and functional dyspepsia. Aliment Pharmacol Ther 2009; 29 (7): 765-773.

Hahn HP, Hornick JL. Immunoreactivity for CD25 in Gastrointestinal Mucosal Mast Cells is Specific for Systemic Mastocytosis. American Journal of Surgical Pathology 2007; 31(11): 1669-1676.

Vivinus-Nebot M, et al. Functional bowel symptoms in quiescent inflammatory bowel diseases : role of epithelial barrier disruption and low-grade inflammation. Gut 2014; 63: 744-752.

Minnei F, et al. Chronic urticaria is associated with mast cell infiltration in the gastroduodenal mucosa. Virchows Arch 2006; 448(3): 262-8.

Hamilton MJ, et al. Mast cell activation syndrome: A newly recognized disorder with systemic clinical manifestations. J Allergy Clin Immunol 2011; 128: 147-152.

Barbara G, et al. Activated mast cells in proximity to colonic nerves correlate with abdominal pain in irritable bowel syndrome. Gastroenterology 2004; 126(3): 693-702.

Guilarte M, et al. Diarrhoea-predominant IBS patients show mast cell activation and hyperplasia in the jejunum. Gut 2007; 56: 203-209.

Dunlop SP, et al.  Age related decline in rectal mucosal lymphocytes and mast cells. European Journal of Gastroenterology and Hepatology 2004; 16(10): 1011-1015.

Afrin LB, Molderings GJ. A concise, practical guide to diagnostic assessment for mast cell activation disease. World J Hematol 2014; 3 (1): 1-17.

Molderings GJ, et al. Mast cell activation disease: a concise, practical guide to diagnostic workup and therapeutic options. J Hematol Oncol 2011; 4 (10).

Akin C, et al. Mast cell activation syndrome: proposed diagnostic criteria. J Allergy Clin Immunol 2010; 126 (6): 1099-1104.

Valent P, et al. Definitions, criteria and global classification of mast cell disorders with special reference to mast cell activation syndromes: a consensus proposal. Int Arch Allergy Immunol 2012: 157 (3): 215-225.

 

 

 

MCAD, MCAS and the hierarchy of mast cell disease classifications

I have seen several posts recently expressing confusion about various mast cell diagnoses so I figured I would put up a post to clear things up.
Mast cell activation disorder (MCAD) is a catch-all term for mast cell disease (MCD.)  MCAD and MCD can be used interchangeably.  So if you have any mast cell disease, you have MCAD.  If you have SM, you have MCAD, because SM is a type of MCAD.  If you have UP, you have MCAD, and so on.  MCAD is an umbrella term.  It is non-specific.  It is similar to being told that you have heart disease when you have mitral valve prolapse.  It is true, but it is not precise enough to give all information needed to treat effectively.
Mast cell activation syndrome (MCAS) is the diagnosis you get if you do not meet the criteria for any of the defined mast cell diseases, but have mast cell mediator related symptoms.  You cannot have MCAS and another mast cell disease because, by its definition, MCAS is ONLY diagnosed if you do NOT meet the criteria for any other mast cell disease.  You cannot have UP and MCAS.  You cannot have SM and MCAS.  I think some people think that MCAS means you have mediator related symptoms.  This is not the case.  You can have mediator related symptoms with pretty much any mast cell disease. 
A paper was published a few years ago by a doctor who considers mast cell activation symptoms to be due exclusively to proliferation (like in SM.)  He wrote a paper that says that MCAS is found in people with SM.  This paper sort of confused the issue for a lot of people.  However, the mast cell community (including researchers and prominent doctors) do not consider this to be the case.  They agree that you cannot have SM and MCAS.
Also confusing is the fact that mast cell activation (MCA) is NOT the same as MCAS.  MCA just means that your mast cells are activated, which occurs in any mast cell disease.  MCA is not a diagnosis, it is a symptom.  So you can have MCA in SM.  But you still can’t have MCAS in SM.
So if you have SM and have lots of mediator related symptoms, you have SM.  If you want to speak broadly, you have SM.
If you test negative for SM and have no CM, but have mast cell symptoms and elevated mast cell markers, you have MCAS. 
If you have UP and then later develop SM, you have SM with skin involvement, or SM with UP. 
If you have UP or TMEP and have lots of mediator related systemic symptoms, you do NOT have UP and MCAS.  You have UP.  UP and TMEP (forms of CM) can cause systemic symptoms.  But you cannot have MCAS because you can only have MCAS if you do not meet the criteria for another mast cell disease.
Let’s review.
If you have UP: you have UP, you have CM, you have MCAD.
If you have TMEP: you have TMEP, you have CM, you have MCAD.
If you have SM: you have SM, you have MCAD.
If you have SM with UP: you have SM with skin involvement, you have UP, you have MCAD.
If you have SM with TMEP: you have SM with skin involvement, you have TMEP, you have MCAD.
If you have SM-AHNMD: you have SM-AHNMD, you have MCAD.
If you have ASM: you have ASM, you have MCAD.
If you have MCL: you have MCL, you have MCAD.

If you have MCAS: you have MCAD.

Reference:
Molderings GJ, Brettner S, Homann J, Afrin LB. Mast cell activation disease: a concise practical guide for diagnostic workup and therapeutic options. J. Hematol. Oncol.2011; 4:10-17.