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 8

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

14. Are there any special instructions for the tests to diagnose mast cell disease?
• There are a lot of tests used to diagnose mast cell disease. There are certainly people who slip through the cracks with the current diagnostic criteria.
• Remember this as you read the following: DO NOT, UNDER ANY CIRCUMSTANCES, EVER, DISCONTINUE MEDICATION FOR TESTING WITHOUT EXPLICIT INSTRUCTIONS TO DO FROM A DOCTOR THAT UNDERSTANDS MAST CELL DISEASE. Stopping medications for mast cell disease can be very dangerous.
• The biopsy forms the centerpiece of diagnosis of both cutaneous and systemic forms of mastocytosis.
You can increase your chance of positive skin biopsy by choosing either a permanent lesion or an area of skin that is frequently reactive.
• For internal organs, including bone marrow, you can’t always tell where to biopsy just by looking. The area may look normal but show inflammation when viewed with a microscope.
• If patients do not need to take daily corticosteroids because they do not make their own (adrenal insufficiency or Addison’s disease), they are often recommended to not use corticosteroids (prednisone or similar) for five days before a bone marrow biopsy. Taking corticosteroids can tell your body to make a lot of extra white blood cells which can make it harder to give a correct diagnosis.
• The CKIT D816V mutation test is often done on a blood sample. It is much more accurate when a bone marrow biopsy is tested because there are many more mast cells. Mast cells do not live in the blood so the blood test is less accurate. If the test is positive in blood, we assume that the patient is truly positive. If the test is negative in blood, we are not sure if the patient is truly negative.
• Serum tryptase is a test with a lot of caveats. It is influenced heavily by timing and patient factors like weight. Many people with mast cell disease have normal serum tryptase. It is good for tracking progression of disease in patients with systemic mastocytosis.
• About 85% of patients with systemic mastocytosis have a baseline tryptase value over 20 ng/mL. Patients with monoclonal mast cell activation syndrome may also have baseline tryptase value over 20 ng/mL. For these patients, they should have two different tests from days when they are not especially reactive, or have had anaphylaxis.
• For patients with mast cell activation syndrome, we are often looking for an increase in tryptase during a reaction or anaphylactic event. In these patients, experts recommend having blood drawn 15 minutes to 4 hours after onset of the event.
• Another sample should be drawn 1-2 days later so that you have a sample to compare with the tryptase level during the event. Many experts accept a level increased by 20% plus 2 ng/mL above the baseline to be indicative of mast cell activation. (I made a typo on this that said 20% to 2 – sorry!)
• As we have previously discussed, many mast cell mediators should be kept cold because they break down quickly. 24 hour urines for n-methylhistamine, prostaglandin D2, 9a,11b prostaglandin F2, and leukotriene E4 should be kept cold.
Performing a 24 hour urine when you are having a reaction event can increase the likelihood of mediator release.
COX inhibitors will interfere with prostaglandin production. Some patients stop these meds before giving 24 hour urines for prostaglandin testing. DO NOT STOP MEDS WITHOUT BEING ADVISED BY AN EXPERIENCED MAST CELL PROVIDER.
Lipoxygenase inhibitors will interfere with leukotriene production. Some patients stop these meds before giving 24 hour urines for leukotriene testing. DO NOT STOP MEDS WITHOUT BEING ADVISED BY AN EXPERIENCED MAST CELL PROVIDER.
• Heparin is very heat sensitive. Plasma heparin must be kept cold. One study reported that a tourniquet on the upper arm for ten minutes before drawing the sample increased the change of detecting mast cell activation with this test.
• Chromogranin A is influenced by many other conditions and medications. It is important that those other conditions be ruled out. This may require lengthy body scans and other tests. Chromogranin A is influenced by proton pump inhibitors, meds that are commonly taken by mast cell patients. DO NOT STOP MEDS WITHOUT BEING ADVISED BY AN EXPERIENCED MAST CELL PROVIDER.

For more detailed reading, please visit these posts:

The Provider Primer Series: Mediator testing

Patient questions: Everything you wanted to know about tryptase

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 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 difference between CD117+ and CKIT+

Hey, everyone –

I received a request to clarify the difference between being CD117+ and CKIT+.

CD117 is a receptor on the outside of mast cells. It is normal and all mast cells are CD117+. This is how we identify them as mast cells. If you have a bone marrow biopsy done and it says no CD117 is found, this is not because there are no mast cells there. It is because the test for CD117 isn’t sensitive enough to find those few mast cells. This is called the limit of detection (LoD).

When there is more of something present, it is easier to find it. Say I am in a field and there are five tennis balls scattered. If I walk around for a long time, maybe I will find three tennis balls. But if there is only one tennis ball to be found, I may not find it. I have less of a chance of finding it because there aren’t as many so it’s harder.

Being CD117+ is NORMAL for mast cells. It just means that it’s a mast cell. But mast cells that are constantly activated have more CD117+ on their outside membranes. Think of it like the tennis balls – if there are five CD117 receptors on a mast cell, it’s easier for the test to find one. If there is only one, the test might miss it.

CD117 is also called the CKIT receptor. It is a receptor that gives mast cells the signal to stay alive and encourage more mast cells to mature. If you get a biopsy report back and it is CD117+, then it will say CD117. The reason the report doesn’t call it positive for CKIT is historical and has to do with the fact that it was identified first as CD117 and later called CKIT because of similarities with other proteins of similar names.

When mast cell patients say CKIT+, it is a misnomer. It means that they are positive for the D816V mutation in CKIT, which is a marker for systemic mastocytosis. So being CD117+ and CKIT+ are not the same. CD117+ just means mast cell. CKIT+ (D816V) means neoplastic mast cell.

The D816V mutation changes the shape of the CD117 (CKIT) receptor and tells the mast cell to stay alive and encourage other mast cells to mature even when it shouldn’t.

Being CD117+ does not affect medication profile for mast cell disease at all. It just means it’s a mast cell. Some drugs are approved only for CKIT- patients (negative for D816V).

CD117/CKIT is a tyrosine kinase, which is a kind of protein. There are hundreds of known tyrosine kinases, CD117/CKIT is just one. Tyrosine kinase inhibitors can affect cells by blocking the signal to stay alive. Tyrosine kinases do not take up tyrosine from the environment, it has literally nothing to do with tyrosine metabolism at all.

If there any questions, ask in the comments.

MCAS: Blood, bone marrow and clotting

One of the reasons MCAS is so difficult to diagnose is because it often has no effect on routine blood work.  Mast cells leave the bone marrow early in their lives, circulate in the blood stream very briefly, and then live in peripheral tissues for life spans of several months to about three years.  The reason many MCAS patients have no obvious hematologic abnormalities is that mediator release in these peripheral tissues usually doesn’t affect generation of blood cells or the blood cells already circulating. 
Hematologic issues are more commonly found in proliferative disease, like SM.  Still, one study found that in SM patients, random bone marrow biopsies missed the diagnosis 1/6 of the time.  For patients in whom SM is suspected, a second BMB can be helpful and bilateral biopsies are being ordered more frequently. 
MCAS patients very rarely have increased numbers of mast cells, spindled cells, CD2/25 receptor expression or the CKIT D816V mutation.  On examination of marrow, when irregularities are found, they are off a mild “myeloproliferative/myelodysplastic” nature, which sometimes leads to a diagnosis of MDS.  These patients do not respond to MDS treatments.
When serum tryptase is less than twice the upper limit of normal, BMB is not recommended due to how infrequently abnormalities are found.  Even during reactions, MCAS patients usually have normal tryptase values.  In recent years, a tryptase of 20% + 2 ng/ml above baseline has become regarded as evidence of activation, but this is not universally accepted.
MCAS patients often have normal blood counts, white blood cell differentials and bone marrow findings.  But there is now a growing population of MCAS patients with evident abnormalities.  Elevation of monocytes is the most common irregularity, followed by elevation of eosinophils, and then elevation of basophils.  High reactive lymphocytes are often identified in these patients on manual differential.  White blood counts can be high or low, often for no clear reason, and usually mild, but sometimes severe.  Likewise, platelets can be high or low, which sometimes garners patients a diagnosis of essential thrombocytosis or immune thrombocytopenia. 
Overproduction of red blood cells can occur to excessive release by mast cells or other cells of mediators stimulating production.  Sometimes patients are originally diagnosed with and treated for polycythemia vera, but do not improve. 
Poor clotting and easy bruising is found in a lot of MCAS patients due to activation that releases heparin.  By itself, it does not typically require treatment.  The bleeding is often localized, such as excessive bleeding from a surgical site but clotting correctly elsewhere.  Antihistamines typically help, with protamine being reserved for severe cases and transexamic acid and aminocaproic acid being reserved for the most severe.
Thromboembolism, formation of a clot in one vessel that breaks away and impedes blood flow in another vessel, is not rare in MCAS patients, even those with normal coagulation labs.  Some patients have low or high PT or PTT values.  Antiphospholipid syndrome should be excluded. 
Heparin released by mast cells activates anti-thrombin III and factor XII, which activate the rest of the intrinsic clotting cascade.  Heparin also stimulates the formation of bradykinin, which in turn causes vascular dilation and loss of fluid volume from the vessels into the tissues.  This is notable as a non-histamine route that can cause angioedema, low blood pressure and fainting in MCAS patients.

References:
Afrin, Lawrence B. Presentation, diagnosis and management of mast cell activation syndrome.  2013.  Mast cells.
Sur R. Cavender D. Malaviya R. Different approaches to study mast cell functions. Int. Immunopharmacol. 2007 May; 7(5):555-567.
Butterfield JH, Li C-Y. Bone marrow biopsies for the diagnosis of systemic mastocytosis: is one biopsy sufficient? Am. J. Clin. Pathol. 2004; 121:264-267.