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Patient questions: Everything you wanted to know about tryptase

I get a lot of questions about tryptase.

Tryptase is one of the most well characterized mast cell mediators and the first to be unique to mast cells. Serum tryptase is the most well known test for systemic mastocytosis and anaphylaxis. But mast cell patients sometimes test negative, complicating their lives and care.

There are a lot of reasons why mast cell patients test negative for tryptase. One reason is that a lot of the understanding of anaphylaxis hinged upon the ability of mediators to get quickly to the bloodstream to quickly spread to various organ systems. While this does happen, not all mediators move at the same speed. Tryptase is released from granules as large complexes with other mediators, like heparin. It takes time for it to dissociate enough to be active.

Tryptase also does a lot of things and breaks down lots of things. If there are things for it to break down in the immediate environment, it will still break them down whether or not you are having anaphylaxis. Eventually, the tryptase that wasn’t used up breaking things down gets to the bloodstream. This is why the ideal time to test for tryptase in blood is about 90-120 minutes after an allergic event/severe reaction/anaphylaxis. Following severe reaction/anaphylaxis, it can take about two weeks for tryptase to return to baseline.

The reason that most patients with systemic mastocytosis have high tryptase levels is because they have more mast cells and many mast cells secrete tryptase at rest. This means that even if they aren’t activated, they will still release tryptase regularly. The reason why baseline tryptase level is such an important marker for SM is because it distinguishes mastocytosis from anaphylaxis.

However, we have learned a lot about tryptase in the last several years, and it doesn’t seem like all mast cells secrete tryptase all the time. Mast cells are heavily influenced by their environment and the cells around them. Some mast cells make more tryptase than others and some release tryptase regularly and some don’t.

About 80-90% of SM patients have a baseline tryptase over 20 ng/ml. This means they tested over 20 ng/ml on two separate occasions when they had not recently had a severe event. But not all SM patients have elevated tryptase, but that doesn’t mean they don’t have more mast cells than usual. It is possible that their mast cells are concentrated in places in the body where tryptase will be used up before it gets to the bloodstream or that it will take too long to get there for the test to catch it. There is some evidence that tryptase testing is less reliable in overweight and obese women, and I’m sure that’s true. Some mast cells live in adipose tissue and that tissue is harder for large molecules to move through, like tryptase.

Our understanding of MCAS is that there is aberrant mast cell behavior without an abnormal number of mast cells. These patients generally have repeat negative biopsies and so the assumption is that they definitely don’t have SM. But tryptase is a crummy test and I think as a community we can’t really know if they have too many mast cells until we have more robust tests. I’m not saying MCAS patients have too many mast cells, but I’m saying I don’t really trust tryptase for detection of reaction/anaphylaxis in MCAS patients or, to be frank, in anyone.

So why do we still use tryptase if it’s a crummy test? It’s not a crummy test for everything. In particular, it is a very good indicator of disease progression (ISM to SSM to ASM) in patients who have a lot of mast cells. A steadily increasing tryptase level means that there is increased proliferation and can indicate moving to a state where organ damage is more likely. So it is helpful for those people. It’s not helpful for everyone else.

Tryptase testing is not affected in a meaningful way by any medications that I can think of. Mast cell stabilizers can decrease degranulation, but tryptase can also be released in other ways, and there has not been any demonstration that mast cell stabilizers are effective enough to affect this test. Antihistamines/other meds/steroids don’t affect tryptase level.

There was a consensus paper that came out several years ago in which it was posited that an increase in tryptase level of 2 ng/ml + 2% from baseline was indicative of mast cell activation and could be used in the diagnosis of MCAS. This is not widely agreed to in the US and the data supporting this has never been published so I personally understand the reluctance of providers to acknowledge this as a marker of mast cell activation.

The other big reason why mast cell patients may test normal for tryptase is that their reactions/anaphylaxis are not mediated by a pathway that triggers tryptase release like IgE does.  IgG activation and other pathways do not always demonstrate tryptase release.

I think I got everything. If you have more questions about tryptase, let me know.

Kounis Syndrome: Diagnosis (Part 2 of 4)

Separating the symptoms of the coronary syndrome from those caused by the coincident allergic reaction is difficult.  Acute chest pain is the hallmark symptom of Kounis Syndrome. While other symptoms may be present, such as nausea, fainting, and shortness of breath, they can also be attributed to the allergic reaction.  Likewise, many of the clinical markers for KS may also appear during anaphylaxis, including cold extremities, very fast or very low heart rate, low blood pressure, palpitations, and sweating. Given the significant overlap in presentation with allergic symptoms, KS is not often diagnosed, though it likely affects a larger population than represented in literature.

Troponins and cardiac enzymes like creatinine kinase are important markers for coronary syndrome, but they are not always elevated in KS. Measurement of mast cell mediators like histamine or tryptase is not always accurate due to the short lifetime of these molecules in the body.  Released histamine is only present in blood for about eight minutes, while tryptase has a half-life of about ninety minutes.

An electrocardiogram (EKG) should be performed as part of the diagnostic process.  A number of signs have been seen in KS patients, including atrial or ventricular fibrillation, bigeminal rhythm, heart block, nodal rhythm, sinus bradycardia or tachycardia, ST segment depression or elevation, T-wave flattening or inversion, QRS or QT prolongation, and ventricular ectopics.  Beyond EKG, there are additional markers that may be present with Kounis Syndrome.  A chest x-ray may show an enlarged heart.  Echocardiogram may show dilated cardiac chambers. Angiography of the coronary artery can reveal spasm or thrombosis. In coronary biopsies, infiltration by mast cells and eosinophils may be found.  Elevation of eosinophils in the blood may also be present.

Having no history of coronary artery disease can make diagnosis more complicated for KS Type I patients, who also may have normal troponins and EKG. Dynamic cardiac MRI with gadolinium can show a subendocardial lesion in patients with KS Type I. Newer imaging techniques such as SPECT have been able to identify myocardial ischemia in KS Type I where coronary angiography had showed no irregularities.

References:

Kounis NG, et al. Kounis Syndrome (allergic angina and allergic myocardial infarction). In: Angina Pectoris: Etiology, Pathogenesis and Treatment 2008.

Lippi G, et al. Cardiac troponin I is increased in patients admitted to the emergency department with severe allergic reactions. A case-control study. International Journal of Cardiology 2015, 194: 68-69.

Kounis NG, et al. The heart and coronary arteries as primary target in severe allergic reactions: Cardiac troponins and the Kounis hypersensitivity-associated acute coronary syndrome. International Journal of Cardiology 2015, 198: 83-84.

Fassio F, et al. Kounis syndrome: a concise review with focus on management. European Journal of Internal Medicine 2016; 30:7-10.

Kounis Syndrome: Aspects on pathophysiology and management. European Journal of Internal Medicine 2016.

Kounis NG. Kounis syndrome: an update on epidemiology, pathogenesis, diagnosis and therapeutic management. Clin Chem Lab Med 2016

Kounis NG. Coronary hypersensitivity disorder: the Kounis Syndrome. Clinical Therapeutics 2013, 35 (5): 563-571.

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.

Cardiovascular manifestations of mast cell disease (Part 1 of 5)

Mast cells are present in the cardiovascular system under normal conditions both in the heart and near vasculature, often in spaces close to nerve endings.  They perform a variety of necessary functions including participating in the pathway to generate the hormone angiotensin II, which encourages an increase in blood pressure.  Mast cells in the heart and vasculature are usually positive for both chymase and tryptase in granules. Mast cells in the cardiovascular system have also been tied to a number of conditions, including atherosclerosis, arrhythmias and aneurysm.

Mast cell patients may experience a number of cardiovascular symptoms or events. 29% of SM patients and at least 20% of MCAS patients report palpitations and supraventricular tachycardia.  31% of patients with mast cell activation disease (MCAS, MMAS, SM) experience episodic or chronic elevation in arterial blood pressure due to mast cell activation. Ventricular fibrillation, cardiac arrest and Kounis Syndrome can occur in mast cell patients due to mast cell activation.  Few cases of heart failure in SM patients have been reported.

Kounis Syndrome is an acute coronary syndrome provoked by mast cell mediator release. In one series, ten mast cell patients (5 MCAS, 3 MMAS, 2 ISM) suffered acute coronary syndromes.  These patients reported “oppressive” chest pain of the type commonly seen in ischemic cardiac events.  The triggers for these events were diverse: venom immunotherapy, mepivacaine, exercise, penicillin, general anesthesia, wasp sting, metamizole and moxifloxacin.  In seven patients, the echocardiogram was normal.  In the remaining, left ventricular hypertrophy, anteroseptal hypokinesia, medioapical hypokinesia, inferoseptal akinesis, lateral apical akinesia and left ventricular ejection fraction of 40% were found on echo. Only six patients had elevation of troponin, a test commonly used to diagnose heart attack and acute coronary syndromes.

Mast cell mediators exhibit a wide range of effects on the cardiovascular and nervous systems. Mast cell mediators can affect release of norepinephrine by sympathetic nervous system, contributing to arrhythmias.  In some instances, release of norepinephrine has been linked to sudden cardiac death, although not linked specifically to mast cell patients. Histamine actually decreases norepinephrine release by binding to H3 receptors on nerve endings.

As mentioned above, mast cells participate in modulating the level of angiotensin II. Mast cells release renin, which leads to the formation of angiotensin II. Angiotensin II then binds to AT1 receptors on sympathetic nerve endings, raising blood pressure. Angiotensin II can also cause arrhythmias without involving the nervous system.

References:

Kolck UW, et al. Cardiovascular symptoms in patients with systemic mast cell activation disease. Translation Research 2016; x:1-10.

Gonzalez-de-Olano D, et al. Mast cell-related disorders presenting with Kounis Syndrome. International Journal of Cardiology 2012: 161(1): 56-58.

Kennedy S, et al. Mast cells and vascular diseases. Pharmacology & Therapeurics 2013; 138: 53-65.

Explain the tests: Complete blood cell count (CBC) – White blood cell count (Part five)

White blood cells, also called leukocytes, are key functionaries of the immune system.  There are several types of white blood cells and each is specialized for certain types of immune response.

White blood cell levels are useful for pointing to many conditions.  They can be high or low for many reasons.  They are commonly used to determine whether or not a patient has an infection.  A “left shift” in the white count indicates presence of high numbers of immature white cells, often called bands.  A left shift can occur for a number of reasons.  It is a natural response to infection as the body tries to make enough white cells to fight the infection.  A “right shift” refers to the absence or low level of bands, new white cells.  This indicates suppression of bone marrow.

Normal range for white blood cell count:

  • 0-11.0 x 109 cells/L

Types of white blood cells can be quantified as either a percentage of total white cells or as an absolute count.  Normal white cell count varies with age, especially neutrophils, lymphocytes and monocytes.

Normal range for neutrophil count:

  • 8-7.7 x 109 cells/L
  • 35-80% of total white cells

Normal range for eosinophil count:

  • 0-0.8 x 109 cells/L
  • 0-4% of total white cells

Normal range for lymphocyte count:

  • 8-4.8 x 109 cells/L
  • 18-44% of total white cells

Normal range for monocyte count:

  • 2-0.9 x 109 cells/L
  • 7-12.5% of total white cells

Normal range for basophil count:

  • 0-0.1 x 109 cells/L
  • 0-1.2% of total white cells

Explain the tests: Complete blood cell count (CBC) – High white blood cell count (Part seven)

High white blood cell count is called leukocytosis. High white blood cell count is often due to a healthy process, such as immune defense or inflammatory response after an injury.

Reasons for leukocytosis:

  • Infection response, especially bacterial infection
  • Inflammation
  • Physical stress and tissue death
  • Allergic disease
  • Proliferative diseases of white blood cells, such as leukemias

Conditions that cause tissue death and elevate white blood cells:

  • Physical trauma
  • Surgery
  • Ischemia
  • Heart attack
  • Burns

Allergic conditions that elevate white blood cells:

  • Allergic reaction, acute or chronic
  • Anaphylaxis
  • Asthma
  • Atopic disease

Inflammatory conditions that cause elevation of white blood cells:

  • Autoimmune diseases such as rheumatoid arthritis
  • Inflammatory bowel diseases

Medications that trigger excessive production of white blood cells:

  • Corticosteroids
  • Beta agonists

 

Explain the tests: Complete blood cell count (CBC) – Low white blood cell count (Part six)

Low white blood cell count is called leukopenia. Due to mast cell involvement in many bodily processes, leukopenia can occur for many reasons.

Reasons for leukopenia:

  • Bone marrow suppression
  • Disorder of white cell production or white cell precursors
  • Proliferative disease of other cell types in the bone marrow
  • Mechanical destruction of white blood cells, as in splenomegaly (swollen spleen)

Some conditions that interfere with making enough white blood cells:

  • Certain infections, such as tuberculosis, malaria, dengue fever, Lyme disease and viral infections
  • Sepsis
  • Nutritional deficiency, such as low copper or zinc
  • Nutritional toxicity of certain minerals, such as arsenic

Some proliferative diseases that interfere with making white blood cells:

  • Hodgkin’s lymphoma
  • Myelofibrosis

Conditions that affect white cell precursors:

  • Aplastic anemia
  • Myelodysplastic syndrome
  • Damage to precursors by radiation exposure or chemotherapy

Conditions that cause damage to white cells:

  • Splenomegaly, swollen spleen
  • Lupus

 

Medications that interfere with making enough white blood cells:

  • Immunosuppressants, like mycophenolate, cyclosporine and TNF blockers
  • Interferon preparations, like Betaseron
  • Other medications like clozapine, bupropion, minocycline, lamotrigine and valproic acid
  • Chemotherapy
  • Radiation

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

One study assessed whether mast cell count would be influenced depending on which part of the organ biopsies were taken from. While the difference in count was not large, it is worth considering that these counts all straddle the cut off of 20 mast cells/hpf.  This means that patients with the same GI symptoms could have biopsies with over or under 20/hpf depending on the site of the biopsy.  See Table 24 for details.

Table 24: Effect of sampling site on mast cell count/hpf in colon of chronic diarrhea patients
Zare-Mirzaie A, et al. Analysis of colonic mucosa mast cell count in patients with chronic diarrhea. Saudi J Gastroenterol 2012; 18 (5): 322-326.
Microscopy method: 400x magnification, mast cells counted in 5 hpf and averaged
Visualization: Tryptase (IHC), toluidine blue
Rectum Sigmoid Descending colon Transverse colon Ascending colon Cecum
20.5±5 18.3±3.5 22.6±3.9 20.7±4.9 25.5±6.7 22.1±4.9

 

The same paper also looked at effect of season on mast cell count.  There was no significant difference, but again, the range of biopsies in each season straddles the 20/hpf line. See Table 25 for details.

Table 25: Effect of season on mast cell count in colon of diarrhea patients
Zare-Mirzaie A, et al. Analysis of colonic mucosa mast cell count in patients with chronic diarrhea. Saudi J Gastroenterol 2012; 18 (5): 322-326.
Microscopy method: 400x magnification, mast cells counted in 5 hpf and averaged
Visualization: Tryptase (IHC), toluidine blue
Spring Summer Fall Winter
20.6±4.7 24.2±4.9 19.5±3.9 20.3±4.9

 

The most telling portion of this study compared mast cell counts when using a simple stain (toluidine blue) and when using IHC (antibody for tryptase) to find mast cells in biopsies.  Mast cells are not easy to see on biopsy.  They require special stains, and even then, they are hard to see.  Immunohistochemistry (IHC) uses antibodies to identify markers on cells that are easier to see with a microscope.  It is not uncommon for unfamiliar doctors to refuse the use of IHC testing (which usually includes CD117, CD25, CD2 or tryptase) in lieu of commonly available stains in the lab.  However, even stains that visualize mast cells are inferior to IHC methods.  In biopsies taken from all parts of the colon, toluidine blue staining showed less than half of the mast cells visualized using IHC for tryptase.  This means that when IHC testing isn’t ordered, counts reported by simple staining are much lower than the true count. See Table 26 for details.

Table 26: Comparison of mast cell count in biopsies stained with toluidine blue and with tryptase antibody (IHC)
Zare-Mirzaie A, et al. Analysis of colonic mucosa mast cell count in patients with chronic diarrhea. Saudi J Gastroenterol 2012; 18 (5): 322-326.
Microscopy method: 400x magnification, mast cells counted in 5 hpf and averaged
Visualization: Tryptase (IHC) and toluidine blue
Staining method Rectum Sigmoid Descending colon Transverse colon Ascending colon Cecum
IHC 20.5±5 18.3±3.5 22.6±3.9 20.7±4.9 25.5±6.7 22.1±4.9
Toluidine blue 8.5±0.7 6.8±1.2 10.3±4.2 10.3±3.5 12.5±5 8.1±2.9
% of cells identified by IHC seen by toluidine blue staining 41% 37% 46% 50% 49% 37%

 

There are other factors that contribute to lack of consensus in mast cell counts in GI tissue. One of the biggest causes is that not all labs use standard size high powered fields.  HPF is usually 0.25mm2, but it is not uniform throughout the research world.  Many papers don’t even provide the size of their high powered fields.  More than that, many papers report mast counts per mm2 without providing conversion factors so it’s not always possible to compare results from one paper to another.  There were some papers I wanted to use for this series that I couldn’t because I couldn’t be sure that I could convert their mast cells/mm2 confidently to mast cells/hpf.

Together with the fact that number of hpf counted, methods of biopsy slide preparation, stains and IHC antibodies are variable, it is hard to get a real understanding of whether the cut off of 20 mast cells/hpf is meaningful.  It is my finding that there are a number of conditions that cause mast cells/hpf to be higher than controls in an experiment.  It is also my finding that in some experiments, control subjects have baseline mast cell counts over 20 mast cells/hpf. It is reasonable to assume that inflammatory GI conditions can cause mast cell hyperplasia.  But the fact that chronic urticaria patients often have mast cell counts higher than control subjects is also telling.  It speaks to the fact that an allergic process can elevate mast cell counts in a space where there is no appreciable symptomology. If patients have reactions to “pseudoallergens” as described in that paper, then it is possible that these reactions could drive the increase in mast cell count in the GI tract.  If this is true, then the many mast cell patients who have “pseudoallergen” responses could see an increase in GI mast cell burden as a result of their mast cell disease.

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.

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

The 2014 Doyle paper provides mast cell counts in colon biopsies for healthy controls, MCAS, and IBS. Mast cells were identified using antibodies for tryptase, CD117, CD25 and CD30 (IHC). Mast cells were counted in both one HPF in the densest portion of the slide and in five HPF and averaged.  In the densest portion of the slide, mast cell counts were higher in 1 HPF than in the average of 5 HPF.  Differences in methodology such as this can contribute to lack of consensus on what constitutes too many mast cells. See Table 21 for details.

Table 21: Comparison of mast cell count in 1 HPF and in the average of 5 HPF
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.
Microscopy method: 400x magnification, mast cells counted in 1 hpf
Visualization: IHC for tryptase, CD117, CD25 and CD30
HPF Control group A:

Healthy controls

 Control group B:

MCAS

 Control group C:

IBS
Average Range Average Range Average Range
Average of 5 hpf 19 mast cells/hpf 7-39 mast cells/hpf 20 mast cells/hpf 12-31 mast cells/hpf 23 mast cells/hpf 9-45 mast cells/hpf
1 hpf 26 mast cells/hpf 11-55 mast cells/hpf 28 mast cells/hpf 14-48 mast cells/hpf 30 mast cells/hpf 13-59 mast cells/hpf

 

Other papers also investigated factors that could contribute to differences in mast cell counts. The 2015 Sethi paper evaluated differences in GI mast cell counts between men and women.  Women had  marginally higher counts in both IBS and control groups. See Table 22 for details.

Table 22: Difference in mast cell count between men and women with chronic diarrhea and asymptomatic controls
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.
Microscopy method: 400x magnification, mast cells counted in 5 hpf and averaged
Visualization: CD117 (IHC)
Sample type Study group: Women Study group: Men Control group: Women Control group: Men
Colon Average Range Average Range Average Range Average Range
30 mast cells/hpf 27-34 mast cells/hpf 27 mast cells/hpf 24-31 mast cells/hpf 24 mast cells/hpf 22-37 mast cells/hpf 21 mast cells/hpf 19-24 mast cells/hpf
Diffuse scattered cells, no clusters. Diffuse scattered cells, no clusters. Diffuse scattered cells, no clusters. Diffuse scattered cells, no clusters.

 

One paper looked at the difference in mast cell count in the rectum of healthy patients over the age of 55 and under.  Please note that these counts were made using a much lower magnification than other papers in this series, so mast cell counts are not directly comparable. Mast cells were identified using antibodies to tryptase (IHC). See Table 23 for details.

Table 23: Differences in GI mast cell count in healthy patients over and under 55 years of age.
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.
SPECIAL NOTE: THESE COUNTS WERE MADE AT HALF THE MAGNIFICATION OF OTHER PAPERS IN THIS SERIES.  THESE MAST CELL COUNTS ARE NOT DIRECTLY COMPARABLE TO OTHER STUDIES.
200x magnification, number of hpf not explicitly stated, assumed mast cells counted in 1 hpf
Visualization: Tryptase (IHC)
Sample type Study group: Healthy, over 55 years old Study group: Healthy, under 55 years old Control group B:

No control group
Rectum Average Range Average Range Average Range
40.5 ± 2.4 mast cells/hpf 51.7 ± 4.1 mast cells/hpf N/A N/A

 

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.

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

A 2007 paper assessed the reliability of CD25 on GI mast cells as a marker of systemic mastocytosis. This study determined mast cell burden in stomach, small intestine and colon of patients with SM and compared it to patients with urticaria pigmentosa, various inflammatory GI conditions and healthy controls. Mast cells were detected using antibodies for tryptase and CD25 (IHC) and counted in 10 hpf and averaged.

In the stomach, SM patients averaged 57 mast cells/hpf, compared to 14/hpf for urticaria pigmentosa patients; 23.7/hpf for other inflammatory GI conditions; and 12/hpf for healthy controls.  Conditions other than SM that caused over 20 mast cells/hpf in the stomach were H. pylori positive gastritis and bile reflux esophagus.  Some healthy controls also had a count of 20/hpf or higher. See Table 17 for details.

In the small intestine, SM patients averaged 175 mast cells/hpf; urticaria pigmentosa, 22 mast cells/hpf; other inflammatory GI conditions, 20.3 mast cells/hpf; and healthy controls, 27 mast cells/hpf in the duodenum and 32 mast cells/hpf in the terminal ileum. Conditions other than SM that caused over 20 mast cells/hpf in the small intestine were peptic duodenitis, celiac disease, irritable bowel syndrome and eosinophilic enteritis.  See Table 18 for details.

In the colon, SM patients averaged 209 mast cells/hpf; urticaria pigmentosa, 13/hpf; other inflammatory GI conditions, 20.4/hpf; and healthy controls, 21/hpf. Conditions other than SM that caused over 20 mast cells/hpf in the colon were ulcerative colitis, Crohn’s colitis, lymphocytic colitis, irritable bowel syndrome and parasitic infection.  See Table 19 for details.

Table 17: Mast cell count in stomach of patients with systemic mastocytosis
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.
Microscopy method: 400x magnification, mast cells counted in 10 hpf and averaged
Visualization: Tryptase and CD25 (IHC)
Sample type Study group: Systemic mastocytosis Study group: Urticaria pigmentosa Study group: Inflammatory GI conditions Control group A:Healthy control
Stomach Average Range Average Range Average Range Average Range
57 mast cells/hpf 24-90 mast cells/hpf 14 mast cells/hpf 10-17 mast cells/hpf 23.7 mast cells/hpf 6-23.3 mast cells/hpf 12 mast cells/hpf 5-21 mast cells/hpf
Clusters/dense infiltrates or confluent sheets. Diffuse scattered cells, no clusters. Diffuse scattered cells, no clusters. Diffuse scattered cells, no clusters.

 

Table 18: Mast cell count in small intestine of patients with systemic mastocytosis
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.
Microscopy method: 400x magnification, mast cells counted in 10 hpf and averaged
Visualization: Tryptase and CD25 (IHC)
Sample type Study group: Systemic mastocytosis Study group: Urticaria pigmentosa Study group: Inflammatory GI conditions Control group A:Healthy control
Small intestine Average Range Average Range Average Range Average Range
175 mast cells/hpf 74-339 mast cells/hpf 22 mast cells/hpf 12-32 mast cells/hpf 20.3 mast cells/hpf 17.5-33 mast cells/hpf 27 mast cells/hpf(duodenum)32 mast cells/hpf (terminal ileum) 4-51 mast cells/hpf (duodenum)21-40 mast cells/hpf (terminal ileum) 

 
Clusters/dense infiltrates or confluent sheets. Diffuse scattered cells, no clusters. Diffuse scattered cells, no clusters. Diffuse scattered cells, no clusters.

 

Table 19: Mast cell count in colon of patients with systemic mastocytosis
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.
Microscopy method: 400x magnification, mast cells counted in 10 hpf and averaged
Visualization: Tryptase and CD25 (IHC)
Sample type Study group: Systemic mastocytosis Study group: Urticaria pigmentosa Study group: Inflammatory GI conditions Control group A:Healthy control
Colon Average Range Average Range Average Range Average Range
209 mast cells/hpf 110-301 mast cells/hpf 13 mast cells/hpf 8-19 mast cells/hpf 20.4 mast cells/hpf 12.1-33.4 mast cells/hpf 21 mast cells/hpf 10-31 mast cells/hpf
Clusters/dense infiltrates or confluent sheets. Diffuse scattered cells, no clusters. Diffuse scattered cells, no clusters. Diffuse scattered cells, no clusters.

 

Table 20: Inflammatory GI conditions associated with mast cell over 20/hpf in at least one biopsy
Stomach Small intestine Colon
Gastritis from H. pylori infection Peptic duodenitis Ulcerative colitis
Bile reflux gastropathy Celiac disease Crohn’s disease colitis
Healthy stomach tissue Irritable bowel syndrome Collagenous colitis
Eosinophilic enteritis Lymphocytic colitis
Healthy duodenum and ileum Irritable bowel syndrome
Parasitic worm infection
Eosinophilic colitis
Healthy colon tissue

 

A 2014 paper (Doyle 2014) summarized results of GI biopsies from various locations for patients with systemic mastocytosis.  Mast cell count in SM patients ranged from 20-278/hpf, with an average of 116/hpf. Most biopsies in SM patients contained clusters of mast cells or confluent sheets. 25% of positive biopsies had only one cluster of mast cells. 21% showed multiple clusters within a biopsy while other biopsies from the same region showed no mast cells.  Three biopsies from SM patients showed dispersed cells that were CD25+.

In actual practice, many doctors do not take a variety of biopsies, especially if there is no gross abnormality visualized during scoping.  This highlights the need to test for CD25. It also provides evidence that while clustering is a defining characteristic of SM, in some tissue spaces, clustering may be absent despite being present elsewhere in the same organ.

Positivity for some markers associated with systemic mastocytosis, but not enough to receive a diagnosis of SM per WHO criteria, yields a diagnosis of monoclonal mast cell activation syndrome (MMAS).  Patients with MMAS display clonality of mast cells despite not meeting criteria for SM.  In research circles, MMAS is sometimes referred to as preclinical SM.  It is possible that MMAS represents a very early stage of SM.  MMAS is managed the same way as SM and markers of clonality (25% or more mast cells in a hpf spindle shaped, positivity for CD25 and/or CD2 receptor(s), clustering of mast cells in groups of 15 or more, positivity for CKIT D816V mutation, serum tryptase baseline of 20 ng/ml or higher) should be taken seriously as an indication of proliferative mast cell disease.

 

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.