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Writer's pictureDr. Thalia

How MMP-9 is helpful in the diagnosis and treatment of Mast Cell Activation Syndrome?



The diagnosis of Mast Cell Activation Syndrome (MCAS) can be a challenging one as many of the tests available are markers for chemicals that are in the body for only a short-period of time. If you don’t catch it at the most opportune moment, it may go missed completely.


The traditional testing for the MCAS spectrum includes:

  • In blood,

    • Plasma Histamine

    • Tryptase

    • Chromagranin A


  • Via 24-hour urine collection,

    • Methyl-histamine

    • Prostaglandin D2


The blood testing of histamine and tryptase in particular are the most tricky as they do not remain in blood very long after exposure to something that causes histamine elevation. If these two show up, you have to pay attention as it really doesn’t come around often.


In addition to elevations in the above tests, symptom resolution and/or improvement with antihistamines also supports a diagnosis of MCAS.


What is MMP-9 (Matrix Metaloproteinase-9)?


MMP-9 is an enzyme that can be easily tested through a blood test that is involved in inflammation, tissue repair and considered a key effector in allergic reactions.


When in balance, this enzyme helps with tissue repair, wound healing, building blood vessels to tissues, bone remodeling, memory and learning and more.


When out of balance, this enzyme sets up a cascade of inflammatory chemicals. Inflammation can be all good for a short period of time, but when inflammation becomes long-term, uncomfortable symptoms follow.


What we know from research, is that the more MMP-9 released from mast cells the more active the mast cells become.


Okay, so… What’s the big deal about MMP-9?


Within our in-office study, we have found some interesting trends to help us better understand our Mast Cell Activation Syndrome patients.


Here is the summary of our findings:

  • Clinically, we found that patients with an MMP-9 of 450 or greater had a higher likelihood of Mast Cell Activation Syndrome symptoms


  • When those patients implemented a low histamine diet, we found that their MMP-9 went down by 38% and they observed symptoms improvement in digestion, allergies, skin, mood, memory, energy, blood sugar balance and blood pressure stability with standing up


  • When patients did antihistamines along with the low histamine diet, their MMP-9’s only went down 11% and had less profound symptom improvement


  • If someone with a high baseline MMP-9 ate a high histamine meal immediately prior (within 10-15 minutes) to their blood draw, their MMP-9 went up 57%


How does this information help the big picture?


It gives us a way of monitoring progress where other markers may or may not be available. The fact is that a low histamine diet is challenging and it is so nice to have numbers to show where you are. At the end of the day, trends are our friends.


As a doctor, this also shows me at what stage adding in anti-histamines (herbal and/or pharmaceutical) will actually be helpful and effective.


If this is a piece of your overall picture, you definitely want to know about it as bringing down this inflammation can make an enormous shift in the right direction.


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Hi Dr Thalia,


Do I understand right that the antihistamines + low histamine diet group actually had more MMP 9 than the group who were just on the low histamine diet?


Asking because I'm currently doing both antihistamines & low histamine diet.


Thanks in advance

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