Learn More About MCAS

MCAS — Mast Cell Activation Syndrome

  • Mast Cell Activation Syndrome (MCAS) is a rare disorder that effects the immune system, but more specifically, mast cells. Mast cells are responsible for allergic reactions by producing histamine. MCAS occurs when the body mast cells constantly release histamine into the body’s blood stream causing allergic reaction systems frequently.

    MCAS symptoms may be present at birth or may develop later in childhood or adulthood. MCAS often present alongside other conditions such as Ehlers Danlos Syndrome (EDS), Marfans Syndrome, and Dysautonomia. However the connection between these conditions is not yet fully understood.

    A similar condition to MCAS is known as Mastocytosis. The different between the two conditions is that MCAS occurs when the mast cells in the body release too much histamine where Mastocytosis occurs when the body produces too many mast cells.

    There are currently 3 identified types of MCAS:

    • Primary MCAS — MCAS with a known mutation in the body’s mast cells

    • Secondary MCAS — MCAS resulting as a comorbidity of another condition

    • Idiopathic MCAS — MCAS without a known or identifiable cause

    MCAS is a rare disease that affects roughly 0.01% of the population. MCAS mainly affects women, but it can also affect men.

    Each person with MCAS experiences symptoms differently, however, some possible triggers include:

    • Allergic-type triggers

      • Insect bites, high histamine foods

    • Drug induced triggers

      • Antibiotic, Ibuprofen, Opiates

    • Stress related triggers

      • Anxiety, pain, rapid temperature changes, exercise, overly tired, infections

    • Smells

      • Perfume, smoke

  • Symptoms can vary between cases of MCAS and everyone has different MCAS triggers.

    Some possible symptoms include:

    • Skin symptoms: itching, flushing, hives, sweating, swelling, rash

    • Eye symptoms: irritation, itching, watering

    • Nose symptoms: itching, running

    • Mouth and throat symptoms: itching, swelling in your tongue or lips, swelling in your throat

    • Lung symptoms: trouble breathing, wheezing

    • Heart and blood vessel symptoms: low blood pressure, rapid heart rate

    • Stomach and intestine symptoms: cramping, nausea, diarrhea, abdominal pain

    • Nervous system symptoms: headache, confusion, fatigue

    • In severe episodes: rapid drop in blood pressure, weak pulse, anaphylaxis

      • Anaphylaxis: When your airway swells and shuts (in response to an allergen) — this requires emergency treatment (911) and a shot of epinephrine (EpiPen)

  • When MCAS is suspected, a patients full history and symptoms are compared to the MCAS diagnostic criteria.

    MCAS is a hard condition to test for as testing is often done during a MCAS flare/reaction which can be hard to time.

    Some tests that might be ordered to diagnose MCAS include:

    • IgE blood test

    • 24 hour N-methylhistamine urine test

    • serum tryptase

    Another important piece needed to diagnose MCAS is a positive reaction to medications used to treat MCAS.

  • A key component of treating MCAS consists of experimenting with certain drugs and identifying your MCAS triggers to find the right balance, as everyone experiences MCAS symptoms and triggers differently.

    Some lifestyle changes can include:

    • low histamine diet — limiting food high in histamine

    • low FODMAP diet — limiting foods high in certain sugars

    Some drug treatments can include:

    • H1 or H2 Antihistamines → they block the effects of histamines (what mast cells release to cause allergic reactions)

      • H1 → Histamine type 1 receptor blockers (diphenhydramine and loratadine) can help with MCAS symptoms like itching and stomach pain

      • H2 → Histamine type 2 receptor blockers (ranitidine and famotidine) can treat MCAS symptoms like stomach pain and nausea

    • Aspirin → Can decrease flushing

    • Mast cell stabilizers → Mast cell stabilizers such as Omalizumab can help prevent the release of mediators from mast cells resulting in fewer episodes of anaphylaxis

    • Antileukotrienes → Antileukotrienes, such as zafirlukast and montelukast, block the effects of leukotrienes which are responsible for wheezing and stomach cramp symptoms

    • Corticosteroids → last resort for treatment of edema, wheezing, or hives

  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3753019/#:~:text=The%20diagnosis%20requires%20that%20a,in%20patients%20whose%20serum%20tryptase

    https://www.mastcellaction.org/about-mcas#:~:text=Triggers%20can%20include%20fragrances%2C%20exercise,time%20within%20the%20same%20person.

    https://www.aaaai.org/conditions-treatments/related-conditions/mcas