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What is Mast Cell Activation Syndrome (MCAS)?


"It's hard to imagine a disease more complex than mast cell activation disease..." - Dr. Afrin

Mast cells, a type of blood cell, plays a critical role in the body’s immune system. Mast cells reside in all body tissues and form part of the body’s defense system by being responsible for immediate allergic reactions. Mast cells create and store mediators and releases them when a foreign substance is present inside of the body, an allergen, or when there is an injury. For a healthy person, these chemical mediators act beneficially to heal and protect the body. However, for a person who has MCAS, these chemicals are inappropriately triggered and released, resulting in a negative effect on the body. When someone has MCAS, their body interprets different triggers (foods, exercise, chemicals, fragrances, stress, etc.) as a foreign substance/allergen and then the body releases mediators to initiate an allergic reaction. This essentially means that people with MCAS have sensitive mast cells and can have an allergic reaction to any and many things. MCAS causes a wide range of unpleasant, sometimes debilitating, symptoms that often affect several different systems of the body at the same time. It is important for patients to identify and avoid their triggers, but this is can be extremely difficult and often times the process of discovering new triggers never really ends.

Quick facts

Prevalence: Rare disorder, but the specific number is unknown. MCAS affects both children and adults.


Often Associated With:

  • Ehlers-Danlos Syndrome

  • Postural Orthostatic Tachycardia Syndrome (POTS)

  • Autism

  • Chronic Fatigue Syndrome

  • Lupus

  • Fibromyalgia

  • Lyme Disease

  • Multiple Sclerosis

Symptoms: (wide ranging and depends on the individual)

  • Itching, rashes, hives, skin turning red, swelling

  • Inflammation

  • Digestive discomfort, abdominal pain, nausea, vomiting, diarrhea

  • Chronic pain

  • Tachycardia (rapid pulse)

  • Hypotension (low blood pressure)

  • Dizziness/fainting

  • Wheezing, shortness of breath, cough, chest pain

  • Anxiety

  • Difficulty concentrating

  • Headaches

  • Brain fog

  • Fatigue

  • Insomnia

  • Itching, tightness/closure, and hoarseness of the throat

Triggers: (depends on the individual and can change over time)

  • Chemicals

  • Food/drinks

  • Heat/cold

  • Exercise

  • Medications

  • Stress (emotional and physical)

  • Fatigue

  • Infections

  • Venoms

  • Sun

  • Fragrances

Areas Affected: Affects all systems, organs, and tissue of the body! Specifically affecting…

  • Skin

  • Liver

  • Spleen

  • Lymph nodes

  • Bones/bone marrow

  • Gastrointestinal system

  • Lungs

  • Eyes

  • Blood

  • Heart

Severity: Unpleasant, to completely debilitating, to anaphylaxis (life-threatening)


Diagnosis: It is often difficult for patients to receive a diagnosis and to find a doctor who has the time and experience with MCAS. The diagnosis criteria relies on symptoms, evidence of mediator release and response to medication, as well as ruling out any other potential diseases. There is no definitive test for MCAS, but blood work (looking at tryptase, histamine, and prostaglandin) can support a diagnosis.


Treatment: There is no cure for MCAS, but avoiding triggers can help improve quality of life. There are also medications that can help limit aspects of reactions from occurring.

  • Epinephrine (EpiPen): In the case of anaphylaxis, should be used in addition to seeking medical attention

  • Antihistamines: Can be effective for itching, abdominal pain, and flushing (second generation antihistamines are preferable due to fewer side effects)

  • Histamine type 2 receptor blockers: Can be helpful for abdominal pain and nausea

  • Aspirin: Can reduce flushing

  • Montelukast and Zafirlukast: Can help reduce wheezing and abdominal cramping

  • Corticosteroids: Helpful for edema, hives, and wheezing (but should only be used as a last resort)

  • Omalizumab: Helps reduce mast cell reactivity and sensitivity to activation, which can reduce anaphylactic episodes

Timeline: The onset of MCAS is often sudden and patients commonly notice a dramatic change in symptoms after years of mild symptoms. Symptoms are often episodic and vary in intensity. For some patients, symptoms worsen over time.

 

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