A mild MCAS reaction (while on medication)

Photo is of a mild MCAS reaction while on an anti-mediator regimen. It shows flushing/rash on the face and chest 

If you know me personally, you probably know that I have a lot of “allergies” and sensitivities to foods, medications, and environmental agents (grass, pollen, detergents etc…). My reactions range from increased severity of migraine, to GI distress, to hives/anaphylaxis. What you likely don’t know is that don’t have any IgE-mediated (traditional) allergies at all, and my reactions to each of things I avoid is unpredictable each time I encounter them. This stumped allergists until recently, when I was diagnosed with Mast Cell Activation Syndrome (MCAS), also sometimes called Mast Cell Activation Disorder (MCAD), and a member of the broader family of Mast Cell Disorders.


What are Mast Cell Disorders? 

Mast Cell Disorders are a group of conditions caused by overproduction or dysfunction of the mast cells. Mast cells are produced in the bone marrow and reside in connective tissues throughout the body (skin, lining of the digestive tract and airway, etc…). In healthy bodies, these cells play a part in immune defense and wound healing. They are also the cells that respond by releasing “mediators” such as tryptase and histamine during an allergic reaction that then cause inflammation in conditions such as allergic asthma, allergic rhinitis, and allergic anaphylaxis. In mastocytosis, the body overproduces mast cells and they accumulate in one or more organ system. In MCAS, there are a normal number of mast cells that overreact to triggers in the environment and release mediators that cause inflammation. The reactions can range from unpleasant to life threatening in severity. MCAS is more common than mastocytosis, but also a much newer diagnosis.


What are the symptoms of Mast Cell Disorders? 

Mast cell disorders usually present with some but not necessarily all of the following symptoms: flushing, dermatographia (lightly scratching the skin allows you to “write” on it because it turns red), itching, skin rashes, hives, fatigue, headache, difficulty concentrating, nausea, acid reflux, abdominal pain, vomiting, constipation/diarrhea, musculo-skeletal pain, difficulty breathing, difficulty swallowing, coughing and chest tightness.

Some diagnoses that may be signs of mast cell activation include: idiopathic urticaria (hives), idiopathic anaphylaxis, non-allergic rhinitis, non-allergic asthma, Irritable Bowel Syndrome (IBS), acid reflux (GERD), eczema, multiple chemical sensitivity, histamine intolerance, autonomic dysfunction, psoriasis, Chronic Fatigue Syndrome/ME and Fibromyalgia.


How do they relate to EDS &  Dysautonomia?

MCAS (and less frequently mastocytosis) are commonly seen alongside hereditary hypermobile connective tissue disorders (such as EDS), as well as in patients who have POTS (Post Orthostatic Tachycardia Syndrome) or other forms autonomic dysfunction. The presence of all three disorders in one person (such as myself) is frequent enough that this tricky trifecta of conditions is being studied by multiple researchers – some of whom believe that EDS causes POTS/Dysautonomia and MCAS, others believe that the autonomic dysfunction is the root problem, and still others believe that the mast cells themselves are the link between the three conditions. Dr. Milner, a researcher at NIH has found one gene that links all three conditions in some patients – he calls this condition Familial Tryptasemia.  While doctors work to determine the causality of the relationship between these illnesses (which will hopefully lead  to improved treatment options) it is safe to assume that if you have one or two of these conditions and have symptoms of another, they should be evaluated by physician who is familiar with the illness in question.


How are Mast Cell Disorders Diagnosed?

Mast Cell disorders are difficult to diagnose, because the labs and biopsies that are required are finicky. They must be taken during a flare, and they must be handled properly. Mastocytosis is usually diagnosed via bone marrow biopsy, although skin and GI biopsies may also be useful. Tests used to diagnose MCAS include:

  • Serum Tryptase within a 2 hr window after reaction (blood test)
  • 24 HR urine test to look for histamine and prostaglandin levels (This test frequently results in a false negative because either the patient or the lab did not refrigerate the sample properly – it must be kept cold at all times)
  • Response to an anti-mediator regimen

Because these tests are so finicky, a clinical diagnosis of Mast Cell Activation Syndrome may be made in the absence of positive tests, if there has been an effort to rule out other possible causes, there is a history of mast cell activation symptoms, and significant improvement is made on an anti-mediator treatment regimen, and the patient is continually evaluated/followed by an allergist or mast cell specialist. This is how I was diagnosed.


How are Mast Cell Disorders Treated? 

Treatment is dependent on specific symptoms, and their severity but usually includes an anti-mediator regimen to stabilize mast cells. These usually include various antihistamines (H1 and H2 blockers). For example, my regimen includes Zyrtec, Zantac, and Singulair. Different people have success with different medications though, and the regimen should be developed and tweaked by an allergist or mast cell specialist. People with MCAS may also need to carry an EpiPen or an epinephrine auto injector. If asthma or restrictive airway is a part of the condition for a particular individual, then it should also be treated. Some people with MCAS also find relief by using a low histamine diet and/or by using an elimination diet to identify specific food triggers.



Disclaimer: I am not a doctor, or even a medical professional. I am only a patient who does her research in order to advocate for myself and others living with similar conditions. This information is not intended to serve as medical advice. Please discuss all medical concerns with your physician.