Mast cell activation syndrome (MCAS) is one type of mast cell activation disorder (MCAD), and is an immunological condition in which mast cells inappropriately and excessively release chemical mediators, resulting in a range of chronic symptoms such as as hives, swelling, low blood pressure, difficulty breathing, congestion and severe diarrhea. Mediators released include leukotrienes, histamines, prostaglandin, and tryptase.
Unlike mastocytosis, another type of MCAD, where patients have an abnormally increased number of mast cells, patients with MCAS have a normal number of mast cells that do not function properly and are defined as “hyper-responsive”.
There are no known causes. The condition may be mild until exacerbated by stressful life events, or symptoms may develop and slowly trend worse with time.
The symptoms most consistent with anaphylaxis are:
• Heart related symptoms: rapid pulse (tachycardia), low blood pressure (hypotension) and passing out (syncope).
• Skin related symptoms: itching (pruritus), hives (urticaria), swelling (angioedema) and skin turning red (flushing).
• Lung related symptoms: wheezing, shortness of breath and harsh noise when breathing (stridor) that occurs with throat swelling.
• Gastrointestinal tract symptoms: diarrhea, nausea with vomiting and crampy abdominal pain.
This condition can be difficult to diagnose, especially since many of the numerous symptoms are non-specific in nature. Although different diagnostic criteria are published, a commonly used strategy to diagnose patients is to use all three of the following:
- Symptoms consistent with chronic/recurrent mast cell release:
Recurrent abdominal pain, diarrhea, flushing, itching, nasal congestion, coughing, chest tightness, wheezing, lightheadedness (usually a combination of some of these symptoms is present)
- Laboratory evidence of mast cell mediator (elevated serum tryptase, N-methyl histamine, prostaglandin D2 or 11-beta- prostaglandin F2 alpha, leukotriene E4 and others)
- Improvement in symptoms with the use of medications that block or treat elevations in these mediators”.
We recommend a Low Histamine Diet in conjunction with Mast Cell stabilisers (ketotifen, Quercetin), Antihistamines and/or anti-inflammatory drugs.