Mast cells are immune cells that contribute to the pathology of inflammation, allergies, and autoimmune-based disorders. They are found throughout the body and mast cell mediators contribute to the symptoms of allergy and anaphylaxis. Mediators include cytokines, prostaglandins, leukotrienes, histamine, serotonin, tryptase, and chymase.
Clinical presentation may include urticaria, chronic fatigue, fibromyalgia, IBS, interstitial cystitis, endometriosis, angioedema, and/or multiple food, drug, chemical, and environmental sensitivities.
Genetic mutations and external triggers can contribute to excess or inappropriate activation of mast cells, systemic mastocytosis (rare), and mast cell activation syndrome (MCAS) which is more common.
Testing:
Preferred: increase in serum total tryptase (more specific to MCAD)
Other acceptable measures: serum histamine/urinary metabolites, serum PGD2/urinary metabolites
Blood testing for the c-KIT D816V mutation, commonly present in mastocytosis
Initial laboratory workup with CBC, CMP, TSH, thyroid antibodies, and lipid panel can be within normal limits.
24-hour urine testing collected during a flare revealed elevated urinary metabolites of Prostaglandin F2 and Prostaglandin D2.
For a more in-depth review we recommended reading
Naturopathic Doctor News & Review - "Mast Cell Activation Syndrome"
For a comprehensive overview of MCAS assessment and diagnosis, we recommend Afrin et al’s “A concise, practical guide to diagnostic assessment for mast cell activation disease”.
Afrin, Lawrence B., and Gerhard J. Molderings. "A concise, practical guide to diagnostic assessment for mast cell activation disease." World Journal of Hematology 3.1 (2014): 1-17.