Dr. Reena Mehta

Uptown Allergy and Asthma

What are Mast Cells?

Mast cells are allergy cells responsible for allergic reactions. They cause allergic symptoms by releasing products called “histamine mediators” stored inside them. Mast cells can be activated by foods, medications, infections, insects, and many other potential allergic triggers.

Sometimes mast cells become defective and release mediators because of abnormal internal signals. Certain mutations in mast cells can produce an increased amount of mast cells that overproduce and spontaneously release histamine. These abnormal mast cells can grow uncontrollably and cause a variety of mast cell disorders, such as mastocytosis or mast cell activation syndrome.

What is Mast cell Activation Syndrome (MCAS)? Mast Cell Activation Syndrome is a condition in which a patient experiences repeated episodes of allergic symptoms, such as hives, swelling, low blood pressure, difficulty breathing and severe diarrhea. High levels of mast cell mediators are released during those episodes. The episodes respond to treatment with antihistamines or blockers of mast cell mediators.

What is the link between Ehlers Danlos Syndrome (EDS) & MCAS? Researchers believe that there is a link between MCAS and EDS. Mast cells adhere to proteins called fibronectin and vitronectin in the extracellular matrix, and this interaction can release various inflammatory molecules. Since EDS is caused by defects in collagen, these mutations can lead to changes in mast cell behavior, leading to MCAS. A proportion of people with hypermobile EDS (hEDS) can also have MCAS. In one study (Afrin et al. Am J Med Genet Part C Semin Med Genet 175C:226–236), 66% of patients with both a high heart rate when standing (Postural Tachycardia Syndrome or POTS) and EDS also had symptoms consistent with MCAS.

What can you expect at your first visit with the Allergist? On your first visit, the physician will review your history, focusing your main concerns. This is followed by a physical exam and diagnostic testing. The first visit typically lasts about 1 hour where the physician will try to determine if you have MCAS. We will perform allergy testing to understand your allergic triggers and the physician will also obtain orders for bloodwork for a formal MCAS evaluation.

Please discontinue antihistamines for 5 days prior to your visit to perform accurate allergy testing. Decongestants without antihistamines may be taken. If you have any questions about antihistamines in your medication regimen, please contact your allergist for guidance.