What is Mast Cell Activation Syndrome (MCAS) and its Relationship to IBS?

I recently wrote a post about suffering from a rare connective tissue disorder known as Ehlers Danlos Syndrome (usually known as EDS) and its intersection with IBS. But another medical condition that is usually co-morbid with EDS, is MCAS--which is the acronym for Mast Cell Activation Syndrome. MCAS also has a strong correlation to IBS.

What is MCAS?

A mast cell is a kind of blood cell in the body that reacts to and attempts to manage foreign bodies and injury by releasing chemical mediators, such as histamine. However, in a person with MCAS, this process is either overactive--with the body releasing too many mast cells at even slight disruption, and/or the person develops a sensitivity to the release of mast cells.¹ It can be very difficult to correctly diagnose MCAS as levels of different markers can fluctuate. Sometimes it can be determined by a blood test, though more often, the better method is to try a 24-hour urine test (the person must abstain from taking any NSAIDs or anti-histamine medications for several days before the test). Even then though, the results are not always conclusive. More recently, some experts on MCAS think that an endoscopy with a biopsy of cells in the stomach may be a superior way to determine if someone has MCAS.² MCAS also has been found to share a gene mutation with EDS, so if someone has EDS, it is likely they may possibly have MCAS as well (those with this gene mutation also suffered from IBS is higher percentages).³

The connection between MCAS and IBS

Several prevalent symptoms of MCAS are related to digestion and include abdominal pain, bloating, heartburn/reflux disease, diarrhea and vomiting. Even for those who do not have formal diagnoses of MCAS, mast cells can contribute to IBS symptoms. One peer review study found noted that "low grade inflammatory infiltration, often rich in mast cells, in both the small and large bowel, has been observed in some patients with IBS" and that "therapies targeting mast cells...have been tried in IBS patients, and have partially exhibited considerable efficacy" in relieving symptoms.⁴ Basically, MCAS can cause allergic-type reactions related to digestion even if you do not have any technical food allergies (by releasing mast cells and histamine). As such, adopting a low-histamine diet or taking antihistamines or other medications that regulate mast cells could have benefits for IBS patients.

If you suspect you have MCAS, you may want to inquire about it to your doctor and see if you can get tested.

Do you have MCAS or suspect you have it and how has it impacted your IBS? Did you find treating your MCAS helped your IBS too? Please weigh in below!