Mast Cell Activation Syndrome

"Mast Cell Activation Syndrome (MCAS) is a chameleon and difficult to identify for many reasons. It presents with different symptoms-which are often inflammatory or allergic in nature-to different degrees in different places in the body", according to Lawrence B Afrin, M.D., Hematology/Oncology, Medical University of South Carolina To make matters worse, many healthcare practitioners are not yet familiar with the condition and there is relatively little information about the syndrome in the medical literature.

Mast cells are immune cells produced in the bone marrow. They are involved with allergic reactions, anaphylaxis and have a protective role defending us against pathogens. Mast cells are present in most tissues characteristically surrounding blood vessels and nerves. They are especially prominent on the surfaces of the body including the skin, digestive tract, nose and lungs and are also found in a connective tissue, joints and the brain.

The typical presentation of MCAS is extremely diverse due to the widespread distribution of mast cells throughout the body. Mast cells contain over 60 different types of inflammatory mediators, which upon release, can adversely affect virtually any tissue or organ resulting in a diverse set of symptoms. The condition usually starts in childhood or adolescence and continues with variable and seemingly unrelated symptoms over a lifetime.

When mast cells degranulate and release mediators the symptoms may include flushing, itching, rapid heart rate, abdominal cramps, lightheadedness, headaches, shortness of breath, swollen lymph nodes, joint and muscle pain, fatigue, cognitive impairment, urinary symptoms, fluctuating blood pressure, weakness, dizziness, anaphylaxis, sinusitis, anxiety, chemical sensitivities, fibromyalgia and many more.

The symptoms can be chronic, persistent or recurrent. They often wax and wane and tend to be inflammatory or allergic in nature. Patients may have relatively symptom-free periods alternating with times of feeling miserable. The symptom-free periods shorten and eventually become chronic and fluctuate with an overall downhill trend.

MCAS is likely a very prevalent condition often at the root of many chronic symptoms leading to decades of misdiagnosis and mismanagement. The condition is mainly diagnosed based on history, symptoms, and physical examination rather than laboratory testing. Laboratory testing may or may not help confirm the diagnosis. The usual tests include serum tryptase, plasma heparin and histamine and urinary N-methylhistidine (a metabolite of histamine). These tests are best collected when the patient is having a flare of symptoms. The test results are often normal despite symptoms strongly correlated with a diagnosis of MCAS.

At this time MCAS is not curable, but can usually be controlled. The cornerstone of therapy is avoidance of identifiable causes of mast cell release. A multitude of nonspecific environmental factors can trigger mast cell release including allergies, alcohol, medications, foods, mold, chemicals, pollens, stress, infection and temperature changes. Treatments are highly individualized depending on specific symptoms and complications. Medications may include antihistamines, mast cell membrane stabilizers, anti-inflammatories and desensitization. Patients with MCAS usually have a normal lifespan, but quality of life may range from episodic mild discomfort to severe impairment sufficient to cause disability and inability to work.

MCAS is not the same as systemic mastocytosis because the mast cells are not necessarily being over produced or accumulating. In either case, the mast cells are inappropriately activated causing abnormal release of inflammatory cell mediators, which can potentially affect every organ system.