Systemic mastocytosis (SM) constitutes a rare hematologic condition characterized by the abnormal buildup of mast cells, resulting in unpredictable GI manifestations. In as many as 85% of SM patients, these reactions impact the gastrointestinal tract, establishing the gut as a frequently involved site.
A meal that sits well one day might bring on cramping or diarrhea the next, and these symptoms are real. SM is characterized by the release of histamine and other chemicals that trigger inflammation and allergy-like reactions.
SM and the Gut
Kara Wada, MD, FAAAAI, DiplABLM, a quadruple-board-certified physician specializing in allergy, immunology, and lifestyle medicine, explained that the gut has more mast cells than almost anywhere else in the body. These mast cells sit exactly where the nerves, blood vessels, and immune system meet, making people with SM susceptible to GI symptoms when mast cells become overactive.
The chemical histamine, for example, increases stomach acid and speeds up motility, or how quickly food moves through the gut. Because the nerves and mast cells in the gut communicate with each other, stress may worsen GI symptoms, Dr. Wada added.
GI Symptoms of SM
Chancellor Donald, MD, an oncologist-hematologist, explained that in advanced SM, GI symptoms may also develop when abnormal mast cells accumulate in the lining of the digestive tract, interfering with organ function. Common GI symptoms of SM may include abdominal pain, diarrhea, bloating, constipation, acid reflux, and feeling full quickly.
These symptoms are often caused by mast cell mediators and may respond to medications that block those chemicals. Dr. Wada said mast cells may be the cause when GI symptoms follow triggers such as heat, alcohol, exercise, or stress and are accompanied by flushing, itching, or lightheadedness.
In the middle of understanding and managing SM, it is essential to recognize that the condition’s impact on the gut is not just a matter of individual symptoms, but also a complex interplay between the immune system, nerves, and mast cells. This complexity highlights the need for an approach to diagnosis and treatment that considers the unique characteristics of each patient’s condition.
Diagnosis Challenges
Dr. Wada emphasized that a thorough evaluation to identify or rule out other possible causes of symptoms may be more helpful than focusing on whether they fit one specific diagnosis. Symptoms alone are not enough to confirm a diagnosis, and doctors may order tests such as blood tests, genetic testing, or biopsies to determine the underlying cause of GI symptoms.
SM symptoms can also mimic another mast cell disorder, mast cell activation syndrome (MCAS), especially because specialists may use different diagnostic criteria. Dr. Wada recommended that patients consider seeing an SM specialist if their current care team has limited experience diagnosing and treating mast cell disorders.
Dr. Wada recommends taking H1 and H2 antihistamines on a regular schedule rather than only when symptoms appear. Other treatments include leukotriene blockers, proton-pump inhibitors (PPIs), and targeted therapies.
Lifestyle changes can also help manage symptoms, including following an eating plan that reduces inflammation, eating fiber-rich foods, and identifying triggers by removing and slowly reintroducing foods with guidance from a care team or a dietitian. Getting enough sleep and staying physically active are also important, as sleep loss can lower reaction thresholds measurably, Dr. Wada said.
Managing SM Complications
Dr. Donald explained that SM-related GI symptoms can interfere with daily life, but on their own, they don’t usually mean the condition is worsening. However, certain symptoms may signal complications or disease progression, such as poor nutrient absorption, unexplained weight loss, low levels of albumin, an enlarged liver or spleen, or GI bleeding.
Advanced SM may require KIT-targeted treatment rather than antihistamines alone. If a doctor recommends an endoscopy, patients should ask whether their tissue samples will be tested for mast cells, as standard laboratory processing can miss mast cells in tissue samples.
Patients should inform their care team if they experience any of these problems, so they can determine whether more testing is needed.
Importance of Specialized Care
She explained that a thorough evaluation can help identify or rule out other possible causes of symptoms, and that a treatment plan can make a significant difference in managing GI symptoms.
