From the Guidelines
Mast cell activation syndrome (MCAS) should be treated with a combination of H1 antihistamines, H2 antihistamines, and mast cell stabilizers, as well as avoidance of personal triggers and consideration of a low-histamine diet, as recommended by the most recent guidelines 1. Mast cell activation occurs when mast cells release inflammatory mediators like histamine, prostaglandins, and leukotrienes in response to various triggers.
- Treatment typically involves:
- H1 antihistamines (such as cetirizine 10mg daily or fexofenadine 180mg daily)
- H2 antihistamines (like famotidine 20mg twice daily)
- Mast cell stabilizers (such as cromolyn sodium 200mg four times daily)
- For acute reactions, epinephrine auto-injectors should be available for severe symptoms.
- Patients should identify and avoid personal triggers, which commonly include:
- Certain foods
- Medications
- Temperature extremes
- Alcohol
- Stress
- A low-histamine diet may help reduce symptoms.
- For more severe cases, additional medications like montelukast (10mg daily) or low-dose aspirin therapy may be considered, as supported by recent guidelines 1. Mast cell activation occurs because these cells are part of the immune system and can become hypersensitive, releasing their inflammatory contents inappropriately.
- This cascade of chemical mediators causes symptoms affecting multiple body systems, including:
- Skin (flushing, hives)
- Gastrointestinal (nausea, diarrhea)
- Respiratory (wheezing)
- Cardiovascular (blood pressure changes) systems.
From the Research
Mast Cell Activation Syndrome
Mast cell activation syndrome (MCAS) is a condition characterized by the activation of mast cells, leading to the release of various mediators that can cause a range of symptoms.
- The symptoms of MCAS can affect multiple organ systems, including the skin, gastrointestinal, cardiovascular, respiratory, and neurologic systems 2.
- Patients with MCAS may experience episodic symptoms, such as urticaria, angioedema, flushing, nausea, vomiting, diarrhea, abdominal cramping, hypotensive syncope, tachycardia, wheezing, conjunctival injection, pruritus, and nasal stuffiness 2.
Diagnosis of MCAS
The diagnosis of MCAS is based on a combination of clinical symptoms and laboratory tests.
- Laboratory tests may include measurements of urinary or serum markers of MCAS, such as histamine metabolites, PGD2 or its metabolite, and 11-β-prostaglandin F2 alpha 2.
- An increase in serum tryptase levels above 15 ng/mL or an increase in tryptase levels above baseline value on one occasion may also be indicative of MCAS 2.
- A substantial transient increase in serum total tryptase or increase in other mast cell-derived mediators, such as histamine or PGD2, or urinary metabolites, may also be used to diagnose MCAS 2.
Treatment of MCAS
The treatment of MCAS typically involves the use of medications that block the effects of mast cell mediators or inhibit their release.
- H1 and H2 antihistamines, leukotriene receptor blockers, and mast cell stabilizers may be used to manage symptoms of MCAS 3, 4.
- In some cases, corticosteroids or epinephrine may be necessary to manage acute episodes of mast cell activation 3.
- Second-generation H1-antihistamines, such as rupatadine, may be effective in improving quality of life and symptom control in patients with MCAS 4.
Research Needs
Despite the growing recognition of MCAS, there are still many gaps in our understanding of the condition.
- Further research is needed to elucidate the underlying mechanisms and pathways that lead to mast cell activation in MCAS patients 5.
- Large, well-designed clinical trials are necessary to investigate the effectiveness and safety of different treatments for MCAS, including second-generation H1-antihistamines 4.
- The development of new diagnostic tests and treatments for MCAS is also an area of ongoing research 6.