What is the treatment for Mast Cell Activation Syndrome (MCAS)?

Treatment of Mast Cell Activation Syndrome (MCAS)

The most effective treatment for Mast Cell Activation Syndrome (MCAS) is a combination of trigger avoidance, H1 and H2 antihistamines, mast cell stabilizers like oral cromolyn sodium, and emergency medications for acute reactions. 1

First-Line Treatment Approach

• Identify and avoid known triggers of mast cell activation, including temperature extremes, mechanical irritation, alcohol, and certain medications (aspirin, radiocontrast agents, specific anesthetics) 1, 2
• Use nonsedating H1 antihistamines as first-line therapy, which can be increased to 2-4 times standard dose if needed 1
• Add H2 antihistamines to help attenuate cardiovascular symptoms and as first-line treatment for gastrointestinal symptoms 1
• Incorporate oral cromolyn sodium, particularly effective for gastrointestinal symptoms (bloating, diarrhea, abdominal cramps) and neuropsychiatric manifestations 1, 3

Acute Management of Mast Cell Activation Episodes

• All patients with a history of systemic anaphylaxis should carry two epinephrine autoinjectors and use them for severe reactions, especially hypotension or laryngeal angioedema 1, 2
• Administer albuterol via nebulizer or metered-dose inhaler for bronchospasm symptoms 1
• Measure serum tryptase within 30-120 minutes of symptom onset during acute reactions for diagnostic confirmation 1, 2

Additional Targeted Therapies

• Consider leukotriene receptor antagonists (e.g., montelukast) for gastrointestinal symptoms, especially with elevated urinary LTE4 levels 2
• Cyproheptadine (H1 antihistamine with antiserotonergic properties) may help alleviate gastrointestinal symptoms 2
• For skin symptoms, use moisturizers, water-soluble sodium cromolyn cream, and topical corticosteroids 1, 2

Special Considerations

Perioperative Management

• Implement a multidisciplinary approach with surgical, anesthesia, and perioperative medical teams 2
• Provide pre-anesthetic treatment including anxiolytics, H1 and H2 antihistamines, and possibly corticosteroids 2
• Use safer anesthetic agents such as propofol, sevoflurane, isoflurane, fentanyl, and remifentanil 1, 2
• Avoid muscle relaxants atracurium and mivacurium 2

Pregnancy Management

• Employ a multidisciplinary team including high-risk obstetrics, anesthesia, and allergy specialists 1, 2
• Focus on trigger avoidance, prophylactic antihistamines, and as-needed corticosteroids 2

Refractory MCAS Treatment Options

• For patients who don't respond to standard antimediator therapy, omalizumab may be considered 4
• Omalizumab doses typically range from 150 mg every 4 weeks to 300 mg every 3 weeks, with higher doses (≥300 mg/month) potentially offering better response 4
• The majority of patients with refractory MCAS show at least partial response to omalizumab, with some achieving complete response 4

Common Pitfalls and Caveats

• Sedating H1 antihistamines should be used with caution, particularly in elderly patients, as they may cause drowsiness, impair driving ability, and lead to cognitive decline 1
• Pain should not be left untreated, as it can trigger mast cell activation 1
• Aspirin may reduce flushing and hypotension in some patients but is contraindicated in those with allergic reactions to NSAIDs 1
• Doxepin (potent H1 & H2 antihistamine with tricyclic antidepressant activity) may reduce CNS manifestations but can cause drowsiness, cognitive decline, and increase suicidal tendencies in children and young adults with depression 1
• MCAS is often misdiagnosed as functional gastrointestinal disorders, leading to significant delays in diagnosis and appropriate treatment 5, 6