What is the treatment for mast cell activation syndrome?

Treatment of Mast Cell Activation Syndrome (MCAS)

The treatment of mast cell activation syndrome requires a stepwise approach focused on trigger avoidance, antihistamines, mast cell stabilizers, and targeted symptom management to reduce morbidity and improve quality of life.

First-Line Management Strategies

Trigger Avoidance

• Identify and avoid known triggers of mast cell activation 1
• Common triggers include:
  • Temperature extremes (hot or cold)
  • Mechanical irritation
  • Alcohol
  • Certain medications (aspirin, radiocontrast agents, specific anesthetic agents)

Pharmacologic Treatment

H1-Antihistamines

• Nonsedating H1 antihistamines are preferred first-line therapy 1
• Can be increased to 2-4 times the standard dose if needed
• Target symptoms: pruritus, flushing, urticaria, dermatographism, tachycardia
• Sedating H1 antihistamines (like diphenhydramine) may be useful but can cause drowsiness and cognitive impairment, especially in elderly patients 1

H2-Antihistamines

• First-line therapy for gastrointestinal symptoms 1
• Help H1 antihistamines attenuate cardiovascular symptoms
• Examples: ranitidine, famotidine

Mast Cell Stabilizers

• Oral cromolyn sodium is FDA-approved for mastocytosis 2
• Particularly effective for gastrointestinal symptoms (abdominal bloating, diarrhea, cramps)
• May also improve neuropsychiatric manifestations
• Dosing recommendation: Start with divided doses and gradually increase to target dose to improve tolerance 1

Acute Management of Mast Cell Activation Episodes

Emergency Treatment

• Epinephrine autoinjector for patients with history of anaphylaxis or airway angioedema 1
• Patients should be trained to:
  • Use epinephrine promptly when needed
  • Assume supine position for hypotensive episodes
  • Use inhaled bronchodilators (albuterol) for bronchospasm 1

Post-Episode Management

• Serum tryptase level should be checked within 30-120 minutes of symptom onset 1
• Compare to baseline tryptase level after recovery
• Consider allergic workup including specific IgE testing and skin testing 1

Additional Targeted Therapies

For Gastrointestinal Symptoms

• Cromolyn sodium is particularly effective 2, 3
• Leukotriene receptor antagonists (e.g., montelukast) may help, especially with elevated urinary LTE4 levels 1
• Cyproheptadine (an H1 antihistamine with antiserotonergic properties) may help with GI symptoms 1

For Skin Symptoms

• Topical treatments:
  • Skin moisturizers to prevent dryness
  • Water-soluble sodium cromolyn cream for urticaria and pruritus (2-4 times daily)
  • Topical corticosteroids for inflammation 1

For Refractory Symptoms

• Aspirin may reduce flushing and hypotension in some patients, particularly those with increased urinary 11b-PGF2a levels
  • Use with caution as it's contraindicated in those with allergic reactions to NSAIDs 1
• Short-term corticosteroids for severe flares (initial oral dosage of 0.5 mg/kg/day with slow taper over 1-3 months) 1
• Omalizumab has shown benefit in preventing anaphylactic episodes in some patients 1

Special Considerations

Perioperative Management

• Multidisciplinary approach involving surgical, anesthesia, and perioperative medical teams 1
• Pre-anesthetic treatment with:
  • Anxiolytics (benzodiazepines)
  • H1 and H2 antihistamines
  • Possibly corticosteroids 1
• Safer anesthetic agents include:
  • Propofol (induction)
  • Sevoflurane or isoflurane (inhalational)
  • Fentanyl or remifentanil (analgesics)
  • Lidocaine, bupivacaine (local anesthetics) 1
• Avoid muscle relaxants atracurium and mivacurium; rocuronium and vecuronium may be safer 1

Pregnancy Management

• Multidisciplinary team including high-risk obstetrics, anesthesia, and allergy specialists 1
• Focus on trigger avoidance, prophylactic antihistamines, as-needed corticosteroids
• Ensure epinephrine availability for anaphylaxis 1

Common Pitfalls to Avoid

1. Delayed diagnosis: MCAS is often mistaken for functional gastrointestinal disorders, leading to significant delays in proper treatment 3

2. Inadequate antihistamine dosing: Standard doses may be insufficient; higher doses (2-4× standard) may be needed 1

3. Withholding pain management: While caution is needed with opiates, pain itself can trigger mast cell activation and should be properly managed 1

4. Overlooking trigger identification: Detailed history to identify specific triggers is essential for management 1

5. Failure to prepare for procedures: Surgical and invasive procedures require specific preparation to prevent mast cell activation 1