How are flares in Mast Cell Activation Syndrome (MCAS) managed?

Management of Flares in Mast Cell Activation Syndrome (MCAS)

Flares in Mast Cell Activation Syndrome (MCAS) should be managed with a combination of trigger avoidance, H1 and H2 antihistamines, mast cell stabilizers like cromolyn sodium, and emergency medications including epinephrine autoinjectors for severe reactions. 1

Symptoms of MCAS Flares

MCAS flares typically affect multiple organ systems simultaneously:

• Cardiovascular: Hypotension, tachycardia, syncope
• Respiratory: Wheezing, shortness of breath
• Dermatologic: Flushing, urticaria (hives), pruritus (itching)
• Gastrointestinal: Abdominal pain, diarrhea, nausea, vomiting, bloating
• Neurological: Headaches, cognitive dysfunction
• Constitutional: Fatigue, malaise 1, 2

Trigger Identification and Avoidance

Identifying and avoiding triggers is the first-line approach for managing MCAS flares:

• Common triggers include:

  • Foods (especially high-histamine and fermented foods)
  • Temperature extremes
  • Mechanical irritation
  • Alcohol and fermented beverages
  • Certain medications
  • Ultraviolet radiation 1

• A structured elimination diet approach is recommended:

  • 4-6 week elimination phase
  • Systematic reintroduction of single foods while monitoring symptoms
  • Focus on eliminating fermented foods, high-histamine foods, histamine-releasing foods, food additives, and preservatives 1

Medication Management for Flares

First-Line Treatments:

• H1 and H2 Antihistamines:

  • Non-sedating H1 antihistamines are preferred first-line therapy
  • Target dermatologic manifestations, tachycardia, and abdominal discomfort
  • Can be combined with H2 blockers for enhanced effect 1

• Cromolyn Sodium:

  • Particularly effective for gastrointestinal symptoms (bloating, diarrhea, cramps)
  • May benefit neuropsychiatric manifestations
  • Start at lowest dose and gradually increase to 200 mg 4 times daily before meals and at bedtime
  • Clinical trials show improvement in gastrointestinal symptoms within 2-6 weeks of treatment initiation 1, 3

Second-Line Treatments:

• Leukotriene Receptor Antagonists (e.g., Montelukast):

  • Consider when urinary LTE4 levels are elevated
  • Most effective for respiratory and dermatologic symptoms
  • Work best in conjunction with antihistamines 1

• Aspirin:

  • May reduce flushing and hypotension
  • Particularly effective in patients with increased urinary prostaglandin metabolites
  • Use with caution due to risk of triggering mast cell degranulation in some patients
  • Contraindicated in those with allergic reactions to NSAIDs 1

Refractory Cases:

• Omalizumab:

  • Consider for MCAS resistant to mediator-targeted therapies
  • Reduces severity and frequency of allergic reactions
  • Can prevent spontaneous episodes of anaphylaxis 1

• Corticosteroids:

  • For severe refractory symptoms
  • Initial oral dosage of 0.5 mg/kg/day
  • Slow taper over 1-3 months
  • Not recommended for long-term use due to side effects 1

Emergency Management of Severe Flares

• Epinephrine Autoinjector:

  • Essential for patients with history of systemic anaphylaxis or airway angioedema
  • Patients should carry two autoinjectors at all times 1, 4

• Additional Emergency Measures:

  • Supine positioning for recurrent hypotensive episodes
  • Albuterol for bronchospasm symptoms
  • For prolonged severe episodes, corticosteroids may be necessary 1, 5

Special Considerations

• Premedication Protocol for Procedures/Surgery:

  • Anxiolytic agents
  • H1 and H2 blockers
  • Corticosteroids
  • Anesthesia requires special planning to avoid triggering agents 1, 4

• Photoprotection Measures (for UV-sensitive patients):

  • Avoid direct sun exposure
  • Use physical barriers (hats, sunglasses, long-sleeved clothing)
  • Apply broad-spectrum sunscreen 1

Diagnostic Confirmation During Flares

During symptomatic episodes, laboratory evidence should be collected to confirm mast cell activation:

• Serum tryptase (1-4 hours after symptom onset)
  • Must show increase of >20% + 2 ng/mL from baseline
• 24-hour urine studies showing increased:
  • N-methylhistamine
  • Prostaglandin D2 or 11β-PGF2α
  • Leukotriene E4 1, 6

Common Pitfalls in MCAS Management

• Misdiagnosing MCAS without meeting diagnostic criteria
• Failing to rule out other conditions that mimic MCAS symptoms
• Overly restrictive diets leading to nutritional deficiencies
• Delay in administering epinephrine during severe reactions
• Not addressing comorbid conditions that may exacerbate symptoms 1, 7

For optimal management, patients with suspected MCAS should be referred to specialized centers with expertise in mastocytosis/MCAS for comprehensive evaluation and personalized treatment planning 1.