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

Management Approach for Mast Cell Activation Syndrome (MCAS)

The primary treatment for MCAS involves a stepwise approach focused on trigger avoidance, antihistamines, mast cell stabilizers, and management of acute episodes with epinephrine when necessary. 1

Diagnosis Confirmation

Before initiating treatment, ensure proper diagnosis using these criteria:

• Recurrent symptoms consistent with mast cell mediator release affecting ≥2 organ systems
• Documented increase in mast cell mediators (e.g., serum tryptase) during symptomatic periods
• Response to medications that target mast cell mediators
• Exclusion of other conditions

Treatment Algorithm

First-Line Interventions

1. Trigger Identification and Avoidance

   • Common triggers include:
     • Temperature extremes
     • Mechanical irritation
     • Alcohol
     • Certain medications (aspirin, radiocontrast agents, specific anesthetics)
     • Insect venoms
     • Physical/emotional stress

2. Pharmacologic Management

   • H1 Antihistamines:

     • Nonsedating options (cetirizine, fexofenadine) preferred
     • Can be increased to 2-4 times standard dosing
     • Target symptoms: flushing, pruritus, urticaria, tachycardia 1

   • H2 Antihistamines:

     • First-line for gastrointestinal symptoms
     • Help attenuate cardiovascular symptoms when combined with H1 blockers 1

   • Mast Cell Stabilizers:

     • Oral cromolyn sodium (200mg QID)
     • Particularly effective for gastrointestinal symptoms (diarrhea, abdominal pain)
     • Also helps with urticaria, pruritus, flushing, and cognitive function
     • Clinical improvement typically occurs within 2-6 weeks 2

Second-Line Interventions

• Leukotriene Modifiers:

  • Montelukast or zileuton for bronchospasm or persistent GI symptoms
  • Most effective when urinary LTE4 levels are elevated 1

• Aspirin:

  • May reduce flushing and hypotension in selected patients
  • Contraindicated in those with NSAID reactions
  • May require dosing up to 650mg twice daily 1

• Corticosteroids:

  • For refractory symptoms: Initial dose 0.5 mg/kg/day with slow taper over 1-3 months
  • For procedure preparation: 50mg prednisone at 13 hours, 7 hours, and 1 hour before procedures 1

• Omalizumab:

  • Consider for prevention of recurrent anaphylactic episodes
  • Particularly useful for those requiring insect venom immunotherapy 1

Specialized Medications

• Doxepin: Potent H1/H2 antihistamine with antidepressant properties; useful for neuropsychiatric manifestations 1

• Cyproheptadine: Sedating H1 antihistamine with antiserotonergic properties; helpful for gastrointestinal symptoms 1

• Ketotifen: Sedating H1 antihistamine; available as compounded tablets in the US 1

Acute Management of Mast Cell Activation Episodes

1. Epinephrine Autoinjector:

   • All patients with history of systemic anaphylaxis or airway angioedema should carry and be trained to use 1
   • If used, patient should be transported to emergency department while remaining supine

2. Positioning:

   • Supine positioning for hypotensive episodes
   • Use bedpan for diarrhea and emesis basin after rolling to side 1

3. Bronchodilators:

   • Albuterol via nebulizer or metered-dose inhaler for bronchospasm 1

Special Considerations

Surgical Procedures

• Preoperative Planning:

  • Multidisciplinary approach involving surgical, anesthesia, and perioperative medical teams
  • Review prior anesthetic records and identify/avoid known triggers
  • Avoid temperature extremes and unnecessary trauma 1

• Pre-anesthetic Treatment:

  • Benzodiazepines for anxiety
  • H1 and H2 antihistamines
  • Consider corticosteroids 1

• Safer Anesthetic Agents (though evidence is anecdotal):

  • Induction: propofol
  • Inhalational: sevoflurane or isoflurane
  • Analgesics: fentanyl or remifentanil
  • Local anesthetics: lidocaine, bupivacaine 1

• Agents to Avoid:

  • Muscle relaxants: atracurium and mivacurium
  • Succinylcholine
  • Use caution with opiates (codeine, morphine) 1

Pregnancy Management

• Multidisciplinary approach with high-risk obstetrics, anesthesia, and allergy specialists
• Continue antihistamines and mast cell stabilizers as needed
• For severe refractory cases, interferon-alfa may be considered
• Avoid cladribine, imatinib, and midostaurin during pregnancy 1

Monitoring and Follow-up

• Regular assessment of symptom control
• Periodic measurement of serum tryptase levels
• Evaluation for disease progression or development of comorbidities
• Adjustment of medications based on response and side effects

By following this comprehensive management approach, patients with MCAS can experience significant improvement in symptoms and quality of life.