Treatment for Mast Cell Activation Syndrome (MCAS)
The treatment of Mast Cell Activation Syndrome requires a comprehensive approach focused on trigger avoidance and a stepwise medication regimen targeting mast cell mediators, with H1 and H2 antihistamines forming the cornerstone of therapy. 1
First-Line Treatments
Trigger Avoidance
- Identify and avoid known triggers such as insect venoms, temperature extremes, mechanical irritation, alcohol, and certain medications (aspirin, radiocontrast agents, specific anesthetic agents) 1
Pharmacologic Management
- H1 receptor antihistamines: First-line therapy, can be increased to 2-4 times standard dose if needed; non-sedating options preferred for daily use 1
- H2 receptor antihistamines: Particularly effective for gastrointestinal symptoms and can enhance cardiovascular symptom control when combined with H1 blockers 1
- Oral cromolyn sodium: Particularly effective for gastrointestinal symptoms (bloating, diarrhea, cramps); may also help with neuropsychiatric manifestations; should be titrated gradually to 200mg four times daily before meals and at bedtime 1, 2
- Epinephrine autoinjector: Should be prescribed for patients at risk of anaphylaxis for immediate use during severe reactions 1
Second-Line Treatments
- Leukotriene receptor antagonists (montelukast, zafirlukast) or 5-lipoxygenase inhibitors (zileuton): Most effective when used in conjunction with H1 antihistamines, particularly for dermatologic symptoms 1
- Aspirin: May help with refractory flushing and hypotensive episodes by inhibiting PGD2 synthesis; should be introduced in a controlled clinical setting due to risk of triggering mast cell degranulation 1
- Doxepin: A potent H1 and H2 antihistamine with tricyclic antidepressant activity; may reduce central nervous system manifestations but can cause drowsiness and cognitive decline, particularly in elderly patients 1
Refractory Cases
- Omalizumab (anti-IgE therapy): Consider for cases resistant to mediator-targeted therapies; reduces severity and frequency of allergic reactions and can prevent spontaneous episodes of anaphylaxis 1
- Systemic corticosteroids: May help some patients but should be tapered as quickly as possible to limit adverse effects 1
Management of Acute Episodes
- For hypotensive episodes: Patient should assume supine position followed by intramuscular epinephrine administration 1
- For laryngeal angioedema: Immediate intramuscular epinephrine 1
- For bronchospasm: Intramuscular epinephrine or inhaled rapid-acting bronchodilator such as albuterol 1
- After epinephrine use, patient should consider emergency department evaluation while maintaining supine position 1
Special Considerations
Bone Health Management
- For patients with osteopenia/osteoporosis:
Perioperative Management
- Multidisciplinary approach involving surgical, anesthesia, and perioperative medical teams 1
- Pre-anesthetic treatment with anxiolytics (benzodiazepines), antihistamines (H1 and H2 blockers), and possibly corticosteroids 1
- Safer anesthetic agents include propofol, sevoflurane, isoflurane, fentanyl, remifentanil, lidocaine, and bupivacaine 1
- Avoid muscle relaxants atracurium and mivacurium; use rocuronium and vecuronium with caution 1
- Exercise caution with opiates but do not withhold needed pain control as pain can trigger mast cell activation 1
Pregnancy Considerations
- Management by multidisciplinary team including high-risk obstetrics, anesthesia, and allergy specialists 1
- Focus on symptom alleviation with medications that minimize potential harm to the fetus 1
- For severe refractory cases during pregnancy, interferon-alfa may be considered; avoid cladribine and tyrosine kinase inhibitors 1
Clinical Monitoring and Follow-up
- Response assessment should be based on improvement of mast cell activation symptoms and related organ damage 1
- Continue effective treatments for patients showing adequate response 1
- For inadequate response or loss of response, consider alternative or additional therapies 1