Duration of Short-Term Corticosteroid Burst for MCAS
For refractory MCAS symptoms requiring a corticosteroid burst, prescribe prednisone 0.5 mg/kg/day initially, followed by a slow taper over 1 to 3 months. 1
Specific Dosing Protocol
The American Academy of Allergy, Asthma, and Immunology provides clear guidance on corticosteroid burst duration for MCAS:
- Initial dose: 0.5 mg/kg/day of oral prednisone 1
- Taper duration: 1 to 3 months with slow, gradual reduction 1, 2, 3
- Indication: Reserved for refractory signs or symptoms not controlled by standard antimediator therapy 1
Procedural Prophylaxis Protocol
For patients requiring radiologic or invasive procedures where mast cell activation has been problematic, a different short-burst protocol applies:
- Dose: 50 mg prednisone administered at three specific time points 1
- Timing: 13 hours, 7 hours, and 1 hour before the procedure 1
- Purpose: Prevent perioperative mast cell activation events 1
Critical Limitations and Cautions
Corticosteroid side effects significantly limit enthusiasm for long-term use in MCAS. 1 The extended taper period (1-3 months) represents a balance between controlling severe symptoms and minimizing adverse effects including:
- Immunosuppression
- Metabolic disturbances
- Bone density loss
- Mood and cognitive changes
- Adrenal suppression with abrupt discontinuation
When Corticosteroid Bursts Are Appropriate
Steroid bursts should only be considered after optimizing first-line antimediator therapy:
- First-line therapy: Non-sedating H1 antihistamines at 2-4 times standard doses combined with H2 antihistamines 1, 4
- Second-line additions: Oral cromolyn sodium for gastrointestinal symptoms, leukotriene inhibitors for bronchospasm or GI symptoms 1
- Refractory cases only: When symptoms persist despite maximal antimediator therapy, then consider the 1-3 month steroid taper 1, 2
Common Pitfall to Avoid
Do not use short 5-7 day "burst and stop" protocols commonly employed for asthma or allergic reactions—MCAS requires the longer 1-3 month taper to adequately suppress mast cell activation while minimizing rebound symptoms upon discontinuation. 1 The extended taper allows time to optimize other antimediator therapies that will provide ongoing symptom control after corticosteroid withdrawal.