Management of Mast Cell Activation Syndrome

First-Line Symptomatic Management

The American Academy of Allergy, Asthma, and Immunology recommends treatment with H1 and H2 antihistamines as first-line therapy for patients with elevated tryptase experiencing symptoms of mast cell activation, with cromolyn sodium for gastrointestinal and neurologic symptoms, and immediate intramuscular epinephrine for any acute systemic reactions involving two or more organ systems 1, 2, 3
Combined H1 and H2 antihistamines are superior to either agent alone for controlling mast cell mediator-related symptoms, according to the National Comprehensive Cancer Network 2, 3
H1 antihistamines address urticaria, pruritus, and flushing, while H2 blockers provide additional benefit for gastrointestinal symptoms and cardiovascular manifestations 2, 3, 4

The American Heart Association recommends aggressive fluid resuscitation with normal saline or lactated Ringer's solution at 5-10 mL/kg boluses for hypotension, tachycardia, syncope, or near-syncope 3
The American Academy of Allergy, Asthma, and Immunology suggests that these symptoms indicate systemic anaphylaxis when occurring with involvement of at least one other organ system 1, 3
Urticaria, pruritus, flushing, and angioedema respond to H1 antihistamines, according to the American Academy of Dermatology 1
Topical cromolyn sodium is effective for localized cutaneous flares, as recommended by the National Comprehensive Cancer Network 2

The American Heart Association recommends intramuscular epinephrine 0.3-0.5 mg as first-line treatment for anaphylaxis, with no absolute contraindications 4, 3
The National Comprehensive Cancer Network suggests administering epinephrine immediately when anaphylaxis involves hypotension, laryngeal edema, vasomotor collapse, oxygen desaturation, or seizures 2
Multiple doses of epinephrine may be required for severe hypotension or bronchospasm, according to the American Academy of Allergy, Asthma, and Immunology 4

The American Academy of Allergy, Asthma, and Immunology recommends systematic evaluation to identify specific triggers for each patient, with avoidance strategies tailored to identified triggers 1, 3
Common triggers include hot water, alcohol, certain drugs, stress, exercise, hormonal fluctuations, infection, and physical stimuli such as pressure or friction, according to the National Comprehensive Cancer Network 1, 3

The American Academy of Allergy, Asthma, and Immunology suggests obtaining serum tryptase during acute episodes, with initial sample as soon as feasible, second at 1-2 hours after symptom onset, and third at 24 hours or in convalescence 4, 5, 3
Acute elevation >20% + 2 μg/L above baseline on at least 2 separate occasions is diagnostic of mast cell activation syndrome, according to the American Academy of Allergy, Asthma, and Immunology 1, 3

The American Academy of Allergy, Asthma, and Immunology recommends that all patients with elevated tryptase and mast cell activation symptoms carry two epinephrine auto-injectors at all times, with training on proper administration technique 3, 6
The National Comprehensive Cancer Network suggests prescribing appropriate dose: >12 years 500 μg IM, 6-12 years 300 μg IM, <6 years 150 μg IM 4

The American Heart Association notes that concomitant cardiovascular disease, β-blockers, or ACE inhibitors increase anaphylaxis risk and severity, and these medications should be reviewed with cardiology before continuation 2, 3
The American Academy of Allergy, Asthma, and Immunology suggests that persistent symptoms suggest alternative diagnoses such as chronic urticaria or poorly controlled asthma rather than mast cell activation syndrome 1
The diagnosis requires episodic symptoms affecting at least 2 organ systems concurrently, with documented mediator elevation during acute episodes and response to therapy, according to the American Academy of Allergy, Asthma, and Immunology 1