DIFFERENTIAL DIAGNOSIS
• Anaphylactoid reactions
• Carcinoid syndrome
• Globus hystericus
• Hereditary angioedema
• Pheochromocytoma
• Pseudoanaphylactic reaction: After injection of procaine penicillin. Is a drug effect of procaine and not a penicillin allergy.
• Scombroid poisoning: From ingestion of dark meat fish (e.g., tuna, mackerel, mahi-mahi). Histamine-like mediator - symptoms include flushing, sweating, nausea, vomiting, diarrhea, headache, palpitations, dizziness, rash, swelling of face and tongue, respiratory distress, vasodilatory shock.
• Serum sickness: Occurs several days after exposure to inciting agent
• Systemic mastocytosis: Benign or malignant
overgrowth of mast cells. Urticaria pigmentosa seen in benign form and the presence of reddish brown macular-papular cutaneous lesions which urticate after trauma - Darier’s sign.
• Vasovagal reactions: Bradycardia and hypotension without tachycardia, fl ushing, urticaria, angioedema, pruritus, and wheezing
• Pulmonary embolism, foreign body aspiration, arrhythmia
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CAUSES :
IgE mediated mast cell degranulation
. Complement activation (C3a, C4a, C5a) by antigenantibody complexes that contain complement fixing antibodies
. Other non-IgE dependent anaphylaxis-like syndromes may be caused by modulators of arachidonic acid metabolism, sulfi ting agents, exercise induced anaphylaxis, and idiopathic recurrent anaphylaxis
. Some important causes of anaphylaxis are:
. Antimicrobials (e.g., penicillin)
. Blood products (especially in IgA deficient patients)
. Diagnostic chemicals (iodinated contrast media)
. Ethylene oxide gas (dialysis tubing, other sterilized products)
. Exercise
. Foods (e.g., peanuts, nuts, fish, crustaceans, mollusks, cow milk, eggs, soybean most common)
. Immunotherapy
. Insect stings (e.g., honeybees, wasps, kissing bugs, deer flies)
. Latex rubber (gloves, catheters)
. Macromolecules (e.g., chymopapain, insulin, dextran, glucocorticoid, protamine)
. Vaccines
I Hypoxemia, hypercarbia, acidosis. Acidosis may cause apparent hyperkalemia by moving potassium extracellularly.
• Elevated serum and urine histamine (short-lived in circulation)
• Elevated serum tryptase, a mast cell enzyme marker for allergic and anaphylactic reactions. Peak level: 30-90 minutes after reaction onset.