Types of pseudoallergy

Q: 22 years old athletic basketball player with no past medical history is brought from college game after he developed a reaction to Non-steroidal Anti-inflammatory Drug (NSAID) during the game for ankle pain. Patient developed severe urticaria with angioedema. Patient has no known drug allergy (NKDA). Patient is successfully treated with epinephrine, nebs, H1-H2 combo, and steroids, and admitted to ICU for observation. Immunology service diagnosed him with pseudo-allergy. Patient probably had which type of Pseudoallergic reaction? (select one)

A) Type 1 

B) Type 2 

C) Type 3 

D) Type 4 

Answer: C

Although the classic four types of true allergic reactions are very well known, it is not much known that pseudoallergic reactions are also of four types. Some literature also accounts for Types 5 & 6. 

Whenever any reaction doesn't fit the classic IgE or IgG type reactions, they are called pseudoallergy. Aspirin and NSAIDs are most common to cause pseudoallergy. 

 

In contrast to true allergy types, pseudoallergy classification is based on clinical symptoms. NSAIDs are very well known to have such reactions:

Type 1 – asthma and rhinosinusitis

Type 2 – urticaria/angioedema

Type 3 – NSAID-induced urticaria/angioedema in an otherwise asymptomatic person

Type 4 – Blended (mixed respiratory and/or cutaneous) reactions in an otherwise asymptomatic person

#allergy

#pharmacology

References:

1. Stevenson DD, Sanchez-Borges M, Szczeklik A. Classification of allergic and pseudoallergic reactions to drugs that inhibit cyclooxygenase enzymes. Ann Allergy Asthma Immunol 2001; 87:177.

2. Waller DG. Allergy, pseudo-allergy and non-allergy. Br J Clin Pharmacol. 2011 May;71(5):637-8. doi: 10.1111/j.1365-2125.2011.03976.x. PMID: 21480945; PMCID: PMC3093068.

3. Zhang B, Li Q, Shi C, Zhang X. Drug-Induced Pseudoallergy: A Review of the Causes and Mechanisms. Pharmacology. 2018;101(1-2):104-110. doi: 10.1159/000479878. Epub 2017 Nov 15. PMID: 29136631.