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The role of C1 inhibitor and complement as acute phase reactants: are we missing the diagnosis of hereditary angioedema? Stepaniuk, Peter; Bosonea, Ana-Maria; Pourshahnazari, Persia; Roos, Adrienne; Kanani, Amin

Abstract

Background C1 inhibitor (C1-INH) and complement 4 (C4) have historically been referred to as positive acute phase reactants, however this has never been evaluated in hereditary angioedema (HAE) patients. Low function of C1-INH and low levels of C4 are important in the diagnosis of HAE type 1 and 2. If C1-INH and/or C4 are significant acute phase reactants, their levels may be falsely “normal” in patients with HAE when measured during times of infection or inflammation resulting in missed or delayed diagnosis. Case presentation We present a case series of four HAE patients who had C4, C1-INH, c-reactive protein (CRP) and ferritin measured at baseline and again during a self-reported upper respiratory tract infection (URTI) or flu-like illness. We did not identify any HAE patients who had a significant change in their C1-INH functional level in the context of a mild infection. However, the C4 level did increase into the normal range on three occasions (2 patients, with 1 patient having elevation during two separate illnesses). Conclusions C1 inhibitor may not be a clinically significant acute phase protein and appears to still be a reliable diagnostic marker of hereditary angioedema, even in times of modest acute inflammation, unlike complement C4 which can be elevated in this setting.

Item Metadata

Title
The role of C1 inhibitor and complement as acute phase reactants: are we missing the diagnosis of hereditary angioedema?
Creator
Stepaniuk, Peter; Bosonea, Ana-Maria; Pourshahnazari, Persia; Roos, Adrienne; Kanani, Amin
Publisher
BioMed Central
Date Issued
2021-10-09
Description
Background C1 inhibitor (C1-INH) and complement 4 (C4) have historically been referred to as positive acute phase reactants, however this has never been evaluated in hereditary angioedema (HAE) patients. Low function of C1-INH and low levels of C4 are important in the diagnosis of HAE type 1 and 2. If C1-INH and/or C4 are significant acute phase reactants, their levels may be falsely “normal” in patients with HAE when measured during times of infection or inflammation resulting in missed or delayed diagnosis. Case presentation We present a case series of four HAE patients who had C4, C1-INH, c-reactive protein (CRP) and ferritin measured at baseline and again during a self-reported upper respiratory tract infection (URTI) or flu-like illness. We did not identify any HAE patients who had a significant change in their C1-INH functional level in the context of a mild infection. However, the C4 level did increase into the normal range on three occasions (2 patients, with 1 patient having elevation during two separate illnesses). Conclusions C1 inhibitor may not be a clinically significant acute phase protein and appears to still be a reliable diagnostic marker of hereditary angioedema, even in times of modest acute inflammation, unlike complement C4 which can be elevated in this setting.
Subject
Hereditary angioedema; Acute phase; C1 inhibitor; C4; Reactant; Infection; Illness; CRP; Complement
Genre
Article
Type
Text
Language
eng
Date Available
2021-11-09
Provider
Vancouver : University of British Columbia Library
Rights
Attribution 4.0 International (CC BY 4.0)
DOI
10.14288/1.0403347
URI
http://hdl.handle.net/2429/80169
Affiliation
Medicine, Faculty of; Non UBC; Medicine, Department of
Citation
Allergy, Asthma & Clinical Immunology. 2021 Oct 09;17(1):103
Publisher DOI
10.1186/s13223-021-00607-5
Peer Review Status
Reviewed
Scholarly Level
Faculty
Copyright Holder
The Author(s)
Rights URI
http://creativecommons.org/licenses/by/4.0/
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Attribution 4.0 International (CC BY 4.0)