Polyclonal autoantibodies against C1 inhibitor in a case of acquired angioedema

Angioedema Due to Acquired Deficiency of C1-Inhibitor: A Cohort Study in Spain and a Comparison With Other Series

BACKGROUND

Data on acquired angioedema due to C1-inhibitor deficiency (C1-INH-AAE) from 4 European countries (France, Italy, Germany, and Hungary) were recently published.

OBJECTIVE

To report data from a group of 50 patients with acquired C1-INH deficiency from Spain, of whom 46 had angioedema, and compare them with other European series.

METHODS

We performed a retrospective observational study of 46 patients with C1-INH-AAE and 4 asymptomatic patients. Clinical and biological characteristics and associated diseases were assessed and compared with other European series.

RESULTS

Women accounted for 73.9% of cases. The prevalence of C1-INH-AAE related to hereditary forms was 1/10.1. Overall, 8.7% patients were aged <40 years. Diagnostic delay was 1.1 years. Angioedema mainly affected the face (91.3%), followed by the oropharynx (63%), extremities (50%), and abdomen (37%). Only 1 patient underwent orotracheal intubation. Erythema marginatum was present in 1 patient. A hematologic disorder was recorded in 50% of patients. Angioedema preceded all benign conditions, mostly monoclonal gammopathy of undetermined significance, but appeared very close to or after malignant hematologic diseases (median, 2.2 and 0.29 years). Autoimmune diseases were associated in 50% (autoimmune thyroiditis, 21.5%; systemic lupus erythematosus, 10.9%). Half of them coexisted with hematologic disorders. Anti-C1-INH antibodies were found in 67% of tested patients and were not related to the associated disease. Long-term prophylaxis was necessary in 52.2%, most of whom responded to tranexamic acid.

CONCLUSIONS

This study emphasizes the possibility of C1-INH-AAE in patients younger than 40 and in autoimmune diseases other than systemic lupus erythematosus such as autoimmune thyroiditis.

The Immunopathology of Complement Proteins and Innate Immunity in Autoimmune Disease

The complement is a powerful cascade of the innate immunity and also acts as a bridge between innate and acquired immune defence. Complement activation can occur via three distinct pathways, the classical, alternative and lectin pathways, each resulting in the common terminal pathway. Complement activation results in the release of a range of biologically active molecules that significantly contribute to immune surveillance and tissue homeostasis. Several soluble and membrane-bound regulatory proteins restrict complement activation in order to prevent complement-mediated autologous damage, consumption and exacerbated inflammation. The crucial role of complement in the host homeostasis is illustrated by association of both complement deficiency and overactivation with severe and life-threatening diseases. Autoantibodies targeting complement components have been described to alter expression and/or function of target protein resulting in a dysregulation of the delicate equilibrium between activation and inhibition of complement. The spectrum of diseases associated with complement autoantibodies depends on which complement protein and activation pathway are targeted, ranging from autoimmune disorders to kidney and vascular diseases. Nevertheless, these autoantibodies have been identified as differential biomarkers for diagnosis or follow-up of disease only in a small number of clinical conditions. For some autoantibodies, a clear relationship with clinical manifestations has been identified, such as anti-C1q, anti-Factor H, anti-C1 Inhibitor antibodies and C3 nephritic factor. For other autoantibodies, the origin and the functional consequences still remain to be elucidated, questioning about the pathophysiological significance of these autoantibodies, such as anti-mannose binding lectin, anti-Factor I, anti-Factor B and anti-C3b antibodies. The detection of autoantibodies targeting complement components is performed in specialized laboratories; however, there is no consensus on detection methods and standardization of the assays is a real challenge. This review summarizes the current panorama of autoantibodies targeting complement recognition proteins of the classical and lectin pathways, associated proteases, convertases, regulators and terminal components, with an emphasis on autoantibodies clearly involved in clinical conditions.

Serum complexes between C1INH and C1INH autoantibodies for the diagnosis of acquired angioedema

Acquired angioedema due to C1-inhibitor (C1INH) deficiency (AAE) is caused by secondary C1INH deficiency leading to bradykinin-mediated angioedema episodes. AAE typically presents in adulthood and is associated with B cell lymphoproliferation. Anti-C1INH autoantibodies (antiC1INHAbs) are detectable in a subset of AAE cases and considered a hallmark of the disease. When free antiC1INHAbs and malignant tumors are not detectable, diagnosis relies on the finding of low C1INH levels and/or function, lack of family history and SERPING1 mutations, age at onset and low or undetectable C1q levels, none of which is specific for AAE. We tested the diagnostic value of a novel enzyme-linked immunosorbent assay (ELISA) for the detection of circulating complexes between C1INH and antiC1INHAbs (C1INH-antiC1INHAb) in the serum of 20 European AAE patients characterized on the basis of their complement levels and function. Free antiC1INHAbs were detected in nine of 20 patients [six of immunoglobulin (Ig)G class, two of IgM class and one simultaneously presenting IgG and IgM classes], whereas C1INH-antiC1INHAb complexes were found in 18 of 20 of the AAE cases, regardless of the presence or absence of detectable free anti-C1INHAbs. Of note, nine of 20 patients showed negative free antiC1INHabs, but positive C1INH-antiC1INHAb complexes in their first measurement. In the cohort presented, IgM-class C1INH-antiC1INHAb are specifically and strongly associated with low C1q serum levels. Detection of C1INH-antiC1-INHAbs provides an added value for AAE diagnosis, especially in those cases in whom no free anti-C1INH antibodies are detected. The link between IgM-class C1INH-antiC1INHAb complexes and C1q consumption could have further implications for the development of autoimmune manifestations in AAE.

Management of angioedema without urticaria in the emergency department

Angioedema refers to a localized, transient swelling of the deep skin layers or the upper respiratory or gastrointestinal mucosa. It develops as a result of mainly two different vasoactive peptides, histamine or bradykinin. Pathophysiology, as well as treatment, is different in each case; nevertheless, the resulting signs and symptoms may be similar and difficult to distinguish. Angioedema may occur at any location. When the affected area involves the upper respiratory tract, both forms of angioedema can lead to an imminent upper airway obstruction and a life-threatening emergency. Emergency physicians must have a basic understanding of the pathophysiology underlying this process. Angioedema evaluation in the emergency department (ED) should aim to distinguish between histamine- and bradykinin-induced angioedema, in order to provide appropriate treatment to patients. However, diagnostic methods are not available at the ED setting, neither to confirm one mechanism or the other, nor to identify a cause. For this reason, the management of angioedema should rely on clinical data depending on the particular features of the episode and the patient in each case. The history-taking should be addressed to identify a possible etiology or triggering agent, recording complete information for an ulterior diagnostic study in the outpatient clinic. It is mandatory quickly to recognize and treat a potential life-threatening upper airway obstruction or anaphylaxis. This review focuses on the underlying mechanisms and management of histamine- and bradykinin-induced angioedema at the emergency department and provides an update on the currently available treatments.

[Facial edema as an earlier presenting sign of giant cell arteritis. Possible relationship with angioedema]

Giant cell arteritis (GCA) is a chronic granulomatous vasculitis of unknown etiology occurring in the elderly. New-onset headache, scalp tenderness, jaw claudication, temporal artery abnormalities on physical examination, visual symptoms and associated polymyalgia rheumatica represent the most typical and frequent features of the disease. However, facial edema is being more commonly recognized as a presenting symptom that may herald the disease. We present a case with facial edema as initial symptom and discuss if this rare symptom of GCA is due to hereditary or acquired angioedema.

Autoimmune angioneurotic edema in a patient with Helicobacter pylori infection

Association of acquired autoimmune angioneurotic edema with other diseases is increasing. However, the precise mechanism by which antibodies to C1-esterase inhibitor (C1-INH) are produced, is not elucidated. We describe a patient with IgA antibodies against C1-INH without other autoimmune markers. Our patient had gastritis and Helicobacter pylori infection, proven by biopsy. This case suggests that H. pylori infection can act as triggering factor for acquired autoimmune angioneurotic edema.

Acquired deficiency of the inhibitor of the first complement component: presentation, diagnosis, course, and conventional management

Acquired deficiency of the inhibitor of the first complement component (C1-INH) is a rare, potentially life-threatening disease whose cause, course, and management are not completely defined. This article analyzes the etiopathogenetic mechanism, the clinical presentation, and the relationship between acquired C1-INH deficiency and lymphoproliferative disorders. Moreover, the authors give an overview of the outcome of the disease and the different therapies proposed to cure it.

Autoantibodies and lymphoproliferative diseases in acquired C1-inhibitor deficiencies

Angioedema due to acquired C1-inhibitor (C1-INH) deficiency (also referred to as "acquired angioedema") is a rare, life-threatening disease with poorly defined etiology, therapy, and prognosis. To define the profile of acquired C1-INH deficiency and to facilitate the clinical approach to these patients, we report on 23 patients with acquired C1-INH deficiency followed for up to 24 years (median, 8 yr), and review the literature. We measured C1-INH activity with chromogenic assay and detected autoantibodies to C1-INH by enzyme-linked immunosorbent assay (ELISA). Median age at onset of angioedema was 57 years (range, 39-75 yr). All patients had C1-INH function and C4 antigen below 50% of normal. C1q was reduced in 17 patients. Autoantibodies to C1-INH were present in 17 patients. Long-term prophylaxis of attacks with danazol was effective in 2 of 6 patients, and with tranexamic acid, in 12 of 13 patients. Therapy with C1-INH plasma concentrate was necessary in 12 patients: 9 had rapid positive response and 3 became progressively resistant. Associated diseases at the last follow-up were non-Hodgkin lymphomas (3 patients), chronic lymphocytic leukemia (1 patient), breast cancer (1 patient), monoclonal gammopathies of uncertain significance (13 patients). In 4 patients no pathologic condition could be demonstrated. Compared with the general population, patients with acquired C1-INH deficiency present higher risk for B-cell malignancies, but not for progression of monoclonal gammopathies of uncertain significance to malignancy. Antifibrinolytic agents are more effective than attenuated androgens in long-term prophylaxis. Patients with acquired C1-INH deficiency may be resistant to replacement therapy with C1-INH plasma concentrate.