The Importance of Complement Testing in Acquired Angioedema Related to Angiotensin-Converting Enzyme Inhibitors

Background Angiotensin-converting enzyme inhibitors may cause angioedema. Currently, no laboratory method is available for identifying acquired angioedema related to angiotensin-converting enzyme inhibitors. However, establishing the diagnosis is possible from the medical history and the preexisting angiotensin-converting enzyme inhibitor therapy, as well as by excluding other angioedema types. Objective To evaluate the results of complement testing in patients experiencing angioedema while taking angiotensin-converting enzyme inhibitors. Methods Between 2005 and 2019, a total of 149 patients taking angiotensin-converting enzyme inhibitors were referred to our Angioedema Center for the diagnostic evaluation of recurrent angioedema episodes. Complement measurement was performed on these patients. Results The mean age of the 149 patients treated with angiotensin-converting enzyme inhibitors at the onset of the index angioedema episode was 55.8 years. The mean interval between the introduction of angiotensin-converting enzyme inhibitor therapy and the occurrence of the initial symptoms of angioedema was 43 months. The most commonly used angiotensin-converting enzyme inhibitor was perindopril (32.9% of the patients). The initial angioedema episode involved the face in 50.3%, the lips in 40.9%, and the tongue in 33.5% of the patients. Angiotensin-converting enzyme inhibitors were discontinued in all 149 patients, and at the same time, a complement test was performed. The complement tests confirmed hereditary angioedema with C1-inhibitor deficiency in 2 patients and an additional 12 family members. Acquired angioedema with C1-inhibitor deficiency was found in 3 patients. Conclusions Excluding hereditary angioedema and acquired angioedema with C1-inhibitor deficiency is indispensable for establishing the diagnosis of acquired angioedema related to angiotensin-converting enzyme inhibitors.