A follow‐up survey of patients with acquired angioedema due to C1‐inhibitor deficiency

Background Acquired angioedema due to C1‐inhibitor deficiency (C1‐INH‐AAE) is a rare form of bradykinin‐mediated angioedema. It is diagnosed by complement testing; its treatment consists of the management of angioedema (AE) attacks and of underlying disease. Objective Evaluate the results of the clinical follow‐up of patients with C1‐INH‐AAE. Methods Between 1999 and 2020, 3938 patients with angioedema were evaluated, and 17 diagnosed with acquired C1‐INH deficiency were followed‐up. Results Mean age of the 17 patients was 61 years at diagnosis. In 33%, ACE inhibitors provoked AE attacks. Autoantibodies against C1‐INH were detected in 10 patients at diagnosis and in a further patient during follow‐up. The AE attacks involved the skin in 70.6%, the upper airways in 41.2% and the tongue/lip in 52.9% of patients. Twelve of the 17 patients had an underlying condition, mainly (n = 11) lymphoproliferative disease. In 10 patients diagnosed with a haematological disorder, AAE symptoms preceded the onset of the latter. One patient has not experienced an AE attack since diagnosis. Twelve patients were treated for angioedema attacks, and 32% of the attacks required acute treatment. PdC1‐INH was used to relieve AE attacks, and rituximab for the treatment of underlying disease (in six patients). Six patients had multiple AE attacks before any treatment. The symptom‐free period increased in five patients after the on‐demand administration of pdC1‐INH concentrate and following treatment of the underlying disease in two patients. Conclusion Early diagnosis of C1‐INH‐AAE and underlying disease is indispensable to reduce disease burden by introducing appropriate, individualized treatment and regular follow‐up.