A Multicentre UK-Based Audit on Acquired C1 Inhibitor Deficiency 2021

Acquired angioedema due to C1 inhibitor deficiency (C1-INH-AAE) is a very rare disease compared to Hereditary angioedema (HAE). There is a need for an updated characterisation of patients with C1-INH-AAE to understand the disease pathogenesis and optimise treatment. We describe the disease burden, long term prophylaxis (LTP) and C1-INH-AAE-associated diseases in a multicentre UK cohort. Data on C1-INH-AAE patients were collected using a standardised proforma. 12 UK centres have responded to date. Further data collection is in progress. Data on 40 C1-INH-AAE patients were reported. 52% (21/40) patients were females with an average age at diagnosis of 63 years. The delay in diagnosis was 1.9 years. The average frequency of angioedema attacks was 7/year with 2/7 severe attacks. 23/40 patients were on LTP: 5/23 were on attenuated androgens and 16/23 on anti-fibrinolytic drugs with comparable efficacy 5/5 and 15/16, respectively. 2/23 patients were on additional prophylaxis, including C1-INH. 30/40 patients had identified associated diseases with a predominance of clonal B cell disorders in 27/30. 15/27 patients had Non-Hodgkin lymphoma: mostly splenic marginal zone lymphoma 11/15, 6/27 had MGUS, 4/27 CLL, 1/27 Waldenstrom’s macroglobulinemia (WM) and 1/27 had a non-malignant B cell clone. 1/40 had mixed connective tissue disease and 2/40 had rheumatoid arthritis. 9/9 of C1-INH-AAE patients improved within a year of treating the underlying B cell disorder. Most C1-INH-AAE patients in the UK had an underlying clonal B cell disorder with good remssion of AAE after treatment. Tranexamic acid was the predominant LTP, albeit androgens were effective also.