What is the distinction between acquired angioedema type I and acquired angioedema type II due to C1 inhibitor deficiency?

Updated: May 20, 2020
  • Author: Amanda T Moon, MD; Chief Editor: William D James, MD  more...
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Answer

The distinction between acquired angioedema type I and acquired angioedema type II may be difficult to make at times, and it is imperative to stress that overlap does occur. For instance, cases of monoclonal gammopathy of undetermined significance (MGUS) have shown the monoclonal immunoglobulin itself to be the C1-INH antibody. Patients with acquired angioedema type I may initially present with autoantibodies to C1-INH, or the autoantibodies may develop as the disease progresses. While measuring antibodies against C1-INH is useful, groups have also developed assays that can measure the antibody against C1-INH in complex with C1-INH. In one study, anti–C1-INH antibodies were detected in 9 of 20 patients, while the complex between anti–C1-INH and C1-INH was found in 18 of 20, suggesting that there could be greater numbers of patients with anti–C1-INH antibodies than is seen when measuring antibody alone. [4]


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