Acquired angioedema with C1 inhibitor deficiency: Is the distinction between type I and type II still relevant?

Background: Acquired angioedemas are divided into type I associated with ly mphoproliferation and type II caused by anti-C1-inhibitor antibodies. Recen t reports have suggested that this distinction is not so clear-cut, mainly because of the presence of antibodies against the C1 inhibitor in some case s belonging to the type I group. We report herein 2 additional cases of acq uired angioedema with anti-C1-inhibitor antibody. Material and Methods: One man and 1 woman had had acquired angioedema for several years. In the man, a monoclonal component had been detected several years before the present study. In the second patient, a monoclonal component was detected during th e study. The following data were studied on successive blood samples collec ted during angioedema manifestations: complement component levels, function al activity of the classical pathway, functional and antigenic C1 inhibitor doses, ELISA test to detect autoantibodies to C1 inhibitor and Western blo t analysis of the C1 inhibitor. Results: In both patients, CH50 and C4 acti vities were decreased, and an autoantibody to C1 inhibitor was detected. In 1 case, the antibody appeared after the monoclonal component; in the secon d case, it appeared before and belonged to a different immunoglobulin class . Conclusion: Our data suggest that the distinction between type I and type II acquired angioedema is no longer valid because of overlapping in some c ases.