The following underlying disorders were present: monoclonal gammopathy of undetermined significance (47.7%), non-Hodgkin lymphoma (27.3%), anti-C1-INH autoantibodies alone (11.4%), and other conditions (4.5%).
The clinical picture and a previous history of non-Hodgkin lymphoma prompted us to rule out an acquired form of paraneoplastic, C1-inhibitor (C1-INH) deficiency: C1q and both antigen and functional C1-INH tested normal, whilst we found low plasma levels of C3 and C4 possibly related to the parallel detection of antiphospholipid antibodies.