This patient has the acquired form of angioedema, a syndrome often associated with malignancies such as chronic lymphocytic leukemia and B-cell lymphoma and gammopathies such as Waldenstrom's macroglobulinemia. The disorder is due to "consumption" or hypercatabolism of the inhibitor of C1 (C1 INH) by autoantibodies that impair the function of C1 INH.
In contrast, to the acquired form of angioedema, the hereditary form is usually due to decreased synthesis of C1 INH, or in about 10% of cases due to production of a mutated nonfunctional C1 INH.
The two syndromes are distinquished by measuring C1 proteins such as C1q; patients with acquired angioedema have low or undetectable serum concentrations of C1q, while patients with hereditary angioedema have normal serum C1q.
Both groups of patients hve low concentrations of C4 and CH50. C3 values are usually normal. The serum protein electrophoresis may show a monoclonal spike, but this finding is not diagnostic for either form of angioedema.