Hereditary angioedema: Report of a large kindred with a rare genetic variant of C1‐esterase inhibitor

The hereditary angioedema syndrome (HAE) is attributed to deficiency of an a2-glycoprotein which inhibits the activated first component of complement (Cl). This protein is also called C1 esterase inhibitor (C? INH). The disease seems to be transmitted as an autosomal dominant trait. Two variants of the disease have been described: both have a low level of C? INH activity, but in one of them a non-functional C? INH can be detected in the serum. The family reported belongs to this last type. All affected members had the typical abnormalities of the complement system, namely a low level of active C? INH and a decreased amount of C4 and of total hemolytic complement. The presence of non-functional C? INH was revealed by an immunochemical assay. The antigenic determinants of the inactive protein we have studied do not differ from those of the normal one. However, the electrophoretic mobilmities of the two proteins were slightly different inasmuch as the pathological protein migrated more slowly. This protein may be a new variant of C INH.