A novel mutation in exon 8 of C 1 inhibitor ( C 1 INH ) gene leads to abolish its physiological stop codon in a large C hinese family with hereditary angioedema type I

C1 inhibitor ( C 1 INH ) plays an important role in the classical pathway of the complement system. Mutations in C 1 INH gene cause quantitative or qualitative deficiencies in C 1 INH , which can lead to hereditary angioedema ( HAE ) type I or II . Here, we identified a novel frame‐shift mutation c.1391‐1445del55 (p.v464fsx556) in exon 8 in a large C hinese family with HAE type I. This 55 base pairs deletion abolishes the original stop codon and introduces a new stop codon 220 bp downstream of the original one, and leads to mutated C 1 INH protein prolonged from 500 to 556 amino acids. The levels of C 4 and C 1 INH as well as C1 INH activity in serum were significantly reduced in affected individuals. This is the first report of a novel mutation abolishing the physiological stop codon of C1 INH gene in a large C hinese family with HAE type I.