Novel duplication in the F12 gene in a patient with recurrent angioedema.

Edema formation is mediated by histamine or bradykinin release and may have several hereditary and acquired causes. In hereditary forms of bradykinin-mediated angioedemas, mutations in the genes encoding C1-inhibitor (SERPING1) as well as coagulation factor XII (F12) have been described. We present a novel F12 gene mutation, a duplication of 18 base pairs (c.892_909dup) in a 37-year-old woman with recurrent angioedema and normal C1-inhibitor level. A single episode of facial edema in the family of the patient showed co-segregation with the mutation. This duplication is causing the repeated presence of 6 amino acids (p.298-303) in the same region of factor XII, as those three mutations described previously in cases of hereditary angioedema with normal C1-INH function. These results may confirm the importance of the proline-rich region of factor XII protein in edema formation.