Endothelial cell activation during edematous attacks of hereditary angioedema types I and II.

BACKGROUND: Hereditary angioedema (HAE) caused by C1-inhibitor (C1-INH) deficiency (HAE-C1-INH) is a potentially life-threatening rare disease caused by the decreased activity of C1-INH. Lack of C1-INH leads to overproduction of bradykinin, a potent vasoactive peptide. Although angioedema is induced by bradykinin, the function and activation of endothelial cells (ECs), the targets of bradykinin, have not yet been studied during HAE attacks. OBJECTIVE: We studied whether EC function is altered during HAE attacks in comparison with attack-free intervals. METHODS: Forty-six consecutive samples obtained during attacks from 18 patients with HAE-C1-INH were compared with inter-attack samples of the same patients. The patients' sera were tested for von Willebrand factor (VWF) antigen, VWF collagen-binding activity, soluble E-selectin, and endothelin-1 levels by using ELISA and BRAHMS Kryptor technologies. RESULTS: Levels of all 4 EC markers (VWF antigen, VWF collagen-binding activity, soluble E-selectin, and endothelin-1) were significantly increased during HAE attacks. Their increases were even more obvious in the subgroup of patients without any pre-existing risk factors for endothelial dysfunction. CONCLUSION: In this study we demonstrated that ECs are activated during HAE attacks. Our results might suggest the need for revising the knowledge on the pathogenesis of HAE-C1-INH and for reconsidering the role of ECs as a possible novel therapeutic target in patients with this disease.

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.