Characterization of patients with angioedema without wheals: the importance of F12 gene screening.

Sporadic and familiar forms of non-histaminergic angioedema and normal C1 inhibitor encompass a group of disorders possibly caused by bradikinin. We aimed to study the subgroups of hereditary angioedema with FXII mutation (FXII-HAE), unknown genetic defect (U-HAE) and idiopathic non-histaminergic acquired angioedema (InH-AAE). We screened the F12 locus in our cohort and delineated the clinical, laboratory and genetic features. Four families carried the p.Thr309Lys mutation in F12 gene. Haplotyping confirmed the hypothesis of a common founder. Six families were affected by U-HAE and 13 patients by sporadic InH-AAE. C4 levels were significantly lower in FXII-HAE than in InH-AAE. In the FXII-HAE group, none had attacks exclusively in high estrogenic states; acute attacks were treated with icatibant. Prophylaxis with tranexamic acid reduced the attack frequency in most patients. Our study provides new data on the diagnosis, clinical features and treatment of non-histaminergic angioedema, underlying the role of the screening for F12 mutations.