FACTOR VIIA IN PATIENTS WITH C1-INHIBITOR DEFICIENCY

In hereditary angioedema (HAE), normal C1-inhibitor (C1-INH) is low an d the contact system activated. Recently, the findings of a tissue fac tor mutant selectively deficient in promoting the conversion of FVII t o FVIIa, but with retained cofactor for FVIIa, made it possible to exa mine reliably the pre-existing content of FVIIa in HAE patients. This was of interest as FXIIa (mainly inhibited by C1-INH) is able to activ ate FVII directly. FVIIa in 21 remission HAE patients were within norm al limits but nearly doubled as compared to their 23 normal siblings ( p = 0.0017). Cold promoted activation of FVII (CPA) (common clot assay ) was displayed in plasma of all 5 untreated patients (C1-INH function <35%), but not in plasma of 2 patients treated prophylactically with danazol (C1-INH function about 40%). These results suggest that there is a minute, yet significant activation of FVII in patients with C1-IN H deficiency.