Variability of clinical manifestation of factor VII-deficiency in homozygous and heterozygous subjects of the European F7 gene mutation A294V

Inherited factor VII deficiency (FVIID) is a rare autosomal bleeding disorder. Subjects with reduced FVII activity and identified F7 gene mutation are registered in the International Greifswald registry of FVIID.1 The mutation A294V is the most frequent among 717 FVIID patients in Central and North-Eastern Europe. The high prevalence of FVIID homozygous and heterozygous subjects, who share the same mutation (A294V), offers the unique possibility to study the clinical variability in a relatively large number of individuals with the identical defect in the F7 gene. In the reported study we have analyzed the clinical variability of 14 homozygous and 99 heterozygous subjects with F7 gene mutation A294V. Subjects with combinations with other bleeding disorders such as von Willebrand Disease, deficiency of FIX, FII etc., were excluded.

We collected data on factor VII clotting (FVII:C) activity, FVII antigen (FVII:Ag), date of initial onset of bleeding and bleeding symptoms.1,2

FVII:C was assayed locally with standard one-stage methods using thromboplastin (mostly recombinant and human-derived, Thromborel S Dade Behring). FVII:Ag was measured at some of the centers using an immunoenzymatic method (Asserachrom, Diagnostica Stago, Asnieres, France). The following bleeding symptoms were evaluated according to published criteria:1–4 intracranial hemorrhage (ICH), gastrointestinal (GI) hemorrhage, hemarthrosis, subcutaneous hematoma as well as epistaxis, oral bleeding, and menorrhagia in accordance with Peyvandi and Mannucci.5 Endogenous thrombin potential (ETP) was measured in platelet poor plasma from controls and subjects homozygous for A294V in the presence of activated protein C.6 Citrated plasma samples from 8 control subjects without FV_Leiden or FVHR2 (factor V wild type; FV_wt) and without A294V mutation were used as a reference. We used the mutation H1299R as marker for FVHR2.7 The FV_Leiden mutation was determined according to Bertina et al.8

The 14 homozygous subjects for the F7 gene mutation A294V are characterized by mean levels of FVII:C of 10±6% and of FVII:Ag of 52±11%. Nine of the homozygous patients (64%) had spontaneous bleeding symptoms (classified as symptomatic) and 5 (36%) did not (classified as asymptomatic). There was no significant difference in FVII level between symptomatic and asymptomatic homozygous A294V subjects.

Table 1.Endogenous thrombin potential, bleeding symptoms and co-inheritance of FVHR2 in nine patients homozygous for the mutation A294V with available plasma samples.

The spontaneous bleeding profile of the 9 symptomatic subjects was characterized by GI (22%) bleeds, hemarthrosis (22%), epistaxis (33%), easy bruising (11%), gingival bleeding (22%), subcutaneous hematoma (11%), hematuria (22%), and menorrhagia (33%) but no ICH.

The thrombotic risk factor FV_Leiden has already been reported to have a moderating effect on bleeding symptoms in patients with severe deficiency of factors VIII (hemophilia A),9 factor IX (hemophilia B)10 or with the mutation FVII g.9726+5G>A (FVII_Lazio).11 We analyzed the presence of the thrombophilia risk factors FV_Leiden, FV_HR2 and FIIG20210A mutation in 14 patients homozygous for A294V. In 3 out of 5 asymptomatic cases (60%) we found a co-inheritance for FV_Leiden (heterozygous) or FV_HR2 (heterozygous and homozygous). Among 9 symptomatic homozygous patients 8 had neither FV_Leiden nor FV_HR2 or FIIG20210A and only one case with mild bleeding characterized by occasional hematomas was heterozygous for the FV_HR2 (p=0.09, Fisher exact test). These data suggest that the presence of FV_Leiden or FV_HR2 could attenuate the bleeding severity in homozygous A294V patients; however, due to the small size of patient population investigated, further studies are needed to clarify this. With a FV_HR2 allele frequency of 7.4% in the German population, the frequency of 5.5% FV_HR2 alleles among the symptomatic A294V patients matches the expected value, but the frequency of 30% FV_HR2 alleles among the asymptomatic cases is above the expected value for a random selection. The high frequency of FV_HR2 alleles suggests a moderating effect.

Recently we have shown an increased ETP in plasma samples from carriers of the mutations FV_Leiden or FVHR2.6 On the basis of these findings we studied the ETP in available plasma samples from 9 FVII deficient patients, homozygous for A294V (Table 1). The ETP values of all seven plasma samples of symptomatic patients were significantly (p=0.002, Student’s t-test) lower than the reference value. Increased ETP values were only observed in the two samples of asymptomatic individuals. The ETP study supports a possible modulating influence of FV_HR2 on differential clinical manifestations in homozygous A294V subjects. Further studies are required to confirm this trend.

This present study included 99 individuals heterozygous for A294V (52 males, mean age 33.4 years; 47 females, mean age 33.6 years). Their mean FVII level was 44±15%. Twenty-three (23%) and 76 (77%) heterozygous A294V carriers demonstrated or lacked spontaneous bleeding symptoms respectively. Nine of the 23 symptomatic heterozygous patients were sporadic cases; the others belonged to families (parents, siblings or children) of a FVII deficient index patient.

The FVII level did not differ significantly between symptomatic and asymptomatic heterozygous A294V subjects. The prevalence of FV_Leiden or FV_HR2 was similar among the symptomatic and asymptomatic heterozygous cases. The bleeding pattern of the 23 heterozygous patients consisted of epistaxis (65%), gum bleeds (17%), easy bruising (30%), hematoma (3%), and menorrhagia (56% in women older than 14 years), but hemarthrosis, ICH or GI bleeding were not observed. Three patients (Online Supplementary Table S2) were treated as needed with pdFVII (patients f.10 and 9) or tranexamic acid (pt. 4).

In previously published papers, heterozygous probands were usually characterized as clinically asymptomatic and only single cases of heterozygous patients with clinical manifestations have been described.2,4 For some mutations (Arg304Gln) heterozygous subjects have moderate bleeding symptoms;4,12 but systematic studies of heterozygous subjects for F7 gene mutations do not exist. Our large-scale analysis of A294V heterozygous subjects shows that the proportion of symptomatic carriers of FVIID is relatively high.

Footnotes

• ↵* Members of the International Greifswald Registry of FVII deficiency, see appendix.
• Funding: this work was partially supported by the German Federal Ministry for Education and Research (NBL3 program, reference 01 ZZ 0103). FH, KW, JA and SS are members of the IRF7, which is supported by Novo Nordisk.