F7 gene variants modulate protein levels in a large cohort of patients with factor VII deficiency: Results from a genotype-phenotype study

Congenital factor VII (FVII) deficiency is a rare bleeding disorder caused by mutations in F7 gene with autosomal recessive inheritance. A clinical heterogeneity with poor correlation with FVII:C levels has been described. It was the objective of this study to identify genetic defects and to evaluate their relationships with phenotype in a large cohort of patients with FVII:C<50 %. One hundred twenty-three probands were genotyped for F7 mutations and three polymorphic variants and classified according to recently published clinical scores. Forty out of 123 patients (33 %) were symptomatic (43 bleedings). A severe bleeding tendency was observed only in patients with FVII:C<0.10 %. Epistaxis (11 %) and menorrhagia (32 % of females in fertile age) were the most frequent bleedings. Molecular analysis detected 48 mutations, 20 not reported in the F7 international databases. Most mutations (62 %) were missense, large deletions were 6.2 %. Compound heterozygotes/homozygotes for mutations presented lower FVII:C levels compared to the other classes (Chi2=43.709, p<0,001). The polymorphisms distribution was significantly different among the three F7 genotypic groups (Chi2=72.289, p<0,001). The presence of truncating mutations was associated with lowest FVII:C levels (Chi2=21.351, p=0.002). This study confirms the clinical and molecular variability of the disease and the type of symptoms. It shows a good correlation between the type of F7 mutation and/or polymorphisms and FVII:C levels, without a direct link between FVII:C and bleeding tendency. The results suggest that large deletions are underestimated and that they represent a common mechanism of F7 gene inactivation which should always be investigated in the diagnostic testing for FVII deficiency

Blood Group O Protects against Inhibitor Development in Severe Hemophilia A Patients

Increasing evidence supports the link between ABO(H) blood group determinants and hemostasis. In particular, the ABO-related different glycosylation patterns of von Willebrand factor strongly influence its clearance and functional levels, and this may contribute to the inter-individual variations in the half-life of infused Factor VIII (FVIII) in hemophilia A (HA) patients. We investigated the role of ABO blood groups in regulating FVIII immunogenicity by evaluating their distribution in patients with severe (FVIII < 1 IU/dL) HA according to inhibitor development and other known relevant factors. In a cohort of Italian severe HA patients (n = 209), the ABO blood group distribution was similar to that in the healthy general population. However, the distribution of inhibitors, developed in 56 patients overall (26.8%), was significantly different in the four ABO phenotypes (O, 18.2%; A, 31.9%; B, 39.1%, AB, 25%; p = 0.033); this difference seemed more pronounced when only high-titer inhibitors (overall, 21.1%) were considered (O, 11.4%; A, 27.7%; B, 34.8%; p = 0.011). Relative risks in O versus non-O blood group were 0.55 (95% CI: 0.33-0.92) and 0.40 (95% CI: 0.21-0.77) for any and high-titer inhibitors, respectively. In a multivariate logistic regression, O blood group was shown to lower (approximately twofold) inhibitor risk, similarly with plasma-derived FVIII, whereas high-risk F8 mutations were associated with increased risk. However, the estimated effect of O blood type on inhibitor development was free from any significant correlation to other covariates, including presence of high-risk F8 mutations and type of replacement FVIII used. In this retrospective cohort of severe hemophiliacs, blood group O appears to protect against inhibitor development, with independent effects from other covariates. Larger prospective studies are needed to confirm this finding and to delve deeper into its pathophysiologic mechanisms