Summary
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.
Keywords
Bleeding score - factor VII deficiency - gene deletion - genotype - phenotype