Summary
High FVIII:C levels have previously been shown to be an independent risk factor for
thrombosis with 4.8 times higher potential risk of thrombosis in individuals with
FVIII:C levels greater than 1.5 u/ml. Recently, we found that raised FVIII:C levels
are largely attributable to elevated FVIII:Ag levels. The determinants of FVIII:Ag
levels are unclear and might be partly genetic. The promoter of the F8 gene has recently been characterised we therefore investigated the promoter and the
3’ terminus of the F8 gene for possible polymorphisms associated with raised FVIII:Ag levels in 62 selected
individuals with a thrombotic tendency. We confirm previous reports that raised FVIII:C
levels are largely attributable to an elevation in FVIII:Ag and this is also associated
with elevation of vWF; non-O blood group; relatively short APTT and relatively low
APC ratio. We screened 1140bp of the proximal promoter including the protein binding
sites identified by DNase I footprint analysis by SSCP, however no polymorphisms were
identified. Direct DNA sequence analysis of the region –542 to +165 failed to identify
any sequence polymorphisms. The recently described polymorphism in the polyadenylation
cleavage site in the prothrombin gene associated with increased prothrombin activity
prompted us to screen the region surrounding the 3’ terminus of the F8 gene for polymorphisms but we found none.