Pedigrees of families A and B. Probands are indicated by arrows. Family members who have experienced DVT and/or PE are shown as closed or half-closed symbols. Individuals with markedly elevated FVIII levels (FVIII:C >250%) are hatched, whereas carriers of the FV Leiden mutation (FVL) are indicated next to the symbols of family B. FVIII:C and FVIII antigen (FVIII:Ag) levels expressed in percentages are reported below each individual. Phased genotypes for the microsatellite markers located in introns (IVS) 1, 13, 22, and 25 of the F8 gene are also reported below each individual. Microsatellite alleles are identified by the respective PCR product sizes in bp. The haplotype shared by all family members with markedly elevated FVIII levels (140-187-130-81) is shown in red. Note that although the duplication is always associated with this haplotype, the reverse is not true, and several family members have inherited copies of the same haplotype without the duplication (shown in gray as all other haplotypes that are not associated with the duplication).