FV and APC resistance: the plot thickens

In this issue of Blood, Nogami et al report on a novel factor V (FV) gene mutation (FV Trp1920?Arg, FVNara) associated with activated protein C (APC) resistance and a severe thrombotic phenotype in a young Japanese patient. Since the affected amino acid residue is located in the light chain of FV, far from the known APC-cleavage sites, this discovery may afford new insights into the molecular mechanisms of APC resistance.