The importance of FV for normal haemostasis is highlighted by the bleeding diathesis associated with FV deficiency,7, 8, 9 as well as by the increased risk of deep vein thrombosis (DVT) caused by partial resistance to APC‐mediated proteolysis.10 Among the most common risk factors for DVT is the FVLeiden mutation (R506Q), which leads to diminished inactivation by APC.11 Another FV mutation, W1920R, termed FVNara, was recently associated with greater APC resistance than FVLeiden. This evidence concerns the gene F5 and deep vein thrombosis.