Low prevalence of activated protein C resistance and coagulation factor V Arg506 to Gln mutation among Japanese patients with various forms of thrombosis, and normal individuals.

Resistance to activated protein C (APC), recently reported to be the most prevalent inherited cause of thrombosis among Caucasians, is associated with a single point mutation in the coagulation factor V gene. We investigated the prevalence of APC resistance and the factor V gene mutation (R506Q) in 34 consecutive Japanese patients with venous thrombosis or pulmonary thromboembolism and 63 control subjects. Three of the 33 patients examined (9%) had an APC ratio below the 5th percentile of control values (2.27), but all were above 2.0. The factor V mutation (R506Q) was not detected in the 29 patients studied, including the 3 patients whose APC ratios were below 2.27, or in 53 controls. In a tissue factor-based factor V assay to detect APC resistance recently described by Le et al. (Blood 1995;85:1704-1711), all patients studied were found to be normal including the three with a low APC ratio. We conclude that APC resistance and factor V gene mutation are less prevalent in Japan than in several European countries.