LOW-PREVALENCE OF ACTIVATED PROTEIN-C RESISTANCE AND COAGULATION-FACTOR-V ARG(506) 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 m ost prevalent inherited cause of thrombosis among Caucasians, is assoc iated with a single point mutation in the coagulation factor V gene. W e investigated the prevalence of APC resistance and the factor V gene mutation (R506Q) in 34 consecutive Japanese patients with venous throm bosis or pulmonary thromboembolism and 63 control subjects. Three of t he 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 mutati on (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 t issue factor-based factor V assay to detect APC resistance recently de scribed by Le et al. (Blood 1995;85:1704-1711), all patients studied w ere found to be normal including the three with a low APC ratio. We co nclude that APC resistance and factor V gene mutation are less prevale nt in Japan than in several European countries.