# Commonest inherited cause of thrombosis in Caucasians is:
a. Protein S deficiency
b. Factor V leiden mutation
c. Anti thrombin III deficiency
d. Protein C deficiency
The correct answer is B. Factor V Leiden mutation.
Factor V Leiden (G1691A or arg 506 glu substitution) and prothrombin
(G 20210 A) are rare in African and orientals but they have prevalence
in whites, highest prevalence of heterozygotes (11–14%) is reported in
Sweden and Arabs.