<s>[INST] <<SYS>> This is a medical question of type : causes <</SYS>> What causes Factor V deficiency ? [/INST] What causes factor V deficiency? Factor V deficiency is caused by mutations in the F5 gene that prevent the production of a functional factor V protein or decrease the amount of the protein in the bloodstream. Mutations are present in both copies of the F5 gene in each cell, which prevents blood from clotting normally. </s>