MRI: two had changes compatible with recent stroke Blood chemistry: one had positive antiphospholipid antibodies (IgG and IgS), positive antinuclear factor and lupus and lues antibodies; one had elevated fibrininogen, AT3, protein C, and low protein S and APC resistance, and was heterozygous for the factor V Leiden on gene testing. Here, F5 is linked to systemic lupus erythematosus.