To investigate the clinical significance of anti-factor XII (FXII) in a large cohort of patients with systemic lupus erythematosus (SLE).
This study comprised 127 patients with SLE. IgG and IgM anti-FXII were tested by an in-house ELISA. 123 healthy donors comprised the control group.
51 (40%) patients with SLE and 9 (7%) healthy controls were positive for anti-FXII. IgG and IgM anti-FXII were frequently found in patients with thrombosis (28% and 13%, respectively). Levels of IgG and IgM anti-FXII were higher in patients with thrombosis than in the control group (p<0.001 and p=0.005, respectively). Anti-FXII was more frequent in patients with arterial thrombosis (31% vs 4% for IgG and 14% vs 3% for IgM, respectively) and venous thrombosis than in controls (37% vs 4% for IgG). IgG anti-FXII were more frequent in patients with miscarriages and fetal death (35% and 40% vs 4% for IgM). The prevalence of IgM anti-FXII was not different between groups.
Anti-FXII are frequent in patients with SLE. Their presence is associated with thrombosis and adverse obstetric history, making these antibodies a novel marker for the antiphospholipid syndrome.