VWF and systemic lupus erythematosus: Remarkably, FVIII:C was lower than the VWF:Ag level, and the FVIII increase was lower than expected after administering FVIII/VWF concentrate, which appeared to be due to a lupus-like anticoagulant activity, with a prolonged APTT lupus and increasing levels of FVIII in serial dilution studies.