I had a conversation with a colleague who mentioned they were seeing decreased factor XII activity and antigen levels during sickle cell crisis. I found two references on reduced contact factors in sickle cell: Gordon EM, Klein BL, Berman BW, et al. Reduction of contact factors in sickle cell disease. J Pediatr 1985; 106:427-30, and Miller RL, Verma PS, Adams RG. Studies of the kallikrein-kinin system in patients with sickle cell anemia. J Natl Med Assoc 1983; 75 :551-6. Nothing more recent. My Colman text refers to contact factors’ interactions with inflammatory pathways and with fibrinolysis, implying consumption. Has anyone ever heard of reduced factor XII in sickle cell anemia or during sickle cell crisis? Geo.