SERPINC1 and antiphospholipid syndrome: After admission at the age of 17, blood tests showed slightly low activity of antithrombin III (61%) and protein C (63%), and the presence of congenital coagulopathy was suspected, although genetic testing for SERPINC1 and PROC were negative. In addition, there was no evidence of antiphospholipid antibody syndrome or hyper-homocystinemia, which could cause juvenile cerebral infarction.