F8 and hemophilia: On the basis of residual FVIII:C, hemophilia is categorized in three main forms: severe (FVIII:C < 1 IU/dL), moderate (FVIII:C 1–5 IU/dL), and mild (FVIII:C 6–39 IU/dL) (Mannucci and Tuddenham 2001).