F5 and Rare hereditary thrombophilia: Several other rare or recently identified mutations may contribute to inherited thrombophilia, including PC or PS dysfunctional variants, which are associated with functionally impaired proteins without quantitative deficiency; FV Cambridge and Liverpool variants, which confer APC resistance; and gain-of-function mutations in factors VII, X, and XI, which have been linked to familial VTE in rare reports but require further validation.