JAK2 and Rare hereditary thrombophilia: Importantly, testing for thrombophilia including both inherited factors such as Factor V Leiden mutation, prothrombin gene mutation, and deficiencies of protein C, protein S, antithrombin, and acquired thrombophilic factors such as Janus kinase 2 v617F (JAK2) mutation, lupus anticoagulant, and cardiolipin antibodies is not expensive in relation to other diagnostic tests.