These include FV Leiden [49], Prothrombin G20210A mutation (which leads to a high prothrombin level) [50], high plasma homocysteine level [51], a mutation in the methylenetetrahydrofolate reductase gene 51, JAK2V617F mutations [52], and myeloproliferative neoplasms (MPN) [53]. The gene discussed is MTHFR; the disease is myeloproliferative disorder.