Predisposing factors are liver cirrhosis, myeloproliferative neoplasms, liver and pancreatic malignancies, factor V Leiden mutation, protein C or protein S deficiency, microparticles, JAK2V617F mutation, and methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms. This evidence concerns the gene MTHFR and myeloproliferative neoplasm.