MTHFR and thrombophilia: The systematic approach demonstrated in this study, with short- and medium-term follow-up, shows that balloon dilation alone in endovascular therapy is a suitable treatment option for venous stenosis unrelated to hemodialysis therapy, but associated with the thrombophilia factor due to the methylenetetrahydrofolate reductase (MTHFR) 677 heterozygous mutation.