<h4>Background</h4>Phlegmasia cerulea dolens is a rare, life- and limb-threatening form of venous thrombosis that is often seen in the setting of hypercoagulable states or mechanical obstruction.<h4>Case report</h4>We report the case of a 49-year-old female with a history of multiple thromboembolic events and a methylenetetrahydrofolate reductase mutation who, despite therapeutic anticoagulation, developed phlegmasia cerulea dolens following renal transplantation. This evidence concerns the gene MTHFR and Venous thrombosis.