Venous thromboembolism associated with hyperhomocysteinemia, homozygosity for the methylenetetrahydrofolate reductase 677C>T gene variant, and secondary polycythemia.

: The development of pulmonary embolism/deep vein thrombosis (DVT) in the extremities is influenced by various risk factors. Hyperhomocysteinemia is one such risk factor, which may be associated with vitamin B12/folate deficiency, or the methylenetetrahydrofolate reductase gene variant, 677C>T. Here, we report a 47-year-old male who developed pulmonary embolism/DVT, associated with hyperhomocysteinemia (plasma homocysteine: 71.9 nmol/ml; reference range: 6.3-18.9 nmol/ml) and was homozygous (T/T) for the methylenetetrahydrofolate reductase variant. Serum levels of vitamin B12 and folate were within the normal range, while secondary polycythemia (hemoglobin: 18.2 g/dl and hematocrit: 50.8%) may have acted as an additional trigger for the thromboembolism. The pulmonary embolism/DVT was successfully managed and the patient has been doing well for longer than 3 years.