Background: The purpose of this study was to compare the genetic background of superficial (SVT) and deep vein thrombosis (DVT).
Methods: Factor V (FV)-Leiden (G16891A)-, factor II(G20210A)-mutations, protein C- and S, as well as methylenetetrahydrofolate reductase (MTHFR) polymorphisms at C677T and A1298C, and serum homocysteine levels (hcy) were determined in 29 patients with SVT and 26 with DVT. Findings FV- and -II-mutations were less frequent in patients with SVT (2/3) compared with DVT (9/5), respectively (P < 0.002 in case of FV). However, the frequency of the MTHFR C677T polymorphism was significantly higher in patients with SVT compared with DVT (CT 12 versus 10, and TT 7 versus 1, respectively, P << 0.001). The distribution of the MTHFR A1298C genotype and serum hcy levels was similar in both patient groups. Protein S-deficiency was recorded once (SVT). Interpretation These results suggest that the MTHFR C677T-mutant genetically predisposes its carriers to SVT which may contribute to hypercoagulation in pre-existing varicose vein disease.