doi:10.11613/BM.2014.018engIzquierdo Alvarez, SilviaBarrio Ollero, Eva MaríaLlinares, FMLorente, FCalvo Martin, M TeresaA deep vein thrombosis caused by 20209C>T mutation in homozygosis of the prothrombin gene in a Caucasian patientART-2014-81191Introduction: Additional nucleotide substitutions in the 3 ´-untranslated region of prothrombin gene could explain some thrombotic events and also adverse pregnancy outcomes. We describe the first case of a homozygous 20209C>T mutation as the cause of deep vein thrombosis in a Spanish patient. Case and methods: The 56-year-old male patient with a partial tear of the Achilles tendon developed calf (tibial) deep vein thrombosis after im- mobilization and was treated with an anticoagulant. To determine if the deep vein thrombosis was of genetic origin, a peripheral blood DNA sample was analysed for the presence of the three most frequent mutations associated with thrombotic events: factor V Leiden (1691G>A), prothrombin (20210G>A) and methylene tetrahydrofolate reductase (677C>T). The presence or absence of the normal allele of prothrombin could not be deter- mined using the PTH-FV-MTHFR StripAssay (Vienna Lab). Results: Comprehensive analysis showed that the patient had a variant interfering with the polymerase chain reaction product, we sequenced the entire prothrombin gene and found that the patient had a homozygous C>T mutation at position 20209; this interfered with the polymerase chain reaction product, which needs a C at this position to be able to bind to the wild-type probe present in the test strip. Conclusion: The homozygous 20209C>T mutation and the presence of the mutation 677C>T in heterozygosity explained the patient’s deep vein thrombosis because the combination of mutations would increase the risk of thrombosis. Suitable genetic counselling should be provided to the pa- tient and first-degree relatives as it important to detect prothrombin gene variants that could increase risk for thrombotic events.2014http://zaguan.unizar.es/record/3246210.11613/BM.2014.018http://zaguan.unizar.es/record/32462oai:zaguan.unizar.es:32462Biochemia Medica 24, 1 (2014), 159-166by-nc-ndhttp://creativecommons.org/licenses/by-nc-nd/3.0/es/info:eu-repo/semantics/openAccess