Clinical Research: Treatment with Warfarin Followed By Hydroxyurea for Thrombosis Caused By JAK2^V617F-Positive Essential Thrombocythemia Associated with Mutation in the Thrombomodulin Gene and Deficiency of Protein S

JAK2^V617F-positive essential thrombocythemia is rarely associated with mutation in the thrombomodulin gene and deficiency of protein S without being reported in the literature. A case of a previously healthy 50-year-old Chinese female presenting with superior mesenteric vein thrombosis and portal thrombosis showed by enhanced computed tomography(CT) scan is reported. Blood platelet count showed 644×10⁹/L. Molecular testing for genetic mutation found a JAK2^V617F mutation by 11089 copies per 100ng DNA revealed by real-time polymerase chain reaction (RT-PCR), with the mutation rate being over ten percent. Level of free protein S decreased to 30.4%(reference:70%-140%). Heterozygous missense mutation(c.404C>G, i.e.nucleotide 404 of encoding region was mutated from cytosine to guanine) in exon 1 in the thrombomodulin gene was detected in peripheral blood, which caused p.Pro135Arg(i.e.amino acid No.135 was changed from proline to arginine). The chromosomal position of thrombomodulin gene was at chr20:23029738. Family investigation showed that a similar mutation in the thrombomodulin gene was detected in peripheral blood in her daughter. Low molecular weight heparin was given at the beginning of treatment, and bleeding was monitored. In the meantime, warfarin was administered orally and the dosage of which was adjusted to maintain the international normalized ratio of prothrombin time at the range of 2 to 3. Adjust the dosage of hydroxyurea according to blood cell count. A month later, no new thrombosis was found in enhanced CT scan. It was an amazing feat that the patient was in a state of remission without new thrombosis being found for a year. JAK2^V617F-positive essential thrombocythemia with mutation in the thrombomodulin gene and deficiency of protein S tends to be incurable. Warfarin alone with hydroxyurea may serve as an effective option to those cases.