[Recurrent deep vein thrombosis and myeloproliferative syndrom: emergence of JAK2 mutation five years after the initial event]. / Thromboses veineuses à répétition et syndrome myéloprolifératif : positivité secondaire d'une mutation JAK2 cinq ans après l'événement initial.

JAK 2 mutation is the molecular event responsible for 95% of polycythemia cases and 50% of thrombocythemia vera and myelofibrosis cases. It can be used as a tool for the diagnosis of myeloproliferative disorders. We report a case illustrating the fact that a negative result does not definitively eliminate the diagnosis. A 40-year old woman, with a medical history of familial deep vein thrombosis, developed thrombosis of the inferior vena cava with extension to the suprahepatic veins and pulmonary embolism. No constitutional or acquired thrombophilia was diagnosed; search for JAK 2 mutation was negative. The patient was treated with fluindione. Five years later, she relapsed with popliteo-femoral and vena cava deep vein thrombosis. The etiological work-up included a PET scan which revealed diffuse uptake in bones and suspected neoplasic bone marrow invasion. Progenitor cell cultures were positive and JAK 2 mutation was confirmed. The bone marrow aspirate had the cytologic appearance of a myeloproliferative disorder. This case illustrates the fact that JAK 2 mutation can be identified several years after onset of a latent myeloproliferative disorder. Cases with a high clinical likelihood should lead to renewed search for this mutation. Secondary discovery of this mutation can be explained by a higher proportion of mutation expressing clones.