JAK2 V617F-positive essential thrombocythemia in a patient with Klinefelter syndrome: a case report.

Klinefelter syndrome (KS) is the most commonly diagnosed X chromosome aneuploid syndrome among males. The association between hematologic malignancies such as non-Hodgkin lymphoma and leukemia and KS has been established recently on the basis of numerous case reports and a large cohort study. The risk of chronic myeloproliferative disease (MPD) as a hematologic malignancy in KS, however, has not been evaluated to date. Moreover, to our knowledge, there is only one case report that observed MPD in a patient with KS. Even though the Janus kinase 2 (JAK2) mutation was considered the primary cause in the pathogenesis of MPD, the mutation status was not described in that report. We found JAK2 V617F mutation-positive essential thromobocythemia (ET) in a patient with KS. To the best of our knowledge, this case represents the first case report of JAK2 V617F mutation in a patient with KS. Furthermore, we also suggest the hypothesis that X chromosome aneuploidy as a "pre-JAK2" cytogenetic change may be associated with the development of clonal hematopoiesis and carcinogenesis, because of the finding of higher oncogenic potential of extra X chromosome. In this study, we present the first report of JAK2 V617F-positive ET in a patient with KS, as well as a review of the relevant literature.