Post-Essential Thrombocythemia Myelofibrosis and Multiple Isodicentric Y Chromosomes: A Unique Case among a Rare Association.

Multiple isodicentric Y chromosomes [idic(Y)] is a rare cytogenetic abnormality, most exclusively described in constitutional karyotypes. Only recently has this entity been reported in hematologic neoplasms such as myeloid disorders, albeit these cases remain very scarce. The possible involvement of increasing copies of potential proto-oncogenes located on the multiple idic(Y) led to consider one of them, CRLF2, as a target for kinase inhibitors. We report here, to our knowledge, the first case of multiple idic(Y) in a patient with myelofibrosis secondary to essential thrombocythemia. The patient received ruxolitinib therapy with initial good clinical response.