Emergence of therapy-unrelated CML on a background of BCR-ABL-negative JAK2V617F-positive chronic idiopathic myelofibrosis.

We report the emergence of a chronic myeloid leukaemia (CML) during the course of a JAK2V617F-positive chronic idiopathic myelofibrosis (CIMF) in the absence of any myelosuppressive treatment. Although a response to imatinib was observed, the underlying myelofibrosis persisted after treatment and hydroxyurea was finally added to control the persistent thrombocytosis. Such rare patients with co-existing BCR-ABL translocation and JAK2V617F mutation must be identified in view of the possibility of targeted therapies. Moreover, the detection of BCR-ABL translocation appears to be crucial especially in the case of treated CIMF with an atypical course to identify CML before acute transformation.