Long-term Effects of the Janus Kinase 1/2 Inhibitor Ruxolitinib on Pulmonary Hypertension and the Cardiac Function in a Patient with Myelofibrosis

Constitutive activation of the Janus kinase/signal transduction and activator of transcription (JAK-STAT) signaling pathway plays a central role in the pathogenesis of myelofibrosis (MF) and pulmonary hypertension (PH) is a known complication of MF. On the other hand, it has been proposed that the JAK-STAT pathway, especially signal transducer and activation of transcription (STAT) 3 activation, protects cardiomyocytes from various stresses. We describe the case of a patient with MF-associated PH who developed left ventricular dysfunction after five years of treatment with the JAK 1/2 inhibitor, ruxolitinib. This is the first report with histopathological findings that demonstrate possible contradictory effects of a JAK 1/2 inhibitor: improvement of MF-associated PH and cardiotoxicity.