A somatic point mutation (V617F) in exon 14 of the JAK2 gene is the most common mutation (found in more than 90% of the patients affected by PV) leading to the constitutive activation of the downstream signaling pathways, including the signal transducer and activator of transcription 5 (STAT5), extracellular signal-regulated kinase (ERK), and phosphatidylinositol 3-kinase/AKT [1]. Here, JAK2 is linked to acquired polycythemia vera.