The myeloproliferative neoplasms (MPN) are clonal, hematopoietic stem cell-derived diseases characterised by bone marrow proliferation of one or more of the myeloid cell lineages with the main subtypes being polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The diagnosis and classification of these diseases is dependent on clinical, hematological, histo-morphological and molecular genetic findings. The most commonly acquired mutation associated with MPN is the JAK2 V617F, occurring in approximately 95% of PV cases and in 50–60% of ET and PMF patients.