JAK2 (Janus kinase 2) is a gene that provides instructions for making a protein involved in the regulation of cell growth and division. JAK2 V617F mutation is a somatic point mutation that results in replacement of amino acid valine with the amino acid phenylalanine at position 617 in the protein. This mutation is found in a significant proportion of patients with myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). These are disorders characterized by the overproduction of blood cells in the bone marrow.

Determining the presence of the JAK2 V617F mutation is crucial for confirming the diagnosis, guiding treatment decisions, and assessing the prognosis for patients with MPNs. The presence of JAK2 V617F mutation helps confirm the diagnosis of MPNs, especially in cases of PV, ET, and PMF. The presence of this mutation in PV patients is associated with a higher risk of thrombosis. However, it is not specific to any one disease and can occur in multiple MPNs. JAK2 inhibitors, such as ruxolitinib, have been developed to specifically target the abnormal JAK2 pathway in patients with MPNs carrying the V617F mutation, offering a targeted treatment approach.