JAK2(V617F) allele burden in polycythemia vera: burden of proof

Polycythemia vera (PV) is a hematopoietic stem cell neoplasm defined by activating somatic mutations in the JAK2 gene and characterized clinically by overproduction of red blood cells, platelets, and neutrophils; a significant burden of disease-specific symptoms; high rates of vascular events; and evolution to a myelofibrosis phase or acute leukemia. The JAK2(V617F) variant allele frequency (VAF) is a key determinant of outcomes in PV, including thrombosis and myelofibrotic progression. Here, we critically review the dynamic role of JAK2(V617F) mutation burden in the pathogenesis and natural history of PV, the suitability of JAK2(V617F) VAF as a diagnostic and prognostic biomarker, and the utility of JAK2(V617F) VAF reduction in PV treatment.