JAK2(V617F) allele burden in polycythemia vera correlates with grade of myelofibrosis, but is not substantially affected by therapy.

In a series of 105 patients with polycythemia vera, we retrospectively determined whether the JAK2(V617F) mutation correlated with severity of disease phenotype. Higher JAK2(V617F) allele burden correlated with more advanced myelofibrosis, greater splenomegaly, and higher white blood cell count, but not with age, gender, hematocrit level, or frequency of phlebotomy prior to cytoreductive therapy. Although a subgroup at increased risk for thrombosis was not clearly defined, there was a suggestion that frequency of thrombosis increased as the JAK2(V617F) allele burden increased. The JAK2(V617F) allele burden did not change significantly in treated patients with serial JAK2 analyses.