Masked polycythemia Vera (mPV): Results of an international study

We examined the baseline features and clinical outcomes of 140 patients presenting with JAK2V617F positivity and a bone marrow morphology conforming with WHO criteria of polycythemia vera (PV), but a hemoglobin level of 65 years and leukocyte count >10 × 10(9) /L. Our data suggest that mPV is a heterogeneous myeloproliferative neoplasia and not necessarily an early/ pre-polycythemic form of classical PV that at onset in a small fraction of patients clinically may mimic essential thrombocythemia. On the other hand, the majority mPV may have a longer prodrome of undiagnosed PV or a disease biology akin to primary myelofibrosis-post PV myelofibrosis that could explain the worsening of outcome in comparison to overt/classical manifestations.