Hence, the term masked PV (mPV) is used for those with JAK2-mutated patients but with pre-polycythaemic disease manifestation and BM morphology concordant with PV plus raised HB levels between 16.0 and 18.5 g/dL for men and 16.5 g/dL for women. The gene discussed is JAK2; the disease is acquired polycythemia vera.