Several studies have shown that treatment of polycythemia vera (PV) and essential thrombocythemia (ET) with interferon-alpha2 (IFN-alpha2) is associated with a decrease in the JAK2 V617F mutational load together with complete hematological responses and in a subset of patients even with normalisation of the bone marrow. We report a PV patient, who – after having achieved a major molecular remission with normalisation of the bone marrow and off IFN-alpha2b for about 5 years – had a rapid rise in the hematocrit value and the JAK2 V617F allele burden within months but still with a normal bone marrow and a slightly enlarged spleen. This report adds novel information on the dynamics of the JAK2 V617F allele burden from the very early PV-stage with normal peripheral blood counts and low burden JAK2 V617F to in the hematocrit value.