My two sisters and I all have diagnosed Polycythemia Vera with the JAK2 mutation present. Neither parent have the mutation or the disease. From what I understan

My two sisters and I all have diagnosed Polycythemia Vera with the JAK2 mutation present. Neither parent have the mutation or the disease. From what I understand PV is not supposed to be hereditary and clusters like ours are very rare. In retrospect the earliest signs (at the time slightly elevated platelets) were present for me when I had a very bad bout of Epstein-Barr in my early 20s and was getting regular blood counts done for months, although the first diagnosis wasn't picked up until my eldest sister was in her early 40s and the disease was non-trivially advanced.