More than 100 cases harboring both myeloproliferative neoplasms (MPN) and chronic lymphocytic leukaemia (CLL) have been reported, suggesting that the two diseases can coexist in one patient. However, the mechanism by which this phenomenon is caused remains unclear. In this study, one patient with polycythemia vera (PV) and CLL is examined. Identifications of the JAK2V617F and P53H179L/ P53R209fs mutations were obtained via targeted next generation sequencing. Furthermore, B lymphocytes and neutrophils were separated from peripheral blood. This led to the discovery that JAK2V617F occurs in neutrophil's compartment, with P53 mutations emerging in B lymphocytes. These results indicate that PV and CLL are independent clonal diseases in this case, rather than phenotypes derived from one clone.