Increase of CD34 positive cells in polycythaemia vera

The purpose of the present work was to evaluate the proliferative character of polycythaemia vera (PV). Therefore, in 15 patients with different stages of PV we assessed the level of CD34 positive (CD34+) cells in peripheral blood and bone marrow, erythroid colony growth of bone marrow cells and plasma erythropoietin (EPO). The mean concentration of CD34+ cells in blood was significantly increased in PV patients (9.0 +/- 11.2 x 10(3)/mL) compared to healthy controls (2.0 +/- 1.7 x 10(3)/mL). In aspirated bone marrow no such difference between PV and control subjects was present. Six patients with splenomegaly and/or requirement for chemotherapy had significantly higher mean blood levels of CD34+ cells compared to the remaining PV patients. All PV patients presented EPO independent erythroid colonies. Three PV patients with anaemia and long disease duration had high EPO levels.