The differentiation between
primary myelofibrosis (PMF) and essential thrombocythaemia (ET) may be difficult especially in early-stage disease. In PMF, increased levels of inflammatory
cytokines induce impaired
iron utilisation and disturbed erythropoiesis. In conditions with impaired
iron support to erythropoiesis,
zinc protoporphyrin (ZPP) is produced instead of
heme. Here, we investigate whether ZPP concentration can be useful in the differentiation between PMF and ET. Seventy newly diagnosed patients (PMF, n=24; ET, n=46) were analysed. Intraerythrocytic ZPP concentration (normal≤40 μmol/mol
heme) was measured by an Aviv front-face haematofluorometer. In PMF, ZPP concentrations were significantly increased when compared to ET (99±37 μmol/mol
heme vs. 36±13 μmol/mol
heme, p<0.0001). There was also a significant difference between early-stage PMF and advanced disease (77±30 μmol/mol
heme vs. 122±31 μmol/mol
heme, p=0.003). ZPP>76 μmol/mol
heme as observed in 71% of PMF patients were not seen in ET. In PMF patients responding to immunosuppressive treatment (n=4), the increase in haemoglobin was accompanied by declining ZPP. In summary, by detecting the disturbed
iron metabolism common in PMF, ZPP may assist in the differentiation between PMF and ET. Concentrations>60 μmol/mol
heme are unlikely in ET if
iron deficiency is excluded. ZPP determination is also useful for monitoring the effect of
therapy in PMF.