Targeted NGS analysis reveals a complex genetic background of idiopathic erythrocytosis in a large Venetian family

Absolute erythrocytosis,due to an increased production of red blood cells,becomes manifest with hemoglobin(Hb)levels above 165 or 160 g/L or with a hematocrit(HCT)above 51％and 48％in males and females,respectively.1 A minority of patients have polycythemia vera(PV);acquired secondary erythrocytosis frequently occurs due to appro-priate or inappropriate erythropoietin(EPO)excess,while congenital secondary erythrocytosis may derive from ge-netic defects causing tissue hypoxia.