In contrast to primary erythrocytosis where – in most cases – a myeloproliferative neoplasm (i.e., polycythemia vera [PV]) induces a overproduction of red blood cells, polyglobulia in secondary erythrocytosis is the result of either a hypoxic stimulus (i.e., tissue hypoxemia in chronic obstructive pulmonary disease and smoking), paraneoplastic erythropoietin overproduction (i.e., in renal cell carcinoma) or is medicament-induced as in TIE. Here, EPO is linked to acquired polycythemia vera.