Concurrence of multiple myeloma and idiopathic erythrocytosis.

The association of erythrocytosis and multiple myeloma is rare. We encountered a 76-year-old male patient with erythrocytosis followed by the diagnosis of multiple myeloma 8 months later. Related laboratory examinations revealed absolute erythrocytosis, normal oxygen saturation and erythropoietin (EPO) levels, the absence of endogenous erythroid colony (EEC) and JAK2-V617F mutations. The diagnosis of idiopathic erythrocytosis (IE), instead of polycythemic vera (PV), was made. In the literature, about 20 cases of erythrocytosis associated with myeloma can be found. Based on elevated EPO levels, 2 of such cases should be considered secondary erythrocytosis while others are reported as PV. None of them is considered to be have idiopathic erythrocytosis. Our present case is the first one with multiple myeloma developing in a patient with the diagnosis well established by extensive laboratory workup. The pathogenic role of these two entities remains to be established.