Since the possibility of the myeloproliferative disease could not be completely ruled out analysis of Janus kinase-2 (JAK-2) gene- (V617F mutation), JAK2 exon 12-, calreticulin (CALR)-, and myeloproliferative leukemia virus oncogene (MPL) mutations were done with negative results, erythropoietin level was decreased. The gene discussed is MPL; the disease is myeloproliferative disorder.