Clinical features of acquired erythrocytosis: Low levels of serum erythropoietin in a subset of non-neoplastic erythrocytosis patients

Background Acquired erythrocytosis can be classified into polycythemia vera (PV) and non-neoplastic erythrocytosis (NNE). The vast majority of PV patients harbor JAK2 mutations, but differentiating JAK2 mutation-negative PV from NNE is challenging due to a lack of definitive molecular markers. Methods We studied the clinical features of 121 patients with erythrocytosis of which 47 (38.8%) were JAK2 mutation-positive and also fulfilled the diagnostic criteria for PV, and 67 (55.4%) JAK2 mutation-negative erythrocytosis patients who were diagnosed as NNE. Diagnosis was strictly based on driver mutation analysis and central pathology review. Results No JAK2 mutation-negative PV patients were found in our cohort. The NNE group showed significantly younger (p < 0.01) age with higher frequency of smoking (p < 0.001), alcohol consumption (p < 0.001), and diabetes mellitus (p < 0.05), whereas the PV group (n = 47) showed significantly higher white blood cell count, platelet count, and lactate dehydrogenase (p < 0.001). Although serum erythropoietin (EPO) levels were significantly higher in NNE compared to PV (p < 0.001), approximately 40% of the NNE patients had EPO levels below the lower range of normal, fulfilling a minor diagnostic criterion of PV and raising the possibility of PV misdiagnosis. Conclusion Low EPO levels in JAK2 mutation-negative erythrocytosis may not be a reliable diagnostic criterion for distinguishing PV from NNE.