Molecularly Confirmed Polycythemia Vera with Elevated Endogenous Serum Erythropoietin Level: Diagnostic Algorithms Revisited.
Authors: Thurmes Paul J. , Steensma David P. 
Published: April 2020

Abstract
Background: It is widely accepted that an elevated serum endogenous erythropoietin (EPO) level in a patient presenting with erythrocytosis and a genuinely increased red cell mass makes a diagnosis of polycythemia vera (PV) extremely unlikely (Mossuz et al Haematologica2004:1194; Tefferi and Gilliland Mayo Clin Proc2005:947.) However, in the absence of a definitive molecular marker for PV, there is often uncertainty, especially when PV-associated clinical features are present. Here we describe 4 patients presenting with Budd-Chiari syndrome (BCS) and erythrocytosis who had EPO levels well above the normal reference range (Levy et al Hepatology1985:858), yet all had the newly described JAK2 V617F point mutation in myeloid cells, confirming PV.
Methods and Results: A 30-year-old man presented in March 2005 with ascites, mild splenomegaly, abnormal liver tests, and erythrocytosis (hemoglobin (Hb) 18.6 g/dL) with a normal platelet count (187 x 10(9)/L). BCS was diagnosed by Doppler ultrasonography, transjugular venogram, and liver biopsy. While bone marrow examination showed hypercellularity and megakaryocyte clustering consistent with chronic myeloproliferative disorder (CMPD), his EPO level was elevated to 32 U/L (normal 4–16 U/L), suggesting secondary erythrocytosis. Arterial oxygen saturation, Hb oxygen-dissociation curves (P50), molecular studies of the globin loci, Hb chromatography, and CT scans of the body were all normal. Granulocyte DNA demonstrated the JAK2 V617F mutation (heterozygous/mixed clonality), absent in buccal cells, confirming PV. Karyotype was normal and BCR/ABL was not present. The patient was treated with phlebotomy, warfarin, and hydroxyurea. One month later, his EPO level was markedly reduced at 13 U/L. We hypothesized that since hepatocytes express low levels of EPO, a remnant of fetal erythropoiesis, acute necrosis from BCS could lead to transient EPO surge even in the presence of chronic EPO suppression from PV. We then reviewed clinical data from all 33 patients at our institution since 1995 with BCS that was ultimately believed to be associated with PV. We identified 13 such patients in whom endogenous EPO levels were measured. Most had a low EPO level at the time of diagnosis (range of &lt;1.5 to 9 U/L), but 3 of these patients were found to have an elevated EPO level. DNA was extracted from archival samples from these 3 patients; JAK2 V617F mutation was detected in all 3. Clinical presentations were as follows:
Patient 1: 21-year-old woman with BCS and pulmonary embolus, Hb 15.9 mg/dL, EPO 28 U/L. Bone marrow biopsy was consistent with PV. Subsequent EPO level was 19U/L in the setting of progressive liver failure. Patient 2: 48-year-old woman with known PV receiving intermittent phlebotomy presented with BCS, Hb 17.2 mg/dL, EPO 25 U/L. Marrow was consistent with CMPD. Patient 3: 33-year-old woman presented with BCS, Hb 18.8 mg/dL, EPO 53 U/L. Bone marrow biopsy showed early CMPD.
Conclusion: Elevated EPO levels do not exclude the diagnosis of PV, especially in the presence of BCS with hepatic necrosis. These cases highlight the continuing challenges in accurate PV and CMPD diagnosis and emphasize the importance of complementing clinical assessment with molecular genetic testing, including JAK2 mutation analysis.