Assessing EPOR in the evaluation of an individual with JAK2-negative erythrocytosis associated with lifelong sustained increased red blood cell (RBC) mass, elevated RBC count, hemoglobin, or hematocrit
This test is a third-order test and should be ordered when the patient meets the following criteria: diagnosis of lifelong and sustained erythrocytosis, JAK2 V617F is negative and serum erythropoietin levels are decreased to normal.
Only orderable as part of a profile. For more information see HEMP / Hereditary Erythrocytosis Mutations, Whole Blood.
Polymerase Chain Reaction (PCR)/Sanger Sequencing
EPOR
Erythrocytosis
Polycythemia
Whole blood
Only orderable as part of a profile. For more information see HEMP / Hereditary Erythrocytosis Mutations, Whole Blood.
Container/Tube: Lavender top (EDTA)
Specimen Volume: 3 mL
Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.
0.5 mL
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
| Moderately to severely clotted | Reject |
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole blood | Refrigerated (preferred) | 30 days | |
| Ambient | 14 days |
Assessing EPOR in the evaluation of an individual with JAK2-negative erythrocytosis associated with lifelong sustained increased red blood cell (RBC) mass, elevated RBC count, hemoglobin, or hematocrit
This test is a third-order test and should be ordered when the patient meets the following criteria: diagnosis of lifelong and sustained erythrocytosis, JAK2 V617F is negative and serum erythropoietin levels are decreased to normal.
Erythrocytosis (ie, increased red blood cell [RBC] mass or polycythemia) may be primary, due to an intrinsic defect of bone marrow stem cells (ie, polycythemia vera: PV), or secondary, in response to increased serum erythropoietin (EPO) levels. Secondary erythrocytosis is associated with a number of disorders including chronic lung disease, chronic increase in carbon monoxide (due to smoking), cyanotic heart disease, high-altitude living, kidney cysts and tumors, hepatoma, and other EPO-secreting tumors. When these common causes of secondary erythrocytosis are excluded, a heritable cause involving hemoglobin or erythrocyte regulatory mechanisms may be suspected.
Unlike polycythemia vera, hereditary erythrocytosis is not associated with the risk of clonal evolution and should present with isolated erythrocytosis that has been present since birth. A small subset of cases are associated with pheochromocytoma or paraganglioma formation. Hereditary erythrocytosis is caused by variants in several genes and may be inherited in either an autosomal dominant or autosomal recessive manner. A family history of erythrocytosis would be expected in these cases, although it is possible for new alterations to arise in an individual.
The genes coding for hemoglobin, beta globin and alpha globin (high-oxygen-affinity hemoglobin variants), hemoglobin-stabilization proteins (2,3 bisphosphoglycerate mutase: BPGM), and the erythropoietin receptor, EPOR, and oxygen-sensing pathway enzymes (hypoxia-inducible factor: HIF/EPAS1, prolyl hydroxylase domain: PHD2/EGLN1, and von Hippel Lindau: VHL) can result in hereditary erythrocytosis (see Table). The true prevalence of hereditary erythrocytosis-causing alterations is unknown. The hemoglobin genes, HBA1/HBA2 and HBB are not assayed in this profile.
Table. Genes Associated with Hereditary Erythrocytosis
| Gene | Inheritance | Serum EPO |
| JAK2 V617F | Acquired | Decreased |
| JAK2 exon 12 | Acquired | Decreased |
| EPOR | Dominant | Decreased |
| PHD2/EGLN1 | Dominant | Normal level |
| BPGM | Recessive | Normal level |
| Beta Globin | Dominant | Normal level to increased |
| Alpha Globin | Dominant | Normal level to increased |
| HIF2A/EPAS1 | Dominant | Normal level to increased |
| VHL | Recessive | Normal level to increased |
The oxygen-sensing pathway functions through an enzyme, hypoxia-inducible factor (HIF), which regulates RBC mass. A heterodimer protein comprised of alpha and beta subunits, HIF functions as a marker of depleted oxygen concentration. When present, oxygen becomes a substrate mediating HIF-alpha subunit degradation. In the absence of oxygen, degradation does not take place and the alpha protein component is available to dimerize with a HIF-beta subunit. The heterodimer then induces transcription of many hypoxia response genes including EPO, VEGF, and GLUT1. HIF-alpha is regulated by von Hippel-Lindau (VHL) protein-mediated ubiquitination and proteosomal degradation, which requires prolyl hydroxylation of HIF proline residues. The HIF-alpha subunit is encoded by the HIF2A (EPAS1) gene. Enzymes important in the hydroxylation of HIF-alpha are the prolyl hydroxylase domain proteins, of which the most significant isoform is PHD2, which is encoded by the PHD2 (EGLN1) gene. Genetic variants resulting in altered HIF-alpha, PHD2, and VHL proteins can lead to clinical erythrocytosis. A small subset of variants in PHD2/EGLN1 and HIF2A/EPAS1 have also been detected in erythrocytic patients presenting with paragangliomas or pheochromocytomas.
Truncating variants in the EPOR gene coding for the erythropoietin receptor can result in erythrocytosis through loss of the negative regulatory cytoplasmic SHP-1 binding domain leading to EPO hypersensitivity. All currently known alterations have been localized to exon 8 and are heterozygous truncating variants. EPOR variants are associated with decreased EPO levels (see Table).
Only orderable as part of a profile. For more information see HEMP / Hereditary Erythrocytosis Mutations, Whole Blood.
An interpretive report will be provided.
Assessing EPOR in the evaluation of an individual with JAK2-negative erythrocytosis associated with lifelong sustained increased red blood cell (RBC) mass, elevated RBC count, hemoglobin, or hematocrit
Polycythemia vera and acquired causes of erythrocytosis should be excluded before ordering this evaluation.
This test will not detect somatic or gonadal mosaicism.
Certain sequence alterations have no clinical manifestations and, in essence, are clinically benign. Correlation with all relevant clinical information is necessary to provide appropriate patient care.
1. Patnaik MM, Tefferi A: The complete evaluation of erythrocytosis: congenital and acquired. Leukemia. 2009 May;23(5):834-844. doi: 10.1038/leu.2009.54
2. McMullin MF: The classification and diagnosis of erythrocytosis. Int J Lab Hematol. 2008;30:447-459
3. Percy MJ, Lee FS: Familial erythrocytosis: molecular links to red blood cell control. Haematologica. 2008 Jul;93(7):963-967. doi: 10.3324/haematol.13250
4. Huang LJ, Shen YM, Bulut GB: Advances in understanding the pathogenesis of primary familial and congenital polycythaemia. Br J Haematol. 2010 Mar;148(6):844-852
5. Maran J, Prchal J: Polycythemia and oxygen sensing. Pathologie Biologie. 2004 Jun;52(5):280-284
6. Lee F: Genetic causes of erythrocytosis and the oxygen-sensing pathway. Blood Rev. 2008 Nov;22(6):321-332
7. Merchant SH, Oliveira JL, Hoyer JD, Viswanatha DS: Erythrocytosis. In: His ED, ed. Hematopathology. 2nd ed. Elsevier Saunders; 2012:22-723
8. Zhuang Z, Yang C, Lorenzo F, et al: Somatic HIF2A gain-of-function mutations in paraganglioma with polycythemia. N Engl J Med. 2012 Sep 6;367(10):922-930
9. Ladroue C, Carcenac R, Leporrier M, et al: PHD2 mutation and congenital erythrocytosis with paraganglioma. N Engl J Med. 2008 Dec 18;359(25):2685-2692
10. Lorenzo FR, Yang C, Ng Tang Fui M, et al: A novel EPAS1/HIF2A germline mutation in congenital polycythemia with paraganglioma. J Mol Med. 2013 Apr;91(4):507-512
11. Tarade D, Robinson CM, Lee JE, Ohh M: HIF-2alpha-pVHL complex reveals broad genotype-phenotype correlations in HIF-2aalpha-driven disease. Nat Commun. 2018 Aug 22;9(1):3359
12. Oliveira JL: Algorithmic evaluation of hereditary erythrocytosis: Pathways and caveats. Int J Lab Hematol. 2019 May;41 Suppl 1:89-94. doi: 10.1111/ijlh.13019
DNA is extracted from whole blood and amplified in 7 separate polymerase chain reaction (PCR) reactions to cover EPOR exon 8, HIF2A exons 9 and 12, and PHD2 exons 1 through 5. PCR products are then sequenced by the Sanger sequencing method and analyzed with sequencing software. Patient sequence results are compared with the genomic reference sequences and the single nucleotide variants known to occur in the genes. If a variant is detected, the messenger RNA reference sequence will be used to determine the amino acid number and resulting amino acid change, if there is one.(Percy MJ, McMullin MF, Roques AW, et al: Erythrocytosis due to a mutation in the erythropoietin receptor gene. Br J Haematol. 1998 Feb;100(2):407-410; Martini M, Teofili L, Cenci T, et al: A novel heterozygous HIF2a[M535I] mutation reinforces the role of oxygen sensing pathway disturbances in the pathogenesis of familial erythrocytosis. Haematologica. 2008;93[7]:1068-1071; Percy MJ, Zhao Q, Flores A, et al: A family with erythrocytosis establishes a role for prolyl hydroxylase domain protein 2 in oxygen homeostasis. PNAS. 2006;103[3]:654-659; Oliveira JL, Coon LM, Frederick LA, et al: Genotype-phenotype correlation of hereditary erythrocytosis mutations, a single center experience. Am J Hematol. 2018 May 23. doi: 10.1002/ajh.25150)
Monday through Friday
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.
81479
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| EPOR | EPOR Gene, Mutation Analysis, B | In Process |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| 34645 | EPOR Gene Sequencing Result | 82939-0 |