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M, Emre S, et al: Prospective longitudinal analysis of quantitative Epstein-Barr virus polymerase chain
reaction in pediatric liver transplant recipients. Transplantation 1999;67(7):1068-1070 5. Green M,
Cacciarelli TV, Mazariegos GV, et al: Serial measurement of Epstein-Barr viral load in peripheral blood
in lymphoproliferative disease. Transplantation 1998;66(12):1641-1644 6. Lau AH, Soltys K, Sindhi RK,
et al: Chronic high Epstein-Barr viral load carriage in pediatric small bowel transplant recipients. Pediatr
Transplant Jan 20
Erythrocytosis Evaluation
Clinical Information: Erythrocytosis (increased RBC mass or polycythemia) may be primary, due to
an intrinsic defect of bone marrow stem cells (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, renal 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 present. A less common cause of secondary
polycythemia is the presence of a high-oxygen-affinity hemoglobin. Hemoglobins with increased oxygen
(O2) affinity commonly result in erythrocytosis caused by an O2 unloading problem at the tissue level.
The most common symptoms are headache, dizziness, tinnitus, and memory loss. The affected individuals
are plethoric, but not cyanotic. Patients with a high-oxygen-affinity hemoglobin may present with an
increased erythrocyte count, hemoglobin concentration, and hematocrit, but normal leukocyte and platelet
counts. The p50 and 2,3-bisphosphoglycerate (2,3-BPG, also known as 2,3-DPG) values are low. Changes
to the amino acid sequence of the hemoglobin molecule may distort the molecular structure, affecting O2
transport and the binding of 2,3-BPG. 2,3-BPG is critical to O2 transport of erythrocytes because it
regulates the O2 affinity of hemoglobin. A decrease in the 2,3-BPG concentration within erythrocytes
results in greater O2 affinity of hemoglobin and reduction in O2 delivery to tissues. A few cases of
erythrocytosis have been described as being due to a reduction in 2,3-BPG formation. This is most
commonly due to mutations in the converting enzyme, bisphosphoglycerate mutase (BPGM). Mutations
in the genes EPOR, EPAS1(HIF2A), EGLN1(PHD2), and VHL also cause hereditary erythrocytosis and a
subset are associated with subsequent pheochromocytoma and paragangliomas. The prevalence of these
mutations is unknown, but they appear less prevalent than mutations that cause high-oxygen-affinity
hemoglobin variants, and much less prevalent than polycythemia vera. Because there are many causes of
erythrocytosis, an algorithmic and reflexive testing strategy is useful. Initial JAK2 V617F mutation
testing and serum Epo levels are important with p50 results further stratifying JAK2-negative cases.
Useful For: The definitive evaluation of an individual with JAK2-negative erythrocytosis associated
with lifelong sustained increased RBC mass, elevated RBC count, hemoglobin, or hematocrit
Interpretation: The evaluation includes testing for a hemoglobinopathy and oxygen (O2) affinity of
the hemoglobin molecule. An increase in O2 affinity is demonstrated by a shift to the left in the O2
dissociation curve (decreased p50 result). A hematopathologist expert in these disorders will evaluate the
case, appropriate tests are performed, and an interpretive report is issued.
Reference Values:
Definitive results and an interpretive report will be provided.
Clinical References: 1. Patnaik MM, Tefferi A: The complete evaluation of erythrocytosis:
congenital and acquired. Leukemia 2009 May;23(5):834-844 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 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;52:280-284 6. Lee F: Genetic causes of erythrocytosis and the
oxygen-sensing pathway. Blood Rev 2008;22:321-332 7. Merchant SH, Oliveira JL, Hoyer JD,
Viswanatha DS: Erythrocytosis. In Hematopathology. Second edition. Edited by ED His. Philadelphia,
Elsevier Saunders, 2012, pp 722-723 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
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