Test ID: BPGMM    
2,3-Bisphosphoglycerate Mutase, Full Gene Sequencing Analysis, Varies

Diagnosis of 2,3-bisphosphoglycerate mutase deficiency in individuals with lifelong, unexplained erythrocytosis

Identifying genetic variant carriers in family members of an affected individual for the purposes of preconception genetic counseling

This test is not intended for prenatal diagnosis.

The BPGM gene encodes the enzyme 2,3-bisphosphoglycerate mutase (BPGM) that catalyzes the conversion of 1,3-bisphosphoglycerate to 2,3-bisphosphoglycerate (2,3-BPG), also known as 2,3-diphosphoglycerate (2,3-DPG), through the Luebering-Rapoport pathway. 2,3-BPG is a small molecule generated from glycolysis and is present in large amounts in red blood cells. It functions to stabilize the hemoglobin molecule and facilitates oxygen unloading at tissue sites. Therefore, 2,3-BPG concentrations affect the oxygen affinity of hemoglobin. Variations in this gene that result in a deficiency of 2,3-BPG can cause hereditary erythrocytosis.

This test can detect variants in BPGM that are associated with unexplained lifelong erythrocytosis due to bisphosphoglycerate mutase deficiency.

This evaluation is recommended for patients presenting with lifelong elevation in hemoglobin or hematocrit, usually with a positive family history of similar symptoms. Reported cases of 2,3- bisphosphoglycerate (BPG) deficiency have been associated with decreased p50 values (left-shifted oxygen-dissociation curve). Due to the rarity of this disorder, other more common causes of erythrocytosis should be excluded prior to ordering; see Erythrocytosis Evaluation Testing Algorithm in Special Instructions.

Polycythemia vera and chronic myeloproliferative neoplasm should be excluded prior to testing as they are more common causes of elevated hemoglobin values. A JAK2 V617F or JAK2 exon 12 variant should not be present. Patient serum erythropoietin levels are typically normal or elevated and oxygen dissociation p50 values decreased in test candidates. For a reflexive evaluation including p50 testing, hemoglobin electrophoresis, and variant analysis of genes associated with hereditary erythrocytosis, order REVE1 / Erythrocytosis Evaluation, Whole Blood.

Erythrocytosis (ie, increased red blood cell mass and elevated hemoglobin and hematocrit) may be primary, due to an intrinsic defect of bone marrow stem cells as in 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, 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 mechanism may be suspected.

Unlike PV, hereditary erythrocytosis is not associated with the risk of clonal evolution and most commonly presents as isolated erythrocytosis that has been present since childhood. Hereditary erythrocytosis may be caused by alterations in one of several genes and inherited in either an autosomal dominant or autosomal recessive manner.

Genetic variants causing hereditary erythrocytosis have been found in genes coding for alpha and beta hemoglobins, hemoglobin stabilization proteins (eg, 2,3-bisphosphoglycerate mutase: BPGM), the erythropoietin receptor (EPOR), and oxygen-sensing pathway enzymes (hypoxia-inducible factor: HIF, prolyl hydroxylase domain: PHD, and von Hippel Lindau: VHL), see table. High-oxygen-affinity hemoglobin variants and BPGM abnormalities result in a decreased p50 result, whereas those affecting EPOR, HIF, PHD, and VHL have normal p50 results. The true prevalence of variants causing hereditary erythrocytosis is unknown; however, very few cases of 2,3-BPG deficiency-associated hereditary erythrocytosis have been identified and this disorder is thought to be rare.

Erythrocytosis Testing

An interpretive report will be provided.

An interpretive report will be provided and will include specimen information, assay information, and whether the specimen was positive for any variations in the gene. If positive, the alteration will be correlated with clinical significance, if known.

This test does not detect large deletions and duplications in BPGM.

Polycythemia vera and acquired causes of erythrocytosis should be excluded before ordering this test. The p50 value should be decreased.

Certain genetic 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. Petousi N, Copley RR, Lappin TR, et al: Erythrocytosis associated with a novel missense mutation in the BPGM gene. Haematologica. 2014 Oct;99:e201-e204

2. Hoyer JD, Allen SL, Beutler E, et al: Erythrocytosis due to bisphosphoglycerate mutase deficiency with concurrent glucose-6-phosphate dehydrogenase (G-6-PD) deficiency. Am J Hematol. 2004;75(4):205-208

3. Rosa R, Prehu MO, Beuzard Y, Rosa J: The first case of a complete deficiency of diphosphoglycerate mutase in human erythrocytes. J Clin Invest. 1978;62(5):907-915

• Informed Consent for Genetic Testing
• Erythrocytosis Patient Information
• Erythrocytosis Evaluation Testing Algorithm
• Informed Consent for Genetic Testing (Spanish)