Erythrocytosis: Diagnosis and investigation.

An absolute erythrocytosis is present when the red cell mass is greater than 125% of the predicted. This is suspected when the hemoglobin or hematocrit is above the normal range. An erythrocytosis can be classified as primary or secondary and congenital or acquired. The commonest primary acquired disorder is polycythemia vera. The diagnostic criteria for PV have evolved over time and this is the main diagnosis managed in hematology clinics. There are a variety of rare congenital causes both primary and secondary. In particular in young patients and/or those with a family history a congenital cause is suspected. There remains a larger cohort with acquired erythrocytosis mainly with non-hematological pathology. In order to explore for a cause of erythrocytosis, measurement of the erythropoietin level is a first step. A low erythropoietin level indicates a primary cause and a normal or elevated level indicates a secondary etiology. Further investigation is then dictated by initial findings and includes mutational testing with PCR and NGS for those in whom a congenital cause is suspected. Following this possibly bone marrow biopsy, scans, and further investigation as indicated by history and initial findings. Investigation is directed toward the identification of those with a hematological disorder which would be best managed following guidelines in hematology clinics and referral elsewhere in those for whom there are non-hematological reasons for the elevated hemoglobin.

Heterozygosity for bisphosphoglycerate mutase deficiency expressing clinically as congenital erythrocytosis: A case series and literature review.

Erythrocytosis is associated with increased red blood cell mass and can be either congenital or acquired. Congenital secondary causes are rare and include germline variants increasing haemoglobin (Hb)-oxygen affinity (e.g., Hb or bisphosphoglycerate mutase (BPGM) variants) or affecting oxygen-sensing pathway proteins. Here, we describe five adults from three kindreds with erythrocytosis associated with heterozygosity for BPGM variants, including one novel. Functional analyses showed partial BPGM deficiency, reduced 2,3-bisphosphoglycerate levels and/or increased Hb-oxygen affinity. We also review currently known BPGM variants. This study contributes to raising awareness of BPGM variants, and in particular that heterozygosity for BPGM deficiency may already manifest clinically.

Identification of Two Novel EPOR Gene Variants in Primary Familial Polycythemia: Case Report and Literature Review.

Primary familial and congenital polycythemia is a rare disease characterized by an increase in red cell mass that may be due to pathogenic variants in the EPO receptor (EPOR) gene. To date, 33 genetic variants have been reported to be associated. We analyzed the presence of EPOR variants in two patients with polycythemia in whom JAK2 pathogenic variants had been previously discarded. Molecular analysis of the EPOR gene was performed by Sanger sequencing of the coding regions and exon/intron boundaries of exon 8. We performed in vitro culture of erythroid progenitor cells. Segregation studies were done whenever possible. The two patients studied showed hypersensitivity to EPO in in vitro cultures. Analysis of the EPOR gene unveiled two novel pathogenic variants. Genetic testing of asymptomatic relatives could guarantee surveillance and proper management.

Effects of idiopathic erythrocytosis on the left ventricular diastolic functions and the spectrum of genetic mutations: A case control study.

BACKGROUND: We have aimed at exposing left ventricular diastolic functions and the presence of known genetic mutations for familial erythrocytosis, in patients who exhibit idiopathic erythrocytosis. METHODS: Sixty-four patients with idiopathic erythrocytosis (mean age, 46.4 ± 2.7 years) and 30 age-matched healthy subjects were prospectively evaluated. The regions of interest of the erythropoietin receptor, hemoglobin beta-globin, von Hippel-Lindau, hypoxia-inducible factor 2 alpha, and Egl-9 family hypoxia-inducible factor genes were amplified by PCR. Left ventricular (LV) mass was measured by M-mode and 2-dimensional echocardiography. LV diastolic functions were assessed by conventional echocardiography and tissue Doppler imaging. RESULTS: As a result of genetic analyses, genetic mutations for familial erythrocytosis were detected in 5 patients. It has been observed in our study that the risk of cardiovascular disorders is higher in patients. Interventricular septum thickness, left atrial diameter, and some diastolic function parameters such as deceleration time and isovolumetric relaxation time have been found to be significantly higher in idiopathic erythrocytosis group than in the controls. CONCLUSION: This study has shown that LV diastolic functions were impaired in patients with idiopathic erythrocytosis. In this patient group with increased risk of cardiovascular disorders, the frequent genetic mutations have been detected in 5 patients only. Therefore, further clinical investigations are needed as novel genetic mutations may be discovered in patients with idiopathic erythrocytosis because of cardiovascular risk.

Novel mutations in EPO-R and oxygen-dependent degradation (ODD) domain of EPAS1 genes-a causative reason for Congenital Erythrocytosis.

Congenital Erythrocytosis (CE) can be primary or secondary due to the mutations in genes involved in the erythropoietin receptor and oxygen sensing pathway. In this study, 42 patients with 38 unrelated patients and one family (4 patients) who were JAK-2 mutation (both exon 12 and exon 14) negative with high haematocrit values were investigated. The Endogenous Erythroid colony (EEC) assay was performed in all patients, interestingly EEC colonies were high in EPAS1 and EPOR mutated patients compared to non-mutated patients. The sequence analysis of EPAS1 (exon 12), EPO-R (exon-8), VHL (exon-3), and EGLN1 (exon-1) genes in all these patients showed 19% of patients (8/42) had mutations, in exon12 of EPAS1 and exon 8 of EPO-R genes. Two novel missense mutations MW_600850:c.1183G>C, MW_600851:c.1028A>C in EPO-R gene were observed in the study group. One new MW_600849:c.1969C>T nonsense mutation and five MW_619914:c.1715A>G, MW_619915:c.1694G>T, MW_619916:c.1634T>C, MW_600852:c.1771C>G, MW_600848:c.1859G>A novel missense mutations were observed in the EPAS1 gene. Among them, 4 mutations p. (Gln572Arg), p. (Ser565Ile), p. (Ile545Thr), p. (Gln591Glu) in the ODD (Oxygen-dependent degradation) domain of HIF2α, all these variations contributed to the formation of non-functional HIF2α. No mutations were observed in VHL and EGLN1 genes. Using in silico analysis we observed that these mutations contributed to major conformational changes in the HIF2α protein making it non-functional. The mutations in the EPAS1 gene were heterozygous and show autosomal dominant inheritance patterns and we observed in one family. These novel mutations in the EPAS1 (75% (6/8)) and 25% (2/8) EPO-R genes correlating with EEC positivity were observed for the first time in India in CE patients.

NGS Evaluation of a Bernese Cohort of Unexplained Erythrocytosis Patients.

(1) Background: Clinical and molecular data on patients with unexplained erythrocyto-sis is sparse. We aimed to analyze the clinical and molecular features of patients with congenital erythrocytosis in our tertiary reference center. (2) Methods: In 34 patients with unexplained erythrocytosis, a 13-gene Next-Generation Sequencing erythrocytosis panel developed at our center was conducted. (3) Results: In 6/34 (18%) patients, eight different heterozygous gene variants were found. These patients were, therefore, diagnosed with congenital erythrocytosis. Two patients had two different gene variants each. All variants were characterized as variants of unknown significance as they had not previously been described in the literature. The rest of the patients (28/34, 82%) had no detected gene variants. (4) Conclusions: Our experience shows that the NGS panel can be helpful in determining the reasons for persistent, unexplained erythrocytosis. In our cohort of patients with erythrocytosis, we identified some, thus far unknown, gene variants which may explain the clinical picture. However, further investigations are needed to determine the relationship between the molecular findings and the phenotype.

Heritable disorders of oxygen sensing.

Hypoxia-inducible factors (HIFs) activate gene transcription in response to reduced O2 availability and play critical roles in development, physiology, and disease pathogenesis. Mutations that dysregulate HIF activity are the genetic basis for tumor predisposition in the von Hippel-Lindau syndrome and excess red blood cell production in hereditary erythrocytosis.

Congenital erythrocytosis - A condition behind recurrent thromboses: A case report and literature review.

Congenital erythrocytosis (CE) is an extremely rare disease and an infrequent cause of heamoglobin and haematocrit elevation. Genetic testing of CE is not widely available. Patients in whom a cause of erythrocytosis is not identified are classified as idiopathic erythrocytosis (IE) patients. In some types of CE thrombotic events have been reported but there is little hard evidence to advise on management in asymptomatic patients. Similarly is true for patients with IE. We describe a young patient who suffered several thromboembolic complications before the diagnosis of CE type 4 was established.

Familial erythrocytosis 2 and von Hippel-Lindau disease in the same pediatric patient.

BACKGROUND: Patients with familial erythrocytosis type 2 have no increased risk of von Hippel-Lindau-associated tumors, although mutations in the VHL gene cause both pathologies. CASE REPORT: We present a case of a compound heterozygote patient with von Hippel-Lindau disease and familial erythrocytosis type 2. One of the mutations found in our patient, c.416C>G (p.Ser139Cys) of the VHL gene, has not been previously reported. This case is the second one reported where von Hippel-Lindau disease and familial erythrocytosis type 2 coexist in the same individual. CONCLUSIONS: Despite the low frequency of familial erythrocytosis type 2 in patients with von Hippel-Lindau disease, the possibility of this diagnosis should be considered to avoid unnecessary invasive studies to explain the polyglobulia in these patients and guarantee an adequate follow-up and vigilance of both diseases.

Heritable disorders of oxygen sensing.

Hypoxia-inducible factors (HIFs) activate gene transcription in response to reduced O2 availability and play critical roles in development, physiology, and disease pathogenesis. Mutations that dysregulate HIF activity are the genetic basis for tumor predisposition in the von Hippel-Lindau syndrome and excess red blood cell production in hereditary erythrocytosis.

Diagnosis and management of non-clonal erythrocytosis remains challenging: a single centre clinical experience.

Erythrocytosis has a diverse background. While polycythaemia vera has well defined criteria, the diagnostic approach and management of other types of erythrocytosis are more challenging. The aim of study was to retrospectively analyse the aetiology and management of non-clonal erythrocytosis patients referred to a haematology outpatient clinic in an 8-year period using a 3-step algorithm. The first step was inclusion of patients with Hb > 185 g/L and/or Hct > 0.52 in men and Hb > 165 g/L and/or Hct > 0.48 in women on two visits ≥ two months apart, thus confirming true erythrocytosis. Secondly, polycythaemia vera was excluded and secondary causes of erythrocytosis (SE) identified. Thirdly, idiopathic erythrocytosis patients (IE) were referred to next-generation sequencing for possible genetic background evaluation. Of the 116 patients, 75 (65%) are men and 41 (35%) women, with non-clonal erythrocytosis 34/116 (29%) had SE, 15/116 (13%) IE and 67/116 (58%) stayed incompletely characterized (ICE). Patients with SE were significantly older and had significantly higher Hb and Hct compared to patients with IE. Most frequently, SE was attributed to obstructive sleep apnoea and smoking. Phlebotomies were performed in 56, 53 and 40% of patients in the SE, IE, and ICE group, respectively. Approx. 70% of patients in each group received aspirin. Thrombotic events were registered in 12, 20 and 15% of SE, IE and ICE patients, respectively. Congenital erythrocytosis type 4 (ECYT4) was diagnosed in one patient. The study demonstrates real-life management of non-clonal erythrocytosis which could be optimized using a 3-step diagnostic algorithm.

Congenital erythrocytosis.

Erythrocytosis, or increased red cell mass, may be labeled as primary or secondary, depending on whether the molecular defect is intrinsic to the red blood cells/their precursors or extrinsic to them, the latter being typically associated with elevated erythropoietin (EPO) levels. Inherited/congenital erythrocytosis (CE) of both primary and secondary types is increasingly recognized as the cause in many patients in whom acquired, especially neoplastic causes have been excluded. During the past two decades, the underlying molecular mechanisms of CE are increasingly getting unraveled. Gain-in-function mutations in the erythropoietin receptor gene were among the first to be characterized in a disorder termed primary familial and congenital polycythemia. Another set of mutations affect the components of the oxygen-sensing pathway. Under normoxic conditions, the hypoxia-inducible factor (HIF), upon hydroxylation by the prolyl-4-hydroxylase domain protein 2 (PHD2) enzyme, is degraded by the von Hippel-Lindau protein. In hypoxic conditions, failure of prolyl hydroxylation leads to stabilization of HIF and activation of the EPO gene. CE has been found to be caused by loss-of-function mutations in VHL and PHD2/EGLN1 as well as gain-of-function mutations in HIF-2α (EPAS1), all resulting in constitutive activation of EPO signaling. Apart from these, globin gene mutations leading to formation of high oxygen affinity hemoglobins also cause CE. Rarely, bisphosphoglycerate mutate mutations, affecting the 2,3-bisphosphoglycerate levels, can increase the oxygen affinity of hemoglobin and cause CE. This narrative review examines the current mutational spectrum of CE and the distinctive pathogenetic mechanisms that give rise to this increasingly recognized condition in various parts of the world.

Genetic analysis of 39 erythrocytosis and hereditary hemochromatosis-associated genes in the Slovenian family with idiopathic erythrocytosis.

BACKGROUND: Erythrocytosis is a condition with an excessive number of erythrocytes, accompanied by an elevated haemoglobin and/or haematocrit value. Congenital erythrocytosis has a diverse genetic background with several genes involved in erythropoiesis. In clinical practice, nine genes are usually examined, but in approximately 70% of patients, no causative mutation can be identified. In this study, we screened 39 genes, aiming to identify potential disease-driving variants in the family with erythrocytosis of unknown cause. PATIENTS AND METHODS: Two affected family members with elevated haemoglobin and/or haematocrit and negative for acquired causes and one healthy relative from the same family were selected for molecular-genetic analysis of 24 erythrocytosis and 15 hereditary haemochromatosis-associated genes with targeted NGS. The identified variants were further analysed for pathogenicity using various bioinformatic tools and review of the literature. RESULTS: Of the 12 identified variants, two heterozygous variants, the missense variant c.471G>C (NM_022051.2) (p.(Gln157His)) in the EGLN1 gene and the intron variant c.2572-13A>G (NM_004972.3) in the JAK2 gene, were classified as low-frequency variants in European population. None of the two variants were present in a healthy family member. Variant c.2572-13A>G has potential impact on splicing by one prediction tool. CONCLUSION: For the first time, we included 39 genes in the erythrocytosis clinical panel and identified two potential disease-driving variants in the Slovene family studied. Based on the reported functional in vitro studies combined with our bioinformatics analysis, we suggest further functional analysis of variant in the JAK2 gene and evaluation of a cumulative effect of both variants.

Novel mutations in the EPO-R, VHL and EPAS1 genes in the Congenital Erythrocytosis patients.

Congenital erythrocytosis (CE) can be classified as primary and secondary and 82 consecutive patients of erythrocytosis who were JAK-2 mutation negative, were further investigated. The genomic DNA was extracted from all the patients and the EPO-R, VHL, EGLN1 and EPAS1 genes were PCR amplified and sequenced. The sequence analysis showed (28/82) 34.14% patients had mutations. Among them, (19/28) 67.86% patients had mutations in exon 8 of EPO-R gene, of which six were novel missense mutations, p.(Gly418Ala), p.(Gly390Ala), p.(Ala411Thr), p.(Gly475Val), p.(Glu490Asp), p.(Glu362Gln) and three were novel frameshift mutations, p.(Glu336*), p.(Pro327Hisfs*68), p.(Gly479Alafs*37). All these EPO-R patients were heterozygotes and were forming endogenous erythrocyte colonies (EEC). Some patients (8/28) 28.57% had mutations in VHL gene, out of which 3 novel homozygous missense mutations in exon 1 of VHL gene, p.Gly80Asp, p.Gln107Glu and p.Gln113Glu, were identified. In addition, (1/28) 3.5% patients had one reported heterozygous missense mutation in exon 12 of EPAS1 gene p.Gly537Arg and one novel frameshift mutation p.(Ala553Glyfs*58). Further, in silico analysis indicated most of the mutations, probably, were damaging the protein structures, causing the CE in these patients. In this study the mutations in EPO-R and EPAS1 genes were identified for the first time in India.

Pregnancy with Chuvash Polycythaemia and Other Congenital Erythrocytosis.

This original report describes the management of a pregnant woman with congenital erythrocytosis (Chuvash polycythaemia) and reviews the scarce data available in the literature. Therapy consisted of low-dose aspirin and phlebotomies to maintain haematocrit <50% while monitoring iron stores to avoid severe deficiency detrimental to the foetus. Despite normal initial foetal growth, the pregnancy was complicated by preterm birth due to chorioamnionitis. The placenta showed no signs of thrombotic events. The published reports cover 13 pregnancies in 8 patients, showing 1 first-trimester miscarriage, 5 infants with intrauterine growth restriction and/or preterm birth and 1 maternal thrombotic event. These cases were managed with phlebotomies, low-dose aspirin and/or low-molecular-weight heparin, although inconsistently.

A Kindred with a ß-Globin Base Substitution [ß89(F5)Ser→Arg (AGT>AGG); HBB: c.270T>G] Resulting in Hemoglobin Vanderbilt.

High oxygen affinity hemoglobins (Hbs), characterized by a decreased ability to release oxygen to the tissues and a left-shifted oxygen dissociation curve, are a rare cause of secondary erythrocytosis. Here, we report a base substitution in the ß-globin gene at codon 89 (AGT>AGG) in a kindred with familial erythrocytosis resulting in Hb Vanderbilt, a high oxygen affinity variant.