Primary Polycythemias Research Articles

Antipuritive Effect of Aqueous Root Extracts of Moringa oliefera on Alcohol-induced Haematoxicity in Wistar Rats

Aim: The study is aimed at investigating the antinutritive effects of aqueous root extract of Moringa oleifera on haematological indices following sub-chronic consumption of alcohol in Wistar rats.
 Methods and Materials: Thirty (30) experimental rats weighing 100-120 g were randomly divided into 6 groups of 5 rats each. Group 1, the normal control group was given just rat feed and water, group 2, negative control was administered alcohol only (1.5 ml/kg body weight), rats in group 3, 4 and 5 received combined administration of alcohol 1.5 ml/kg body weight and 200, 400 and 600 mg/kg body weight of aqueous root extract of Moringa oleifera respectively, group 6 rats were administered 250 mg/body weight of extract only. At the end of fourteen days (14) the experimental rats were then sacrificed, and blood was collected for haematological analysis.
 Results: The result obtained shows a dose-dependent response in almost all the parameters, white blood cell (WBC) count increases significantly(P<0.05) with 600 mg/kg while dose 200 mg/kg and 400 mg/g shows no significant change. Red blood cells (RBC) decreases non-significantly (P<0.05) with increased amount of aqueous Moringa root extract. Likewise, there was also a dose-dependent decrease in the haematological count and more noticeable with 200 mg/kg dose. It was also observed that mean corpuscular haemoglobin concentration (MCHC) and mean corpuscular volume (MCV) increases in all the treatment groups with significant observed in 400 mg/kg and 600 mg/kg. The increase in alcohol can bring about suppression of the blood cells production, enhance if there is reduction in the red blood cells, it, therefore, implies that the will be reduction in the oxygen-carrying capacity of the red blood cells, that would be carried to the tissues as well as the level of carbon dioxide returned to the lungs. Also, the PCV is involved in the transport of oxygen and absorption of the nutrient. Therefore, increase in PCV, shows a better transportation and thus results in an increase in both primary and secondary polycythemias.
 Conclusion: This research work shows that the plant extract contains some bioactive component or phytochemical constituents that are capable of ameliorating the toxicity effect of alcohol on animal models.

RUNX1 and NF-E2 Transcriptional Upregulation Is Not Specific For Myeloproliferative Neoplasms But Is Seen In Those Polycythemic Disorders With Augmented HIFs Signaling

▪RUNX1 and NF-E2 are transcription factors that regulate hematopoietic stem cell homeostasis. It has been reported that increased RUNX1 expression in the granulocytes is present in all three classical myeloproliferative neoplasms (MPN): polycythemia vera (PV), essential thrombocythemia and primary myelofibrosis (Wang et al, Blood 2010), and that elevated NF-E2 promotes erythropoietin (EPO)-independent erythroid maturation of hematopoietic stem cells in vitro (Bogeska et al, Stem Cells Transl Med 2013). A mouse model overexpressing the NF-E2 transgene in hematopoietic cells was reported to be a new model of myeloproliferative neoplasms (Kaufmann et al, J Exp Med 2012).Polycythemic states can be divided into primary polycythemias, characterized by intrinsically hyperproliferative erythroid progenitors that are hypersensitive to EPO, and secondary polycythemias, wherein erythroid progenitors respond normally to EPO but circulating EPO is elevated or inappropriately normal for the level of increased red cell mass. Some congenital disorders including those with mutations in the hypoxia sensing pathway may share features of both primary and secondary polycythemias. We considered the possibility that increased transcripts of RUNX1 and NF-E2 might be the feature of other primary polycythemic states as well.We report a study of 19 polycythemic patients with primary or secondary polycythemia with diverse etiologies including mutations in positive and negative regulators of hypoxia sensing pathway. RUNX1 and NF-E2 transcripts were quantitated in granulocytes and BFU-E colonies by qPCR. All primary polycythemic patients had erythroid progenitors hypersensitive to or independent to EPO; all secondary polycythemic subjects had normal erythroid progenitor response to EPO.RUNX1 and NF-E2 gene transcripts were increased in granulocytes and BFU-E colonies in all PV patients, two unrelated subjects with the VHLR200W homozygous mutation (Chuvash polycythemia), one polycythemic patient homozygous for the VHLP138L exon 2 mutation, and a patient with the HIF2αM535V gain-of-function mutation. We also found upregulated expression of RUNX1 and NF-E2 in granulocytes and BFU-Es from a polycythemic patient (with no detectable EPOR, JAK2V617F or JAK2 exon 12 mutations and low level of EPO < 1 mU/mL) who was heterozygous for a SNP in exon 3 (rs147341899) in the LNK gene. We examined transcripts of RUNX1 and NF-E2 genes in granulocytes from two Croatian polycythemic patients with a homozygous VHLH191D exon 3 mutation whose erythroid progenitors were not hypersensitive to EPO and whose RUNX1, but not NF-E2, transcript was increased. We found similar results in two compound heterozygotes for VHLT124A exon 2 and VHLL188V exon 3 mutations. These two polycythemic siblings had hypersensitive erythroid colonies, increased RUNX1 transcripts and decreased NF-E2 transcripts in granulocytes. RUNX1 and NF-E2 transcripts were normal in two subjects with primary polycythemia due to the EPOR gain-of-function EPORQ434Xmutation, and in five unrelated subjects with secondary polycythemia.We next examined granulocyte transcripts of HIF-regulated genes: TFRC, SLC2A1, VEGF, BNIP3 and HK1, and found them to be increased in all PV patients and all studied polycythemic patients with VHL, HIF2α or LNK mutations, but not in polycythemic EPORQ434Xpatients or five patients with secondary polycythemia. Increased transcripts of HIF regulated genes are compatible with the previously unappreciated Warburg effect in PV (see S. Sana's Abstract at this ASH meeting).We propose that increased expression of RUNX1 and NF-E2 is not specific for myeloproliferative neoplasms but also is not universal for primary polycythemic disorders. Therefore, increased expression of RUNX1 and NF-E2 do not seem to be underlying mechanism for MPNs development but rather represent factors associated with diverse primary polycythemia states with augmented HIF signaling.(Note: KK and LL contributed equally to this work.)This work was supported by 1P01CA108671-O1A2 (NCI) Myeloproliferative Disorders (MPD) Consortium (PI Ron Hoffman) project#1 (PI Prchal) and the Leukemia & Lymphoma Society. Work by KK, LL, MH and VD was in part supported by the European Structural Funds (project CZ.1.07/2.3.00/20.0164 and CZ.1.07/2.3.00/30.0041), grant LF_2013_010 and by Czech Science Foundation (Project-P301/12/1503). Disclosures:No relevant conflicts of interest to declare.

A Novel EPO Gene Mutation In a Family With Autosomal Dominant Polycythemia

Familial polycythemia/erythrocytosis (ECYT by OMIM), characterized by an absolute increase in red cell mass, is a heterogeneous group of disorders that can be attributed to either intrinsic erythroid progenitor defects, resulting in their hyperproliferation (primary polycythemias), or from circulating extracellular factors such as erythropoietin (EPO) stimulating erythropoiesis (secondary polycythemias). Known primary familial causes include gain-of-function EPO receptor gene mutations. Secondary polycythemia causes include gene mutations that increase hemoglobin oxygen affinity (a, b, and g globins and 2, 3 bisphosphoglycerate mutase, and cytochrome b5 reductase). Several mutations result in alterations of the hypoxia-sensing pathway, which is a primary regulator of EPO production, and familial polycythemia. These include gain-of-function mutations of the HIF-2-a gene (HIF2A), and loss-of-function mutations of two negative regulators of HIFs (EGLN1/PHD2) and von Hippel-Lindau (VHL) genes. Some of these mutations exhibit overlapping features of both primary and secondary polycythemias, such as Chuvash polycythemia. No mutations of the EPO gene have yet been reported.Here we report a 5-generation Caucasian family with autosomal dominant polycythemia. The propositus (III-11) was initially seen 28 years ago at the age of 2 years old. He had moderately increased EPO levels, no splenomegaly, and normal leukocyte and platelet numbers. He was not hypoxic and his hemoglobin oxygen dissociation (P50) was normal. His 21 family members agreed to be tested and 10 were polycythemic, while 11 were normal. Later linkage analyses of 18 re-consented relatives examined the association of a polycythemic phenotype with polymorphisms of HIF2A, HIF1A, EPOR, PHD2, and VHL genes, ruling these out as the cause. Exome sequencing of 5 affected individuals revealed a novel nucleotide change in chromosome 7 at -136nt upstream of the EPO gene (NG_021471 -136 G>A) from the ATG initiation site. This variant has not been reported in any publicly available genome databases and none of the 8 unrelated Caucasian controls have this variant. To determine the distribution of this variant and its segregation, we screened 7 affected and 8 unaffected relatives; all 8 unaffected samples were negative for this EPO variant, while all 7 affected individuals were heterozygous for this variant in the 5'UTR of the EPO gene.The effect(s) of this 5'UTR variant on EPO gene transcription is being examined by Luciferase assay, as well as in an expression assay using HEK293 EPO producing cells. In brief, constructs containing the -136nt variant having either the G (wild-type) or A (mutant) nucleotide of the EPO gene have been made and inserted into the pGL3 vector for the luciferase assay. EPO transcript quantitation studies will be carried out using human EPO cDNA clones with or without the -136nt variant transfected into HEK293 cell line and analyzed under two different conditions, ambient and at 5% oxygen. EPO expression levels under these two different conditions will be determined at multiple time points.This is the first report of an EPO gene mutation associated with familial polycythemia; its functional impact is being studied. Disclosures:No relevant conflicts of interest to declare.

The Clinical Utility Of Next-Generation Sequencing In The Diagnosis Of Polycythemia

Polycythemia or erythrocytosis is a disorder characterized by expansion of the RBC mass, and can be primary or secondary. Primary polycythemia is caused by an acquired or inherited mutation, it includes polycythemia vera and familial/congenital variants. e.g. due to gain of function mutations in the erythropoietin receptor (EPOR), or mutations in the hypoxia sensing pathway. Secondary polycythemia is caused by a circulating factor stimulating erythropoiesis, usually erythropoietin (EPO). It is most often due to an EPO response to hypoxia, but can also result from an EPO-secreting tumor. Either primary or secondary polycythemias can be inherited, i.e. due to germline mutations. The hypoxic response, mediated by hypoxia inducible transcription factors (HIFs), is central to the control and development of many essential biological functions, including erythropoiesis. Mutations in this pathway, causing polycythemia, have been identified in negative regulators of HIFs, such as the von Hippel-Lindau (VHL) gene, the HIF-prolyl-hydroxylase 2 (PHD2) gene, and gain-of-function mutations of the HIF-2-alpha (HIF2A) gene. Routine diagnostic testing can be challenging with specialized testing often only available in specialized research laboratories. Comprehensive, coding region analysis of all candidate genes by selective amplification of DNA regions of interest by PCR followed by the sequencing and analysis of amplified DNA fragments involved can be daunting due to molecular heterogeneity of causative genes as well as the size of the genes involved. Targeted molecular analysis is now being developed for both acquired (somatic) mutations or inherited (germline mutations) causing acquired and inherited diseases. We developed a novel, high-throughput, sensitive sequencing assay for diagnosis of congenital causes of polycythemias and polycythemia vera. Our diagnostic panel includes 9 genes and covers the complete coding region, splice site junctions, and, where appropriate, deep intronic or regulatory regions. Custom targeted gene capture and library construction for next-generation sequencing (NGS) was performed using HaloPlex as described by the manufacturer (Agilent Technologies, Santa Clara, CA). One hundred base-pair paired-end sequencing was done on a HiSeq 2000 system (Illumina, San Diego, CA). Bioinformatic analysis was based on an “in house” pipeline using standard open-source software. A total of 10 patients with clinically suspected polycythemia, and 30 normal controls were tested in our assay. Whole blood genomic DNA was isolated from the patients and targeted gene capture performed. Mutations in the target genes were identified in 3/10 patients, two of these being novel. All identified mutations were confirmed by Sanger sequencing. In one of these patients, a child with increased RBC mass, with EPO hypersensitive BFU-E colonies, a novel pathogenic, nonsense mutation was found in exon 8 of the EPOR gene (Q434X) resulting protein truncation and absence of the C-terminal negative regulatory domain of the receptor. In a different patient with suspected primary congenital/familial polycythemia due to EPO hypersensitive BFU-E colonies, we identified a novel pathogenic mutation in exon 3 of the MPL gene. This novel mutation, a single base deletion causes a frame-shift in codon 126 (F126L) and early termination at codon 130. To the best of our knowledge, this is the first report of a loss of function mutation in the MPL gene in a patient with polycythemia. Analysis of greater cohort of polycythemic patients is now in progress. Disclosures:No relevant conflicts of interest to declare.

Novel Homozygous VHL Mutation in Exon 2 (413C>T:P138L) Is Associated with Congenital Polycythemia, Elevated Level of RUNX1/AML1 Transcript, but Not with the Cancer.

Abstract 2081There are two known homozygous VHL gene mutations causing polycythemia that are not associated with a VHL cancer syndrome - an R200W mutation endemic in Chuvashia causing the first recognized disorder of augmented hypoxia sensing in normoxia, and an H191D mutation of Croatian origin. Both are located in the distal exon 3 of the VHL gene on its C-terminal domain. As different positions of loss-of-function mutations of VHL gene are associated with different type of cancers, it has been proposed that only C-terminal domain VHL mutations would cause polycythemia. However, we now contradict this notion. We report a novel homozygous variant of the VHL gene located in the middle of coding region in exon 2; 413C>T:P138L. The propositus is a 15 year old Punjabi female with congenital polycythemia; i.e. elevated erythropoietin (EPO) 40 mIU/mL, no JAK2 mutations, and hemoglobin 19–20 g/dl. Her parents are VHL P138L heterozygotes and no VHL tumors are reported in the extended family, in contrast to the other VHL P138 residue (P138R, P138T) mutations that have been reported in VHL syndrome and renal cancer.pVHL is a negative regulator of hypoxia inducible transcription factors (HIFs) as it degrades a subunits of HIFs. It has been proposed, that an association between mutated pVHL and suppressor of cytokine signaling 1 (SOCS1) leads to JAK2 up-regulation and enhanced erythropoiesis. We show that the VHL P138L mutation, which lies in the catalytic HIF-1a peptide ligand-binding region, perturbs pHIF-1a pVHL interaction due to a conformational effect on the W117 and S111 residues lying within 2.8 to 4.3 Å distance from the mutated L138. The effect of this single mutation on overall structure is a shift of 1.9 Å RMSD (root mean square deviation) from the wild-type complex structure. Molecular dynamics simulations also found that the VHL P138L mutation can affect the binding of SOCS1 protein to the pVHL groove due to a strong steric effect of T124, H125 and D126 residues located close to the C-terminal pVHL. The accumulation of HIFs and up-regulated transcription of downstream target genes including those for glucose transporter-1 (SLC2A1) and transferrin (TF) were found in the propositus’ granulocytes.We then analyzed the VHL P138L propositus and her heterozygous parents' erythroid progenitors and found them to be hypersensitive to EPO (a feature of primary polycythemias without EPO independent colonies). Because of reports that RUNX1/AML1 transcript levels are specifically upregulated in erythroid progenitors in polycythemia vera (PV) and allegedly responsible for PV EPO hypersensitivity, we analyzed erythroid RUNX1/AML1 transcripts in the propositus and her parents and found it increased.We demonstrate that a homozygous mutation in exon 2 of the VHL gene can also be associated with a polycythemic phenotype rather than VHL syndrome tumors. Further, we report that increased levels of RUNX1/AML1 transcripts are not specific for PV but can be seen in other primary polycythemias. Disclosures:No relevant conflicts of interest to declare.

Oxygen Sensing-From Bedside to Bench: A Family with Erythrocytosis Establishes a Role for Prolyl Hydroxylase Domain Protein 2 in Oxygen Homeostasis. Proc National Acad Sci U S A 103: 654-659, 2006.

Oxygen Sensing-From Bedside to Bench: A Family with Erythrocytosis Establishes a Role for Prolyl Hydroxylase Domain Protein 2 in Oxygen Homeostasis. Proc National Acad Sci U S A 103: 654-659, 2006.

Polycythemia vera and other primary polycythemias

Diagnosis and therapy of polycythemia vera are controversial since the molecular basis of polycythemia vera remains unknown. Distinguishing between polycythemia vera and other polycythemic disorders can be very challenging. The purpose of this review is to discuss the recent progress in this area and critically review the published data in context of our knowledge of other polycythemic disorders. Erythropoietin is the principal regulator of regulator of erythropoiesis; its production is regulated by the degree of hypoxia. Our knowledge of cellular responses to hypoxia has recently exploded and led to the elucidation of the molecular basis of a polycythemia caused by augmentation of hypoxic sensing, Chuvash polycythemia. Similar progress in understanding the molecular basis of polycythemia vera has been elusive. A simple, readily available laboratory test to establish a diagnosis of polycythemia vera would be highly desirable; however, none exists. The value of quantization of neutrophil PRV-1 mRNA, platelet c-mpl expression, in vitro assays of erythroid progenitor cells, serum erythropoietin levels, establishing clonality in female subjects using assays employing X-chromosome-based polymorphism assays, and the progress in the chromosomal location of the gene is discussed. Integration of this information underlies the complexity of the molecular biology of polycythemia vera and indicates likely interaction of multiple genetic events in the genesis of polycythemia vera. The existence of family clustering of PV may facilitate the search for PV molecular basis. Only collaborative interaction of clinical researchers and laboratory scientists will lead to meaningful progress in determining the molecular basis of PV.

Polycythemia and oxygen sensing

Polycythemias can be differentiated based on the responsiveness of erythroid progenitors to circulating cytokines. Primary polycythemias are characterized by an augmented response due to acquired somatic or inherited germ-line mutations that are expressed within hematopoietic progenitors causing increased proliferation or decreased apoptosis and resulting in accumulation of red blood cells. In terms of oxygen requirements, primary polycythemias can be viewed as the production of hemoglobin fully dissociated from the tissue oxygen needs and from the oxygen sensing pathway. Polycythemia vera (PV) is the most common primary polycythemia. PV bone marrow progenitors cells can form erythroid colonies in the absence of exogenous erythropoietin in vitro. These endogenous erythroid colonies (EEC) are useful in differentiating PV and secondary polycythemias. They also can differentiate PV where this feature is independent of Epo signalling from primary familial and congenital polycythemia. In this autosomal dominant primary polycythemia, at variance with PV, EEC formation is abolished by anti-Epo and anti-Epo receptor neutralising antibodies. Mutations of the EPOR have been described and resulted in nine cases in truncated EPORs lacking the cytoplasmic carboxy-terminal of the receptor which possesses a negative growth regulatory domain. However, recent data suggest that different mutations may cause PFCP in most cases. Secondary polycythemia can be viewed as either physiological response to satisfy the oxygen needs of the tissues, resulting for instance from high affinity hemoglobins or BPG mutase deficiency, or as the result of germ-line or somatic mutations disturbing the oxygen sensing pathway or its target: Epo. Chuvash polycythemia is a frequently symptomatic disorder with an autosomal recessive inheritance and inappropriately high Epo levels. The erythroid progenitors are hypersensitive to Epo linking this condition to both primary and secondary polycythemia. A germline missense mutation at nucleotide 598 in both alleles of the von Hippel–Lindau gene results in increased hypoxia inducible factor-1 (HIF-1) expression in normoxic conditions. HIF-1 controls the expression of many genes including Epo. Identifying causal defects in other situations like post-renal transplant erythrocytosis and cases of autosomal dominant polycythemia with high Epo levels will help further understanding of the regulation of erythropoiesis.

Les polyglobulies héréditaires

Purpose. – The majority of polycythemias occurs sporadically without any other familial case. Very occasionally polycythemia finds a familial support. This work is a review of the actual knowledge about inherited polycythemias. Current knowledge and key points. – Although polycythemias linked to a anomaly of the haemoglobin affinity for oxygen are well understood (haemoglobin mutants with high oxygen affinity, 2-3 Diphosphoglycerate deficiency and methemoglobinemia), so called primary polycythemias (above all primary familial and congenital polycythemias) just begin to find an explanation for ten years (erythropoietin receptor gene mutation). Future prospects and projects. – Progressively, the part of really idiopathic polycythemias is smaller and smaller. Although most of mechanisms to explain congenital polycythemias are understood, some of them are still unresolved (Chuvash polycythemia, the majority of primary familial and congenital polycythemias).

Molecular biology of polycythemias.

Polycythemia is literally translated as "many cells in the blood". Only erythrocytosis (an alternative term for these disorders) produces polycythemia since leukocytes and platelets are present in blood in far smaller proportions. Polycythemia may be due to increased proliferation or decreased apoptosis of erythroid progenitors, or to delayed erythroid differentiation with an increased number of progenitor cell divisions. Prolonged red cell survival, another theoretical cause of polycythemia, has not yet been described and with intact regulatory mechanisms is unlikely to occur. Primary polycythemias result from abnormalities expressed in hematopoietic progenitors. In contrast, circulating factors cause secondary polycythemia (1). There are acquired and congenital causes of both primary and secondary polycythemia (1).

Congenital and inherited polycythemia.

Absolute polycythemia is a condition with increased red blood cell mass. There are a number of primary and secondary polycythemic disorders leading to absolute polycythemia. Primary polycythemias are caused by a defect intrinsic to the erythroid progenitor cells. The best characterized primary polycythemia is the autosomal dominant primary familial and congenital polycythemia (PFCP). Familial or childhood occurrence of the myeloproliferative disorder polycythemia vera are also discussed, emphasizing the importance of distinction between polycythemia vera and PFCP. Congenital or familial secondary polycythemic conditions are characterized by increased red cell mass, which is caused by circulating serum factors, typically erythropoietin.

Signal Transduction in the Erythropoietin Receptor System

Events relayed via the single transmembrane receptor for erythropoietin (Epo) are essential for the development of committed erythroid progenitor cells beyond the colony-forming unit–erythroid stage, and this clearly involves Epo's inhibition of programmed cell death (PCD). Less well resolved, however, are issues regarding the precise nature of Epo-dependent antiapoptotic mechanisms, the extent to which Epo might also promote mitogenesis and/or terminal erythroid differentiation, and the essential vs modulatory nature of certain Epo receptor cytoplasmic subdomains, signal transducing factors, and downstream pathways. Accordingly, this review focuses on the following aspects of Epo signal transduction: (1) Epo receptor/Jak2 activation mechanisms; (2) the critical vs dispensable nature of (P)Y sites and SH2 domain-encoding effectors in survival, growth, and differentiation responses; (3) primary mechanisms by which Epo inhibits PCD; (4) the integration of signals relayed by coexpressed and possibly directly interacting cytokine receptors; and (5) predictions regarding effector function which are provided by the association of certain primary and familial polycythemias with mutated human Epo receptor forms.

Molecular basis for polycythemia.

This overview concentrates on familial and congenital polycythemias in the context of other polycythemic disorders, with emphasis on those with established molecular lesions. Recent advances in the regulation of erythropoiesis, as they may relate to polycythemic states, are discussed as a background for those well-defined polycythemic states wherein the molecular defect has not yet been elucidated. Primary familial congenital polycythemias and congenital and familial secondary polycythemias, including hemoglobin mutants, methemoglobinemias and congenital 2,3-bisphosphoglycerate deficiency, are discussed. The most common primary polycythemia, polycythemia vera, as well as the only likely endemic congenital secondary polycythemia, known as Chuvash polycythemia, are discussed.

Two New EPO Receptor Mutations: Truncated EPO Receptors Are Most Frequently Associated With Primary Familial and Congenital Polycythemias

AbstractPrimary polycythemias are caused by an acquired or inborn mutation affecting hematopoietic/erythroid progenitors that results in an abnormal response to hematopoietic cytokines. Primary familial and congenital polycythemia (PFCP; also known as familial erythrocytosis) is characterized by elevated red blood cell mass, low serum erythropoietin (EPO) level, normal oxygen affinity of hemoglobin, and typically autosomal dominant inheritance. In this study we screened for mutations in the cytoplasmic domain of the EPO receptor (EPOR; exons 7 and 8 of the EPOR gene) in 27 unrelated subjects with primary or unidentified polycythemia. Two new EPOR mutations were found, which lead to truncation of the EPOR similarly to previously described mutations in PFCP subjects. The first is a 7-bp deletion (del59855991) found in a Caucasian family from Ohio. The second mutation (5967insT) was found in a Caucasian family from the Czech Republic. In both cases the EPO dose responses of the erythroid progenitors of the affected subjects were examined to confirm the diagnosis of PFCP. In one of these families, the in vitro behavior of erythroid progenitors in serum-containing cultures without the addition of EPO mimicked the behavior of polycythemia vera progenitors; however, we show that antibodies against either EPO or the EPOR distinguish the in vitro growth abnormality of polycythemia vera erythroid progenitors from that seen in this particular PFCP family. We conclude that PFCP is a disorder that appears to be associated in some families with EPOR mutations. So far, most of the described EPOR mutations (6 out of 8) associated with PFCP result in an absence of the C-terminal negative regulatory domain of the receptor.

“Benign erythrocytosis” and other familial and congenital polycythemias

The term familial and congenital polycythemia encompasses a heterogeneous group of disorders with the common characteristic of an absolute increased red cell mass since birth and/or similar phenotype also present in relatives. In the last 2 decades the differential diagnosis between primary and secondary familial polycythemias became more physiologically relevant as new sensitive techniques, such as accurate measurements of serum erythropoietin (S-EPO) concentration by radioimmunoassay (RIA) or ELISA, and assessment of growth of erythroid progenitor cells in vitro became available. Consequently, correct classification of many older previous reports of familial polycythemias is difficult. While familial secondary polycythemias due to high oxygen affinity hemoglobin mutants are not infrequent and have been well delineated in terms of molecular pathophysiology and phenotype during the last 3 decades, those secondary familial polycythemias due to 2,3 DPG deficiency are very rare. Familial and congenital polycythemias with increased EPO concentration and normal arterial oxygen saturation and oxygen dissociation kinetics represent an intriguing group of disorders wherein the molecular lesions remain obscure; however, in some instances a possibility of abnormal oxygen sensing pathway involving hypoxia inducible factor-1 (HIF-1) open an intriguing yet unexplored area of hematology and biology. In contrast the primary familial and congenital polycythemia (PFCP) has been only recently recognized (the first report published in 1977). Various designations have been used in the past to describe PFCP, a rare clinical syndrome, including: benign familial erythrocytosis, polycythemia vera of childhood, primary polycythemia, pure erythrocytosis, etc. Some of these terms stressed the relatively benign, non-progressive course of the disease with a normal lifespan of affected subjects; however, the apparent benignity of some of these disorders has been questioned. These disorders are familial and/or congenital, and the clinical and laboratory evidence of secondary polycythemias must be excluded. Only about 2 dozen familial and sporadic cases with PFCP have been reported. However, the mutations of erythropoietin receptor (EPOR) found in some of families with PFCP represent the only defined molecular defect of primary polycythemic phenotypes. All reported PFCP associated EPOR mutations result in truncation of its intracytoplasmic C-terminal domain which negatively regulates the EPO/EPOR signal transduction pathway. Subjects with these mutations have decreased or normal S-EPO and increased sensitivity of erythroid progenitor cells to low EPO concentrations in in vitro assays. Mutations of other genes involved in post EPOR signaling pathway such as JAK-2, HCP and STAT 5 may also play a causative role in pathogenesis of some of PFCP families where mutation of EPOR was not found.

Primary polycythemias.

In this review, primary polycythemic states are discussed in the context of other polycythemic disorders. Primary polycythemias result from an acquired or inborn mutation affecting hematopoietic and erythroid cells. The best-known type of primary polycythemia is polycythemia vera, which is caused by an acquired somatic mutation of a hematopoietic stem cell with exaggerated myeloid proliferation; the molecular events leading to this disease are not understood. In contrast, primary familial and congenital polycythemias result from inborn mutation affecting hematopoietic and erythroid cells. The molecular mechanisms causing primary familial and congenital polycythemias may be different in different families; some have already been defined. Progress in defining the molecular defect of primary polycythemias and the better understanding of altered signal transduction leading to excessive erythrocyte production should provide important insights into the pathogenesis of primary polycythemias, other leukemic disorders, as well as normal hematopoiesis. Such information should contribute to better understanding of and more effective therapeutic interventions in myeloproliferative and leukemic disorders.

The Effect of Iron Stores on Ferrokinetics in Polycythemia.

Excerpt Ferrokinetics have been used to differentiate primary, secondary, and relative polycythemias. Since the differences in ferrokinetics might be explained by the consistently depleted iron sto...