Clinical aspects and pathogenesis of congenital dyserythropoietic anemias: from morphology to molecular approach

Identification of a novel splice variant in SEC23B gene in a patient with concomitant presence of congenital dyserythropoietic anemia II and Gilbert's syndrome

BACKGROUND

Congenital dyserythropoietic anemia Ⅱ (CDA Ⅱ) is a rare inherited disorder of defective erythropoiesis caused by SEC23B gene mutation. CDA Ⅱ is often misdiagnosed as a more common type of clinically related anemia, or it remains undiagnosed due to phenotypic variability caused by the coexistence of inherited liver diseases, including Gilbert's syndrome (GS) and hereditary hemochromatosis.

METHODS

We describe the case of a boy with genetically undetermined severe hemolytic anemia, hepatosplenomegaly, and gallstones whose diagnosis was achieved by targeted next generation sequencing.

RESULTS

Molecular analysis revealed a maternally inherited novel intronic variant and a paternally inherited missense variant, c.[994-3C > T];[1831C > T] in the SEC23B gene, confirming diagnosis of CDA Ⅱ. cDNA analysis verified that the splice acceptor site variant results in two mutant transcripts, one with an exon 9 skip and one in which exons 9 and 10 are deleted. SEC23B mRNA levels in the patient were lower than those in healthy controls. The patient was also homozygous for the UGT1A1*6 allele, consistent with GS.

CONCLUSION

Identification of the novel splice variant in this study further expands the spectrum of known SEC23B gene mutations. Molecular genetic approaches can lead to accurate diagnosis and management of CDA Ⅱ patients, particularly for those with GS coexisting.

Trans-acting genetic modifiers of clinical severity in heterozygous β-Thalassemia trait

There is a group of beta (β)-thalassemia trait 'carriers' (with heterozygous mutations) who should be asymptomatic with minor abnormalities in their hematological parameters, but experience more severe disease manifestations than predicted based solely on their β-globin genotype. This review focuses on literature describing trans-acting genetic modifiers outside of the α- and β-globin gene clusters that could cause this phenomenon. These genetic modifiers are categorized into: mutations affecting the quantity of alpha-globin products, non-globin mutations affecting erythropoiesis, membranopathies, enzymopathies and erythrocyte-independent modifiers of complications relating to β-thalassemia. Although some genetic determinants seem to correlate more directly with β-thalassemia trait severity, such as mutations in SUPT5H, PIEZO1 and hereditary elliptocytosis, the difficulties of linking the contribution of other modulating factors are elucidated in this review. Targeted next generation sequencing of hemolytic anemias can be helpful but also raises another quandary in interpreting variants of uncertain significance. The accrual of knowledge, along with the increased availability of genetic testing for genetic modifiers has considerable potential for clinical applications such as genetic counselling, decision-making for clinical interventions and prognostication, and perhaps generating new therapeutic targets.

Updates on clinical and laboratory aspects of hereditary dyserythropoietic anemias

Hereditary dyserythropoietic anemias, or congenital dyserythropoietic anemias (CDAs), are rare disorders disrupting normal erythroid lineage development, resulting in ineffective erythropoiesis and monolinear cytopenia. CDAs include three main types (I, II, III), transcription-factor-related forms, and syndromic forms. The widespread use of next-generation sequencing in the last decade has unveiled novel causative genes and unexpected genotype-phenotype correlations. The discovery of the genetic defects underlying the CDAs not only facilitates accurate diagnosis but also enhances understanding of CDA pathophysiology. Notable advancements include identifying a hepatic-specific role of the SEC23B loss-of-function in iron metabolism dysregulation in CDA II, deepening CDIN1 dysfunction during erythroid differentiation, and uncovering a recessive CDA III form associated with RACGAP1 variants. Current treatments primarily rely on supportive measures tailored to disease severity and clinical features. Comparative studies with pyruvate kinase deficiency have illuminated new therapeutic avenues by elucidating iron dyshomeostasis and dyserythropoiesis mechanisms. We herein discuss recent progress in diagnostic methodologies, novel gene discoveries, and enhanced comprehension of CDA pathogenesis and molecular genetics.

Designing a single-arm phase 2 clinical trial of mitapivat for adult patients with erythrocyte membranopathies (SATISFY): a framework for interventional trials in rare anaemias - pilot study protocol

INTRODUCTION

Membranopathies encompass haemolytic disorders arising from genetic variants in erythrocyte membrane proteins, including hereditary spherocytosis and stomatocytosis. Congenital dyserythropoietic anaemia type II (CDA II) is associated with the SEC23B gene and can exhibit phenotypic similarities to membranopathies. Current treatment options for these conditions, apart from splenectomy, are primarily supportive. Mitapivat, a novel pyruvate kinase (PK) activator, has demonstrated efficacy in increasing haemoglobin levels and reducing haemolysis in patients with PK deficiency, thalassemia, sickle cell disease and a mouse model of hereditary spherocytosis.

METHODS AND ANALYSES

Safety and efficacy of mitapivat sulfate in adult patients with erythrocyte membranopathies (SATISFY) is a prospective, multicentre, single-arm phase two trial involving approximately 25 adult patients (≥18 years) diagnosed with a membranopathy or CDA II. During the 8-week dose escalation period, subjects will receive an initial dose of 50 mg mitapivat two times per day and may increase to 100 mg two times per day at week 4 based on the safety and changes in haemoglobin levels. Patients tolerating mitapivat well may be eligible to continue in two consecutive 24-week fixed dose periods.The primary objective of this study is to evaluate the safety of mitapivat, assessed through the occurrence of treatment-emergent adverse events. Secondary objectives include assessing the effects of mitapivat on haemoglobin levels, haemolysis, erythropoiesis, patient-reported outcome measures and spleen size.SATISFY aims to assess the safety and efficacy of mitapivat in adult patients with red blood cell membranopathies and CDA II, with the aim of establishing proof-of-concept in patients living with these rare conditions.

ETHICS AND DISSEMINATION

NCT05935202/CTIS:2023-503271-24-01. Findings will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

Clinicaltrials.gov, NCT05935202. CTIS:2023-503271-24-01. Registered 07-July-2023. Protocol number: 2.1. https://clinicaltrials.gov/study/NCT05935202.

New Cases and Mutations in SEC23B Gene Causing Congenital Dyserythropoietic Anemia Type II

Congenital dyserythropoietic anemia type II (CDA II) is an inherited autosomal recessive blood disorder which belongs to the wide group of ineffective erythropoiesis conditions. It is characterized by mild to severe normocytic anemia, jaundice, and splenomegaly owing to the hemolytic component. This often leads to liver iron overload and gallstones. CDA II is caused by biallelic mutations in the SEC23B gene. In this study, we report 9 new CDA II cases and identify 16 pathogenic variants, 6 of which are novel. The newly reported variants in SEC23B include three missenses (p.Thr445Arg, p.Tyr579Cys, and p.Arg701His), one frameshift (p.Asp693GlyfsTer2), and two splicing variants (c.1512-2A>G, and the complex intronic variant c.1512-3delinsTT linked to c.1512-16_1512-7delACTCTGGAAT in the same allele). Computational analyses of the missense variants indicated a loss of key residue interactions within the beta sheet and the helical and gelsolin domains, respectively. Analysis of SEC23B protein levels done in patient-derived lymphoblastoid cell lines (LCLs) showed a significant decrease in SEC23B protein expression, in the absence of SEC23A compensation. Reduced SEC23B mRNA expression was only detected in two probands carrying nonsense and frameshift variants; the remaining patients showed either higher gene expression levels or no expression changes at all. The skipping of exons 13 and 14 in the newly reported complex variant c.1512-3delinsTT/c.1512-16_1512-7delACTCTGGAAT results in a shorter protein isoform, as assessed by RT-PCR followed by Sanger sequencing. In this work, we summarize a comprehensive spectrum of SEC23B variants, describe nine new CDA II cases accounting for six previously unreported variants, and discuss innovative therapeutic approaches for CDA II.

Congenital dyserythropoietic anaemia type II in a teenager presenting with severe anaemia

Congenital dyserythropoietic anaemia (CDA) type II is a rare disease characterised by inefficient erythropoiesis and mononuclear cytopenia. Patients generally present with extravascular haemolytic anaemia, jaundice and splenomegaly. A female patient in her mid-teens presented with severe anaemia and abdominal distention. Medical history was significant for the diagnosis of β-thalassaemia intermedia made in her infancy. However, subsequent investigations showed normal reticulocyte counts that were disproportionate to the severity of her anaemia and a negative β-thalassemia mutation analysis, leading to concerns about a specific lineage disorder. A bone marrow trephine showed features typical of CDA type II-erythroid hyperplasia with multiple binucleate erythrocytes. CDA type II has often been mistaken for other congenital or acquired forms of anaemia; this case report intends to raise awareness among clinicians to consider CDA type II as a rare but possible cause of severe anaemia in a teenager with a previous presumptive diagnosis of β-thalassaemia .

SEC23B Loss-of-Function Suppresses Hepcidin Expression by Impairing Glycosylation Pathway in Human Hepatic Cells

Biallelic pathogenic variants in the SEC23B gene cause congenital dyserythropoietic anemia type II (CDA II), a rare hereditary disorder hallmarked by ineffective erythropoiesis, hemolysis, erythroblast morphological abnormalities, and hypo-glycosylation of some red blood cell membrane proteins. Abnormalities in SEC23B, which encodes the homonymous cytoplasmic COPII (coat protein complex II) component, disturb the endoplasmic reticulum to Golgi trafficking and affect different glycosylation pathways. The most harmful complication of CDA II is the severe iron overload. Within our case series (28 CDA II patients), approximately 36% of them exhibit severe iron overload despite mild degree of anemia and slightly increased levels of ERFE (the only erythroid regulator of hepcidin suppression). Thus, we hypothesized a direct role of SEC23B loss-of-function in the pathomechanism of hepatic iron overload. We established a hepatic cell line, HuH7, stably silenced for SEC23B. In silenced cells, we observed significant alterations of the iron status, due to both the alteration in BMP/SMADs pathway effectors and a reduced capability to sense BMP6 stimulus. We demonstrated that the loss-of-function of SEC23B is responsible of the impairment in glycosylation of the membrane proteins involved in the activation of the BMP/SMADs pathway with subsequent hepcidin suppression. Most of these data were confirmed in another hepatic cell line, HepG2, stably silenced for SEC23B. Our findings suggested that the pathogenic mechanism of iron overload in CDA II is associated to both ineffective erythropoiesis and to a specific involvement of SEC23B pathogenic variants at hepatic level. Finally, we demonstrated the ability of SEC23B paralog, i.e., SEC23A, to rescue the hepcidin suppression, highlighting the functional overlap between the two SEC23 paralogs in human hepatic cells.

The Role of Gene Variants in the Iron Metabolism of Anemic Adolescent Girls

Background and objectives Iron deficiency anemia (IDA) and the role of genetic variants in determining the iron status in adolescent girls are not yet well-understood. This study aims to investigate the association of the rs602662, rs1049296, rs1805051, rs855791, rs224589, and rs11568350 genes with IDA and iron bio-status parameters. Methods This study consisted of 132 patients (IDA group) and 110 healthy controls. The genotype was analyzed through polymerase chain reaction-restriction fragment length polymorphism. Results No differences were noted in the distribution of genotype and allele frequency single nucleotide polymorphism between the IDA and control group. In the IDA group, the GA carriers of rs602662 had a higher hemoglobin concentration (P=0.02) and packed cell volume (P=0.007), whereas transferrin saturation was increased in AA (P=0.02). The genetic variants rs1049296, rs1805051, rs224589, and rs855791 had a non-statistical significance on hematological parameters. Both the GT and TT carriers of the rs11568350 gene showed a low hemoglobin concentration (P=0.02 and <0.001) and mean corpuscular hemoglobin in GT carrier (P=0.01), whereas the TT risk of this gene showed a decreased packed cell volume (P=0.01). In the control patients, no association was observed with serum iron and hematological parameters. Conclusion Of these genetic variants, the GG and GA genotype frequency in rs602662 and the GG, GT, and TT in rs11568350 were associated with low iron status in anemic patients compared to the control patients.

Confounding factors in the diagnosis and clinical course of rare congenital hemolytic anemias

Congenital hemolytic anemias (CHAs) comprise defects of the erythrocyte membrane proteins and of red blood cell enzymes metabolism, along with alterations of erythropoiesis. These rare and heterogeneous conditions may generate several difficulties from the diagnostic point of view. Membrane defects include hereditary spherocytosis and elliptocytosis, and the group of hereditary stomatocytosis; glucose-6-phosphate dehydrogenase and pyruvate kinase, are the most common enzyme deficiencies. Among ultra-rare forms, it is worth reminding other enzyme defects (glucosephosphate isomerase, phosphofructokinase, adenylate kinase, triosephosphate isomerase, phosphoglycerate kinase, hexokinase, and pyrimidine 5′-nucleotidase), and congenital dyserythropoietic anemias. Family history, clinical findings (anemia, hemolysis, splenomegaly, gallstones, and iron overload), red cells morphology, and biochemical tests are well recognized diagnostic tools. Molecular findings are increasingly used, particularly in recessive and de novo cases, and may be fundamental in unraveling the diagnosis. Notably, several confounders may further challenge the diagnostic workup, including concomitant blood loss, nutrients deficiency, alterations of hemolytic markers due to other causes (alloimmunization, infectious agents, rare metabolic disorders), coexistence of other hemolytic disorders (autoimmune hemolytic anemia, paroxysmal nocturnal hemoglobinuria, etc.). Additional factors to be considered are the possible association with bone marrow, renal or hepatic diseases, other causes of iron overload (hereditary hemochromatosis, hemoglobinopathies, metabolic diseases), and the presence of extra-hematological signs/symptoms. In this review we provide some instructive clinical vignettes that highlight the difficulties and confounders encountered in the diagnosis and clinical management of CHAs.

Severe Presentation of Congenital Hemolytic Anemias in the Neonatal Age: Diagnostic and Therapeutic Issues

Congenital hemolytic anemias (CHAs) are a group of diseases characterized by premature destruction of erythrocytes as a consequence of intrinsic red blood cells abnormalities. Suggestive features of CHAs are anemia and hemolysis, with high reticulocyte count, unconjugated hyperbilirubinemia, increased lactate dehydrogenase (LDH), and reduced haptoglobin. The peripheral blood smear can help the differential diagnosis. In this review, we discuss the clinical management of severe CHAs presenting early on in the neonatal period. Appropriate knowledge and a high index of suspicion are crucial for a timely differential diagnosis and management. Here, we provide an overview of the most common conditions, such as glucose-6-phosphate dehydrogenase deficiency, pyruvate kinase deficiency, and hereditary spherocytosis. Although rare, congenital dyserythropoietic anemias are included as they may be suspected in early life, while hemoglobinopathies will not be discussed, as they usually manifest at a later age, when fetal hemoglobin (HbF) is replaced by the adult form (HbA).

Congenital dyserythropoietic anemias

Congenital dyserythropoietic anemias (CDAs) are a heterogeneous group of inherited anemias that affect the normal differentiation-proliferation pathways of the erythroid lineage. They belong to the wide group of ineffective erythropoiesis conditions that mainly result in monolinear cytopenia. CDAs are classified into the 3 major types (I, II, III), plus the transcription factor-related CDAs, and the CDA variants, on the basis of the distinctive morphological, clinical, and genetic features. Next-generation sequencing has revolutionized the field of diagnosis of and research into CDAs, with reduced time to diagnosis, and ameliorated differential diagnosis in terms of identification of new causative/modifier genes and polygenic conditions. The main improvements regarding CDAs have been in the study of iron metabolism in CDAII. The erythroblast-derived hormone erythroferrone specifically inhibits hepcidin production, and its role in the mediation of hepatic iron overload has been dissected out. We discuss here the most recent advances in this field regarding the molecular genetics and pathogenic mechanisms of CDAs, through an analysis of the clinical and molecular classifications, and the complications and clinical management of patients. We summarize also the main cellular and animal models developed to date and the possible future therapies.

Genetic and functional insights into CDA-I prevalence and pathogenesis

BACKGROUND

Congenital dyserythropoietic anaemia type I (CDA-I) is a hereditary anaemia caused by biallelic mutations in the widely expressed genes CDAN1 and C15orf41. Little is understood about either protein and it is unclear in which cellular pathways they participate.

METHODS

Genetic analysis of a cohort of patients with CDA-I identifies novel pathogenic variants in both known causative genes. We analyse the mutation distribution and the predicted structural positioning of amino acids affected in Codanin-1, the protein encoded by CDAN1. Using western blotting, immunoprecipitation and immunofluorescence, we determine the effect of particular mutations on both proteins and interrogate protein interaction, stability and subcellular localisation.

RESULTS

We identify six novel CDAN1 mutations and one novel mutation in C15orf41 and uncover evidence of further genetic heterogeneity in CDA-I. Additionally, population genetics suggests that CDA-I is more common than currently predicted. Mutations are enriched in six clusters in Codanin-1 and tend to affect buried residues. Many missense and in-frame mutations do not destabilise the entire protein. Rather C15orf41 relies on Codanin-1 for stability and both proteins, which are enriched in the nucleolus, interact to form an obligate complex in cells.

CONCLUSION

Stability and interaction data suggest that C15orf41 may be the key determinant of CDA-I and offer insight into the mechanism underlying this disease. Both proteins share a common pathway likely to be present in a wide variety of cell types; however, nucleolar enrichment may provide a clue as to the erythroid specific nature of CDA-I. The surprisingly high predicted incidence of CDA-I suggests that better ascertainment would lead to improved patient care.

The Interplay between Drivers of Erythropoiesis and Iron Homeostasis in Rare Hereditary Anemias: Tipping the Balance

Rare hereditary anemias (RHA) represent a group of disorders characterized by either impaired production of erythrocytes or decreased survival (i.e., hemolysis). In RHA, the regulation of iron metabolism and erythropoiesis is often disturbed, leading to iron overload or worsening of chronic anemia due to unavailability of iron for erythropoiesis. Whereas iron overload generally is a well-recognized complication in patients requiring regular blood transfusions, it is also a significant problem in a large proportion of patients with RHA that are not transfusion dependent. This indicates that RHA share disease-specific defects in erythroid development that are linked to intrinsic defects in iron metabolism. In this review, we discuss the key regulators involved in the interplay between iron and erythropoiesis and their importance in the spectrum of RHA.

Congenital dyserythropoietic anemia type I: First report from the Congenital Dyserythropoietic Anemia Registry of North America (CDAR)

Congenital dyserythropoietic anemias (CDAs) are characterized by ineffective erythropoiesis and distinctive erythroblast abnormalities; the diagnosis is often missed or delayed due to significant phenotypic heterogeneity. We established the CDA Registry of North America (CDAR) to study the natural history of CDA and create a biorepository to investigate the pathobiology of this heterogeneous disease. Seven of 47 patients enrolled so far in CDAR have CDA-I due to biallelic CDAN1 mutations. They all presented with perinatal anemia and required transfusions during infancy. Anemia spontaneously improved during infancy in three patients; two became transfusion-independent rapidly after starting interferon-α₂; and two remain transfusion-dependent at last follow-up at ages 5 and 30 y.o. One of the transfusion-dependent patients underwent splenectomy at 11 y.o due to misdiagnosis and returned to medical attention at 27 y.o with severe hemolytic anemia and pulmonary hypertension. All patients developed iron overload even without transfusions; four were treated with chelation. Genetic testing allowed for more rapid and accurate diagnosis; the median age of confirmed diagnosis in our cohort was 3 y.o compared to 17.3 y.o historically. In conclusion, CDAR provides an organized research network for multidisciplinary clinical and research collaboration to conduct natural history and biologic studies in CDA.

How I approach hereditary hemolytic anemia and splenectomy

Hereditary hemolytic anemias (HHA) are a heterogeneous group of anemias associated with decreased red cell survival. While there can be clinical benefit of splenectomy in many cases, splenectomy is not appropriate for all types of HHA. Additionally, there are significant risks during and following splenectomy including surgical risks, postsplenectomy sepsis, and thrombotic complications. This review discusses the diagnostic approach to HHA as well as the role of splenectomy in the management. Surgical approaches and outcomes for total and partial splenectomy are discussed.

Recommendations for Pregnancy in Rare Inherited Anemias

Rare inherited anemias are a subset of anemias caused by a genetic defect along one of the several stages of erythropoiesis or in different cellular components that affect red blood cell integrity, and thus its lifespan. Due to their low prevalence, several complications on growth and development, and multi-organ system damage are not yet well defined. Moreover, during the last decade there has been a lack of proper understanding of the impact of rare anemias on maternal and fetal outcomes. In addition, there are no clear-cut guidelines outlining the pathophysiological trends and management options unique to this special population. Here, we present on behalf of the European Hematology Association, evidence- and consensus-based guidelines, established by an international group of experts in different fields, including hematologists, gynecologists, general practitioners, medical geneticists, and experts in rare inherited anemias from various European countries for standardized and appropriate choice of therapeutic interventions for the management of pregnancy in rare inherited anemias, including Diamond-Blackfan Anemia, Congenital Dyserythropoietic Anemias, Thalassemia, Sickle Cell Disease, Enzyme deficiency and Red cell membrane disorders.

Exome sequencing for diagnosis of congenital hemolytic anemia

Background

Congenital hemolytic anemia constitutes a heterogeneous group of rare genetic disorders of red blood cells. Diagnosis is based on clinical data, family history and phenotypic testing, genetic analyses being usually performed as a late step. In this study, we explored 40 patients with congenital hemolytic anemia by whole exome sequencing: 20 patients with hereditary spherocytosis and 20 patients with unexplained hemolysis.

Results

A probable genetic cause of disease was identified in 82.5% of the patients (33/40): 100% of those with suspected hereditary spherocytosis (20/20) and 65% of those with unexplained hemolysis (13/20). We found that several patients carried genetic variations in more than one gene (3/20 in the hereditary spherocytosis group, 6/13 fully elucidated patients in the unexplained hemolysis group), giving a more accurate picture of the genetic complexity of congenital hemolytic anemia. In addition, whole exome sequencing allowed us to identify genetic variants in non-congenital hemolytic anemia genes that explained part of the phenotype in 3 patients.

Conclusion

The rapid development of next generation sequencing has rendered the genetic study of these diseases much easier and cheaper. Whole exome sequencing in congenital hemolytic anemia could provide a more precise and quicker diagnosis, improve patients’ healthcare and probably has to be democratized notably for complex cases.

Congenital Hemolytic Anemias: Is There a Role for the Immune System?

Congenital hemolytic anemias (CHAs) are a heterogeneous group of rare hereditary conditions including defects of erythrocyte membrane proteins, red cell enzymes, and disorders due to defective erythropoiesis. They are characterized by variable degree of anemia, chronic extravascular hemolysis, reduced erythrocyte life span, splenomegaly, jaundice, biliary lithiasis, and iron overload. Although few data are reported on the role of the immune system in CHAs, several immune-mediated mechanisms may be involved in the pathogenesis of these rare diseases. We reported in ~60% of patients with hereditary spherocytosis (HS), the presence of naturally-occurring autoantibodies (NAbs) directed against different membrane proteins (α- and β-spectrin, band 3, and dematin). Positive HS subjects showed a more hemolytic pattern and NAbs were more evident in aged erythrocytes. The latter is in line with the function of NAbs in the opsonization of damaged/senescent erythrocytes and their consequent removal in the spleen. Splenectomy, usually performed to reduce erythrocyte catheresis and improve Hb levels, has different efficacy in various CHAs. Median Hb increase is 3 g/dL in HS, 1.6–1.8 g/dL in pyruvate kinase deficiency (PKD), and 1 g/dL in congenital dyserythropoietic anemias (CDA) type II. Consistently with clinical severity, splenectomy is performed in 20% of HS, 45% of CDAII, and in 60% of PKD patients. Importantly, sepsis and thrombotic events have been registered, particularly in PKD with a frequency of ~7% for both. Furthermore, we analyzed the role of pro-inflammatory cytokines and found that interleukin 10 and interferon γ, and to a lesser extent interleukin 6, were increased in all CHAs compared with controls. Moreover, CDAII and enzymatic defects showed increased tumor necrosis factor-α and reduced interleukin 17. Finally, we reported that iron overload occurred in 31% of patients with membrane defects, in ~60% of CDAII cases, and in up to 82% of PKD patients (defined by MRI liver iron concentration >4 mg Fe/gdw). Hepcidin was slightly increased in CHAs compared with controls and positively correlated with ferritin and with the inflammatory cytokines interleukin 6 and interferon γ. Overall the results suggest the existence of a vicious circle between chronic hemolysis, inflammatory response, bone marrow dyserythropoiesis, and iron overload.

A complex comprising C15ORF41 and Codanin-1: the products of two genes mutated in congenital dyserythropoietic anaemia type I (CDA-I)

Congenital dyserythropoietic anaemia (CDA) type I is a rare blood disorder characterised by moderate to severe macrocytic anaemia and hepatomegaly, with spongy heterochromatin and inter-nuclear bridges seen in bone marrow erythroblasts. The vast majority of cases of CDA type I are caused by mutations in the CDAN1 gene. The product of CDAN1 is Codanin-1, which interacts the histone chaperone ASF1 in the cytoplasm. Codanin-1 is a negative regulator of chromatin replication, sequestering ASF1 in the cytoplasm, restraining histone deposition and thereby limiting DNA replication. The remainder of CDA-I cases are caused by mutations in the C15ORF41 gene, but very little is known about the product of this gene. Here, we report that C15ORF41 forms a tight, near-stoichiometric complex with Codanin1 in human cells, interacting with the C-terminal region of Codanin-1. We present the characterisation of the C15ORF41-Codanin-1 complex in humans in cells and in vitro, and demonstrate that Codanin-1 appears to sequester C15ORF41 in the cytoplasm as previously shown for ASF1. The findings in this study have major implications for understanding the functions of C15ORF41 and Codanin-1, and the aetiology of CDA-I.

Congenital dyserythropoiesis anemia type Ia with a novel CDAN1 mutation diagnosed by whole exome sequencing

Background

Congenital dyserythropoiesis anemia type Ia (OMIM:224120), is a rare hereditary anemia. The diagnosis is difficult to make and usually delayed in part due to its rarity and nonspecific clinical manifestations.

Methods

Whole exome sequencing was applied for the genetic diagnosis of a 12‐year‐old boy who has suffered from hemolytic anemia since birth and who requires regular transfusions. Sanger sequencing of the variants detected in whole exome sequencing was performed in the patient and his parents.

Results

Compound heterozygous mutations of CDAN1 gene, including one previously reported and one novel mutation, which is a splicing change, were detected in the whole exome sequencing and confirmed by Sanger sequencing. The autosomal recessive inheritance was confirmed by pedigree analysis.

Conclusion

To our knowledge, this is the first case report of congenital dyserythropoiesis anemia type Ia with genetic diagnosis to be located in Taiwan. Because of the rarity of CDA Ia and the overlapping of the clinical manifestations with other hereditary anemias, the next‐generation sequencing approach is effective for conclusive diagnosis of CDA Ia.

The BMP-SMAD pathway mediates the impaired hepatic iron metabolism associated with the ERFE-A260S variant

The erythroferrone (ERFE) is the erythroid regulator of hepatic iron metabolism by suppressing the expression of hepcidin. Congenital dyserythropoietic anemia type II (CDAII) is an inherited hyporegenerative anemia due to biallelic mutations in the SEC23B gene. Patients with CDAII exhibit marked clinical variability, even among individuals sharing the same pathogenic variants. The ERFE expression in CDAII is increased and related to abnormal erythropoiesis. We identified a recurrent low-frequency variant, A260S, in the ERFE gene in 12.5% of CDAII patients with a severe phenotype. We demonstrated that the ERFE-A260S variant leads to increased levels of ERFE, with subsequently marked impairment of iron regulation pathways at the hepatic level. Functional characterization of ERFE-A260S in the hepatic cell system demonstrated its modifier role in iron overload by impairing the BMP/SMAD pathway. We herein described for the first time an ERFE polymorphism as a genetic modifier variant. This was with a mild effect on disease expression, under a multifactorial-like model, in a condition of iron-loading anemia due to ineffective erythropoiesis.

CoDysAn: A Telemedicine Tool to Improve Awareness and Diagnosis for Patients With Congenital Dyserythropoietic Anemia

Congenital Dyserythropoietic Anemia (CDA) is a heterogeneous group of hematological disorders characterized by chronic hyporegenerative anemia and distinct morphological abnormalities of erythroid precursors in the bone marrow. In many cases, a final diagnosis is not achieved due to different levels of awareness for the diagnosis of CDAs and lack of use of advanced diagnostic procedures. Researchers have identified five major types of CDA: types I, II, III, IV, and X-linked dyserythropoietic anemia and thrombocytopenia (XLDAT). Proper management in CDA is still unsatisfactory, as the different subtypes of CDA have different genetic causes and different but overlapping patterns of signs and symptoms. For this reason, we developed a new telemedicine tool that will help doctors to achieve a faster diagnostic for this disease. Using open access code, we have created a responsive webpage named CoDysAn (Congenital Dyserythropoietic Anemia) that includes practical information for CDA awareness and a step-by-step diagnostic tool based on a CDA algorithm. The site is currently available in four languages (Catalan, Spanish, Italian, and English). This telemedicine webpage is available at http://www.codysan.eu.

Managing the Unusual Causes of Fetal Anemia

BACKGROUND

Rare causes of fetal anemia requiring intrauterine transfusion (IUT) are challenging for fetal medicine specialists.

OBJECTIVES

The aim of this study was to describe the perinatal patterns and prognosis in a consecutive series of fetuses transfused for fetal anemia of rare or unknown etiology, and to propose a protocol of investigation for fetal anemia of undetermined cause and for the management of subsequent pregnancies.

METHOD

We conducted a retrospective descriptive study on fetuses transfused for severe anemia of rare or unknown etiology managed in our national referral center (Centre National de Référence d'Hémobiologie Périnatale) and born between 2010 and 2017.

RESULTS

During the study period, 584 IUT were performed in 253 fetuses. Among those IUT, 23 (3.9%) were performed for a rare or unknown cause of anemia in 13 fetuses (5.1% of transfused fetuses). The median gestational age at diagnosis was 26 weeks of gestation (WG; range 21-33). Hemoglobin levels ranged from 1.6 to 9.1 g/dL (0.18-0.83 multiples of median) before the first IUT. The fetuses received between 1 and 6 IUT (39% received at least 2 IUT). The definitive etiologies for central anemia were: congenital syphilis, neonatal poikilocytosis, type II congenital dyserythropoietic anemia (CDA), and neonatal hemochromatosis. There was 1 case with suspected type I CDA and 1 with suspected Diamond-Blackfan anemia. There was 1 case of peripheral anemia, secondary to cerebral hemorrhages of different ages, related to a variant of the COL4A1 gene. In 6 fetuses corresponding to 4 mothers, no precise diagnosis was found despite a complete workup. In our series, there were 8 live births, 4 terminations of pregnancy, and 1 intrauterine fetal death.

CONCLUSIONS

Fetal anemia of rare or unknown diagnosis represents 5% of all transfused fetuses in our cohort. Fetal and neonatal anemias can be recurrent in further pregnancies, with variable expressivity.

The pathogenesis, diagnosis and management of congenital dyserythropoietic anaemia type I

Congenital dyserythropoietic anaemia type I (CDA-I) is one of a heterogeneous group of inherited anaemias characterised by ineffective erythropoiesis. CDA-I is caused by bi-allelic mutations in either CDAN1 or C15orf41 and, to date, 56 causative mutations have been documented. The diagnostic pathway is reviewed and the utility of genetic testing in reducing the time taken to reach an accurate molecular diagnosis and avoiding bone marrow aspiration, where possible, is described. The management of CDA-I patients is discussed, highlighting both general and specific measures which impact on disease progression. The use of interferon alpha and careful management of iron overload are reviewed and suggest the most favourable outcomes are achieved when CDA-I patients are managed with a holistic and multidisciplinary approach. Finally, the current understanding of the molecular and cellular pathogenesis of CDA-I is presented, highlighting critical questions likely to lead to improved therapy for this disease.

Rare Hereditary Hemolytic Anemias: Diagnostic Approach and Considerations in Management

Hereditary hemolytic anemias (HHAs) comprise a heterogeneous group of anemias caused by mutations in genes coding the globins, red blood cell (RBC) membrane proteins, and RBC enzymes. Congenital dyserythropoietic anemias (CDAs) are rare disorders of erythropoiesis characterized by binucleated and multinucleated erythroblasts in bone marrow. CDAs typically present with a hemolytic phenotype, as the produced RBCs have structural defects and decreased survival and should be considered in the differential of HHAs. This article discusses the clinical presentation, laboratory findings, and management considerations for rare HHAs arising from unstable hemoglobins, RBC hydration defects, the less common RBC enzymopathies, and CDAs.

Genetic disarray follows mutant KLF1-E325K expression in a congenital dyserythropoietic anemia patient

Congenital dyserythropoietic anemia type IV is caused by a heterozygous mutation, Glu325Lys (E325K), in the KLF1 transcription factor. Molecular characteristics of this disease have not been clarified, partly due to its rarity. We expanded erythroid cells from a patient's peripheral blood and analyzed its global expression pattern. We find that a large number of erythroid pathways are disrupted, particularly those related to membrane transport, globin regulation, and iron utilization. The altered genetics lead to significant deficits in differentiation. Glu325 is within the KLF1 zinc finger domain at an amino acid critical for site specific DNA binding. The change to Lys is predicted to significantly alter the target site recognition sequence, both by subverting normal recognition and by enabling interaction with novel sites. Consistent with this, we find high level ectopic expression of genes not normally present in the red cell. These altered properties explain patients' clinical and phenotypic features, and elucidate the dominant character of the mutation.

Fetal-onset Congenital Dyserythropoietic Anemia Type 1 due to a Novel Mutation With Severe Iron Overload and Severe Cholestatic Liver Disease

We report a rare case of severe congenital dyserythropoietic anemia type 1 with fetal onset. Our patient presented with fetal hydrops from 19 weeks of gestation, requiring multiple intrauterine transfusions. At birth, she had severe hemolytic anemia with severe jaundice, and was subsequently transfusion dependent. She eventually developed severe iron overload and fulminant liver failure before her demise at 5 months of age. Genetic testing revealed a novel mutation in CDAN1.

Identification of a Novel Mutation in the SEC23B Gene Associated With Congenital Dyserythropoietic Anemia Type II Through the Use of Next-generation Sequencing Panel in an Undiagnosed Case of Nonimmune Hereditary Hemolytic Anemia

Congenital dyserythropoietic anemias (CDAs) are rare hereditary blood disorders characterized by ineffective erythropoiesis, hemolysis, and erythroblast morphologic abnormalities in the bone marrow. The 3 main types of CDA, I to III, and variant types of CDA, IV-VIII, have been described. The causative genes have been identified as CDAN1, C15ORF41, SEC23B, KIF23, KLF1, and GATA1. CDA type II is the most frequent form. Typical symptoms are jaundice, hepatosplenomegaly, mild-to-severe normocytic anemia, and inadequate reticulocyte response. We report an 18-year-old boy who had chronic mild congenital anemia, jaundice, and splenomegaly mimicking nonautoimmune hemolytic anemia since 18 months of age. Compound heterozygous mutations in SEC23B gene were detected by the use of a gene-targeted next-generation sequencing panel: the already reported missense mutation c.40C>T (p.Arg14Trp), and a new frameshift deletion (c.489_489delG, p.Val164Trpfs*3), confirming the diagnosis of CDA type II. The study underlines the molecular heterogeneity of CDA II and the importance of a precise diagnosis in rare congenital diseases such as CDA II. In consequence, it can be difficult to diagnose because of limited resources, financial constraint, and rarity of disease in the developing country. Advanced laboratories and new molecular approaches may help in diagnosing rare anemias.

Clinical and genetic features of congenital dyserythropoietic anemia (CDA)

INTRODUCTION

Congenital dyserythropoietic anemias (CDA) are characterized by hyporegenerative anemia with inadequate reticulocyte values, ineffective erythropoiesis, and hemolysis. Distinctive morphology of bone marrow erythroblasts and identification of causative genes allow classification into 4 types caused by variants in CDAN1, c15orf41, SEC23B, KIF23, and KLF1 genes.

OBJECTIVE

Identify pathogenic variants in CDA patients.

METHODS

Massive parallel sequencing with a targeted gene panel, Sanger sequencing, Comparative Genome Hybridization (CGH), and in silico predictive analysis of pathogenicity.

RESULTS

Pathogenic variants were found in 21 of 53 patients studied from 44 unrelated families. Six variants were found in CDAN1: two reported, p.Arg714Trp and p.Arg725Trp and, four novel, p.Arg623Trp, p.Arg946Trp, p.Phe1125Ser and p.Ser1227Gly. Twelve variants were found in SEC23B: seven reported, p.Arg14Trp, p.Glu109Lys, p.Arg217Ter, c.835-2A>G, p.Arg535Ter, p.Arg550Ter and p.Arg718Ter and, five novel, p.Val164Leu, p.Arg190Gln, p.Gln521Ter, p.Arg546Trp, and p.Arg611Gln. The variant p.Glu325Lys in KLF1 was found in one patient and p.Tyr365Cys in ALAS2 in an other. Moreover, we identified genomic rearrangements by CGH in some SEC23B-monoallelic patients.

CONCLUSIONS

New technologies for genetic studies will help to find variants in other genes, in addition to those known, that contribute to or modulate the CDA phenotype or support the correct diagnosis.

Whole-exome analysis to detect congenital hemolytic anemia mimicking congenital dyserythropoietic anemia

Congenital dyserythropoietic anemia (CDA) is a heterogeneous group of rare congenital disorders characterized by ineffective erythropoiesis and dysplastic changes in erythroblasts. Diagnosis of CDA is based primarily on the morphology of bone marrow erythroblasts; however, genetic tests have recently become more important. Here, we performed genetic analysis of 10 Japanese patients who had been diagnosed with CDA based on laboratory findings and morphological characteristics. We examined 10 CDA patients via central review of bone marrow morphology and genetic analysis for congenital bone marrow failure syndromes. Sanger sequencing for CDAN1, SEC23B, and KLF1 was performed for all patients. We performed whole-exome sequencing in patients without mutation in these genes. Three patients carried pathogenic CDAN1 mutations, whereas no SEC23B mutations were identified in our cohort. WES unexpectedly identified gene mutations known to cause congenital hemolytic anemia in two patients: canonical G6PD p.Val394Leu mutation and SPTA1 p.Arg28His mutation. Comprehensive genetic analysis is warranted for more effective diagnosis of patients with suspected CDA.

A novel anemia associated with membranous cytoplasm degeneration in 16 patients: an ultrastructural study

Sixteen patients with mild anemia and hemolysis were difficult to be classified into any known category based on laboratory examinations and light microscopy. To make a definite diagnosis and investigate the pathomechanism, ultrastructural study was performed on erythroid cells from 16 patients. Transmission electron microscopy demonstrated a series of alterations of cytoplasm, including cytoplasm sequestration, membranous transformation, and degeneration in erythroblasts and reticulocytes at different stages. The affected erythroblasts were usually complicated with chromatin condensation, karyorrhexis, nuclear membrane lysis, and megaloblastic changes. The reticulocytes with the cytoplasm alterations had a huge size from 10 um to 15 um in diameter. The membranous cytoplasm degeneration revealed a unique pathomechanism of dyserythropoiesis and ineffective erythropoiesis in 16 patients with anemia, and suggested a novel anemia category though more details remained to be investigated.

Survey and evaluation of mutations in the human KLF1 transcription unit

Erythroid Krüppel-like Factor (EKLF/KLF1) is an erythroid-enriched transcription factor that plays a global role in all aspects of erythropoiesis, including cell cycle control and differentiation. We queried whether its mutation might play a role in red cell malignancies by genomic sequencing of the KLF1 transcription unit in cell lines, erythroid neoplasms, dysplastic disorders, and leukemia. In addition, we queried published databases from a number of varied sources. In all cases we only found changes in commonly notated SNPs. Our results suggest that if there are mutations in KLF1 associated with erythroid malignancies, they are exceedingly rare.

Identification of CDAN1, C15ORF41 and SEC23B mutations in Chinese patients affected by congenital dyserythropoietic anemia

Congenital dyserythropoietic anaemias (CDAs) are a group of rare haematological disorders characterized by ineffective erythropoiesis and dyserythropoiesis and reduced numbers of red cells, often with an abnormal morphology. Pathogenic defects in CDAN1, C15ORF41, SEC23B, KIF23, KLF1 and GATA1 genes have been identified in CDAs patients. In this study, we described 13 unrelated Chinese CDAs patients and identified 21 mutations, including 5 novel mutations in CDAN1 gene, and 5 novel mutations in SEC23B gene. Additionally, we predicted the molecular consequence of these missense mutations with Polymorphism Phenotyping v2 (Polyphen), Sorting Intolerant From Tolerant (SIFT), MutPred (http://mutpred1.mutdb.org/) and Protein Variation Effect Analyzer (Provean, http://provean.jcvi.org/seq_submit.php) and analyzed the conservation of the mutated amino acid among proteins from several mammalian species.

Neomorphic effects of the neonatal anemia (Nan-Eklf) mutation contribute to deficits throughout development

Transcription factor control of cell-specific downstream targets can be significantly altered when the controlling factor is mutated. We show that the semi-dominant neonatal anemia (Nan) mutation in the EKLF/KLF1 transcription factor leads to ectopic expression of proteins that are not normally expressed in the red blood cell, leading to systemic effects that exacerbate the intrinsic anemia in the adult and alter correct development in the early embryo. Even when expressed as a heterozygote, the Nan-EKLF protein accomplishes this by direct binding and aberrant activation of genes encoding secreted factors that exert a negative effect on erythropoiesis and iron use. Our data form the basis for a novel mechanism of physiological deficiency that is relevant to human dyserythropoietic anemia and likely other disease states.

A case of congenital dyserythropoietic anemia type IV

Congenital dyserythropoietic anemias (CDAs) are displayed by ineffective erythropoiesis. The wide variety of phenotypes observed in CDA patients makes differential diagnosis difficult; identification of the genetic variants is crucial in clinical management. We report the fifth case of a patient with unclassified CDAs, after genetic study, with CDA type IV.

Detection of new pathogenic mutations in patients with congenital haemolytic anaemia using next-generation sequencing

INTRODUCTION

Congenital haemolytic anaemia (CHA) refers to a group of genetically heterogeneous disorders, mainly caused by changes in genes encoding globin chains, cytoskeletal proteins and red cell enzymes, in which accurate diagnosis can be challenging with conventional techniques.

METHODS

To set-up a comprehensive assay for detecting mutations that could improve aetiological diagnosis, we designed a custom panel for sequencing coding regions from 40 genes known to be involved in the pathogenesis of CHA, using the Ion Torrent^™ (Thermo Fisher Scientific, S.L. Waltham, MA, USA) Personal Genome Machine (PGM) Sequencer. A control group of 16 samples with previously known mutations and a test group of 10 patients with unknown mutations were included for assay validation and application, respectively.

RESULTS

In the test group, we identified pathogenic mutations in all cases: four patients had novel mutations in genes related to membrane defects (SPTB, ANK1, SLC4A1 and EPB41), four were homozygous or compound heterozygous for mutations in genes related to enzyme deficiencies (GPI, TPI1 and GSS), one had a mutation in the HBB gene and another presented a homozygous mutation in the ADAMTS13 gene.

CONCLUSIONS

Ion PGM sequencing with our custom panel is a highly efficient way to detect mutations causing haemolytic anaemia, including new variations. It is a high-throughput detection method that is ready for application in clinical laboratories.

New Codanin-1 Gene Mutations in a Italian Patient with Congenital Dyserythropoietic Anemia Type I and Heterozygous Beta-Thalassemia

Congenital dyserythropoietic anemia type I is an autosomal recessive disorder associated with macrocytic anemia, ineffective erythropoiesis, iron overloading and characterized by abnormal chromatin ultrastructure in erythroblasts such as internuclear chromatin bridges, spongy heterochromatin and invagination of the nuclear membrane. A 58-year-old Causasian man with chronic hemolytic anemia, heterozygous for β (+) -globin IVS1, nt110 G>A mutation (causing abnormal alpha:beta globin chain ratio) showed clinical, laboratory and hematological features suggesting diagnosis of CDA1. Sequence analysis of CDA-related genes revealed compound heterozygosity for two novel mutations in the CDAN1 gene: a frameshift mutation 3367 del 4 (TTAG) in exon 25 and a missense mutation c.1811 G>T in exon 11 causing an aminoacid change from glycine to valine at codon 565 (G565V). One of the propositus' brothers showed the same gene mutations. As the CDA1 can mimic thalassemia, a frequent misdiagnosis is possible especially in countries where the prevalence of thalassemia is high. A strong clinical suspicion in patients who do not reveal a clear genetic basis for presumed thalassemia may help clinch the correct diagnosis.

Diagnosis and management of congenital dyserythropoietic anemias

Congenital dyserythropoietic anemias (CDAs) are inherited disorders hallmarked by chronic hyporegenerative anemia, relative reticulocytopenia, hemolytic component and iron overload. They represent a subtype of the inherited bone marrow failure syndromes, characterized by impaired differentiation and proliferation of the erythroid lineage. Three classical types were defined by marrow morphology, even if the most recent classification recognized six different genetic types. The pathomechanisms of CDAs are different, but all seem to involve the regulation of DNA replication and cell division. CDAs are often misdiagnosed, since either morphological abnormalities or clinical features can be commonly identified in other clinically-related anemias. However, differential diagnosis is essential for guiding both follow up and management of the patients.

Protease inhibitors-based therapy induces acquired spherocytic-like anaemia and ineffective erythropoiesis in chronic hepatitis C virus patients

BACKGROUND & AIMS

The addition of protease inhibitors, boceprevir (BOC) or telaprevir (TRV), to peg-interferon and ribavirin (PR) increases the incidence of anaemia in patients with chronic hepatitis C virus (HCV) infection. Although genetic variants in inosine triphosphatase (ITPA) gene have been linked to the haemolytic anaemia induced by PR, the mechanism sustaining severe anaemia during triple therapy is still unknown. This study aims to elucidate the molecular mechanisms underlying anaemia in chronic HCV patients with combined therapy.

METHODS

We studied 59 patients with chronic HCV genotype-1: 29 treated with TRV/PR and 30 with BOC/PR. We evaluated biochemical and haematological parameters, red cell index at baseline, 4, 12, 16 and 24 weeks of treatment; in a subgroup, we performed functional studies: osmotic fragility, red cell membrane protein separation, mass spectrometry analysis, quantification of erythroid microparticles release. IL28B and ITPA polymorphisms were also evaluated.

RESULTS

We found early acute normochromic normocytic haemolytic anaemia (4-8 weeks) followed by a late macrocytic hypo-regenerative anaemia with inappropriate low reticulocyte count (12-24 weeks). Studies on red cells revealed: (i) presence of spherocytes; (ii) increased osmotic fragility; (iii) abnormalities in red cell membrane protein composition; (iv) reduced membrane-cytoskeleton stability; (v) increased release of erythroid microparticles. ITPA polymorphisms impacted only the early phase of anaemia.

CONCLUSIONS

The bimodal pattern of anaemia in chronic HCV patients on triple therapy might be because of acquired spherocytic-like anaemia in the early phase, followed by hyporegenerative anaemia, most likely related to the combined effects of PR and TRV or BOC on erythropoiesis.

Modulation of hepcidin to treat iron deregulation: potential clinical applications

The secreted peptide hormone hepcidin regulates systemic and local iron homeostasis through degradation of the iron exporter ferroportin. Dysregulation of hepcidin leads to altered iron homeostasis and development of pathological disorders including hemochromatosis, and iron loading and iron restrictive anemias. Therapeutic modulation of hepcidin is a promising method to ameliorate these conditions. Several approaches have been taken to enhance or reduce the effects of hepcidin in vitro and in vivo. Based on these approaches, hepcidin modulating drugs have been developed and are undergoing clinical evaluation. In this article we review the rationale for development of these drugs, the data concerning their safety and efficacy, their therapeutic uses, and potential future prospects.

Acute Liver Failure in a Pediatric Patient with Congenital Dysery-Thropoietic Anemia Type I Treated with Deferasirox

Congenital dyserythropoietic anemias (CDA) represent a heterogeneous group of disorders characterized by morphological abnormalities of erythroid precursor cells and various degrees of hemolysis. Iron overload is a result of continuous hemolysis and recurrent transfusions. It is treated with iron chelators, including deferasirox. We present here a case of acute liver failure in a 12 years old girl with CDA type I treated with deferasirox and discuss the approach to treatment.

Successful Allogeneic Hematopoietic Stem Cell Transplantation of a Patient Suffering from Type II Congenital Dyserythropoietic Anemia A Rare Case Report from Western India

The most frequent form of congenital dyserythropoiesis (CDA) is congenital dyserythropoietic anemia II (CDA II). CDA II is a rare genetic anemia in humans, inherited in an autosomally recessive mode, characterized by hepatosplenomegaly normocytic anemia and hemolytic jaundice. Patients are usually transfusion-independent except in severe type. We are here reporting a case of severe transfusion-dependent type II congenital dyserythropoietic anemia in a 5-year-old patient who has undergone allogeneic hematopoietic stem cell transplantation (HSCT) at our bone marrow transplantation centre. Patient has had up until now more than 14 mL/kg/month of packed cell volume (PCV), which he required every 15 to 20 days to maintain his hemoglobin of 10 gm/dL and hematocrit of 30%. His pre-HSCT serum ferritin was 1500 ng/mL and he was on iron chelating therapy. Donor was HLA identical sibling (younger brother). The preparative regimen used was busulfan, cyclophosphamide, and antithymocyte globulin (Thymoglobulin). Cyclosporine and short-term methotrexate were used for graft versus host disease (GVHD) prophylaxis. Engraftment of donor cells was quick and the posttransplant course was uneventful. The patient is presently alive and doing well and he has been transfusion-independent for the past 33 months after HSCT.

Compound heterozygosity for KLF1 mutations is associated with microcytic hypochromic anemia and increased fetal hemoglobin

Krüppel-like factor 1 (KLF1) regulates erythroid lineage commitment, globin switching, and the terminal maturation of red blood cells. Variants in human KLF1 have been identified as an important causative factor in a wide spectrum of phenotypes. This study investigated two unrelated male children in China who had refractory anemia associated with poikilocythemia. These were accompanied by an upregulation of biochemical markers of hemolysis, along with abnormal hemoglobin (Hb) level and elevated reticulocyte counts. Next-generation sequencing revealed that the patients were compound heterozygotes for a KLF1 frameshift mutation c.525_526insCGGCGCC (p.(Gly176ArgfsTer179)) and one of two missense variants, c.892 G>C (p.(Ala298Pro)) and c.1012C>T (p.(Pro338Ser)). The subjects had microcytic hypochromic anemia, and their healthy parents had single mutation. The two missense mutations affected a highly conserved codon in the zinc finger DNA-binding domain of KLF1, but the protein stability was unaffected in K-562 cells. A KLF1-targeted promoter-reporter assay showed that the two mutations reduce the expression of the HBB, BCL11A, and CD44 genes involved in erythropoiesis, with consequent dyserythropoiesis and an α/non-α chain imbalance. A systematic analysis was performed of the phenotypes associated with the KLF1 mutations in the two families, and the clinical characteristics and differential diagnoses of the disease are presented. This is the first report of an autosomal recessive anemia presenting with microcytic hypochromia, abnormal Hb profile, and other distinctive erythrocyte phenotypes, and provides insight into the multiple roles of KLF1 during erythropoiesis.