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

Cytoskeletal Protein 4.1R in Health and Diseases

The protein 4.1R is an essential component of the erythrocyte membrane skeleton, serving as a key structural element and contributing to the regulation of the membrane's physical properties, including mechanical stability and deformability, through its interaction with spectrin-actin. Recent research has uncovered additional roles of 4.1R beyond its function as a linker between the plasma membrane and the membrane skeleton. It has been found to play a crucial role in various biological processes, such as cell fate determination, cell cycle regulation, cell proliferation, and cell motility. Additionally, 4.1R has been implicated in cancer, with numerous studies demonstrating its potential as a diagnostic and prognostic biomarker for tumors. In this review, we provide an updated overview of the gene and protein structure of 4.1R, as well as its cellular functions in both physiological and pathological contexts.

Targeted next-generation sequencing identifies novel deleterious variants in ANK1 gene causing severe hereditary spherocytosis in Indian patients: expanding the molecular and clinical spectrum

Hereditary Spherocytosis (HS) is a common cause of hemolytic anemia varying from mild to severe hemolysis due to defects in red cell membrane protein genes, namely ANK1, SPTB, SPTA1, SLC4A1, and EPB42. These genes are considerably very large spaning 40-50 exons making gene-by-gene analysis costly and laborious by conventional methods. In this study, we explored 26 HS patients harboring 21 ANK1 variants identified by next-generation sequencing (NGS), characteristics and spectrum of the detected ANK1variants were analyzed in this study. Clinically, all the HS patients showed moderate to severe transfusion-dependent hemolytic anemia, some requiring splenectomy. We identified 13 novel and 8 reported variants, mainly 9 frameshifts, 2 missense, 6 nonsense, and 4 splice site ANK1 variants, using NGS technology. Frameshifts were remarkably the most common variant type seen in Indian HS patients with ANK1 gene defects. We have also explored expression levels of red cell membrane ankyrin protein by flow cytometry in 14 HS patients with ANK1 gene defects and a significant reduction in ankyrin protein expression has been found. This report mainly illustrates the molecular and phenotypic heterogeneity of ANK1 variants causing HS in Indian patients. Ankyrin-1 mutations are a significant cause of loss of function in dominant HS in the Indian population. Comprehensive genetic and phenotypic evaluation assists in implementing the knowledge of genetic patterns and spectrum of ANK1 gene variants, providing molecular support for HS diagnosis.

Unravelling the genetic and phenotypic heterogeneity of SPTA1 gene variants in Hereditary Elliptocytosis and Hereditary Pyropoikilocytosis patients using next-generation sequencing

Hereditary Elliptocytosis (HE) and Hereditary Pyropoikilocytosis (HPP) are clinically and genetically heterogeneous red cell membranopathies that result from the defects in the horizontal linkage between RBC (red blood cell) membrane and cytoskeletal proteins affecting its mechanical stability and deformability thereby reducing its lifespan. The principal defect in HE and HPP is due to dysfunction or deficiency of RBC cytoskeletal proteins namely, α-spectrin (SPTA1), β-spectrin (SPTB) and protein 4.1R (EPB41R). This study reports the genetic and phenotypic heterogeneity of 10 Indian patients (5 with HE and 5 with HPP)harboringSPTA1 gene variants. We used targeted next-generation sequencing (t-NGS) to characterize the causative genetic variants in 10 HE/HPP suspected patients and studied the correlation between the identified variants with their corresponding phenotypic features.t-NGS detected 12 SPTA1 variants, out of which 8 are novel. Nearly all of the detected variants have a damaging effect on the protein stability and function, as shown by the insilico analysis. The possible effect of the detected variants on the protein structure was studied using the HOPE software and DynaMut tools wherever possible. To the best of our knowledge, this is the first report on HE/HPP cases confirmed by a genetic study from India. To conclude, HE is caused by monoallelic mutations while HPP, the more severe form, is typically caused by biallelic (homozygous or compound heterozygous) mutations justifying the phenotypic heterogeneity associated with patients. Moreover, analysis at the molecular level by NGS permits diagnosis in these disorders with highly variable heterogeneity requiring regular transfusions and may facilitate prognostic contemplations.

Clinical and genetic diagnosis of thirteen Japanese patients with hereditary spherocytosis

Hereditary spherocytosis is the most frequent cause of hereditary hemolytic anemia and is classified into five subtypes (SPH1-5) according to OMIM. Because the clinical and laboratory features of patients with SPH1-5 are variable, it is difficult to classify these patients into the five subtypes based only on these features. We performed target capture sequencing in 51 patients with hemolytic anemia associated with/without morphological abnormalities in red blood cells. Thirteen variants were identified in five hereditary spherocytosis-related genes (six in ANK1 [SPH1]; four in SPTB [SPH2]; and one in each of SPTA1 [SPH3], SLC4A1 [SPH4], and EPB42 [SPH5]). Among these variants, seven were novel. The distribution pattern of the variants was different from that reported previously in Japan but similar to those reported in other Asian countries. Comprehensive genomic analysis would be useful and recommended, especially for patients without a detailed family history and those receiving frequent blood transfusions due to chronic hemolytic anemia.

Impact of Next-Generation Sequencing on the Diagnosis and Treatment of Congenital Anemias

Congenital anemias are a wide spectrum of diseases including hypoproliferative anemia syndromes, dyserythropoietic anemias, sideroblastic anemias, red blood cell membrane and enzymatic defects, hemoglobinopathies, and thalassemia syndromes. The various congenital anemia syndromes may have similar clinical and laboratory presentations, making the diagnosis challenging. The traditional work-up, which includes a complete blood count, blood smears, bone marrow studies, flow cytometry, and the osmotic fragility test, does not always lead to the diagnosis. Specialized tests such as red blood cell enzyme activity and ektacytometry are not widely available. In addition, red blood cell transfusions may mask some of the laboratory characteristics. Therefore, genetic testing is crucial for accurate diagnosis of patients with congenital anemias. However, gene-by-gene testing is labor intensive because of the large number of genes involved. Thus, targeted next-generation sequencing using custom-made gene panels has been increasingly utilized, with a high success rate of diagnosis. Accurate genetic diagnosis is important for determining specific therapeutic modalities, as well as for avoiding splenectomy when contraindicated. In addition, molecular diagnosis can allow for genetic counseling and prenatal diagnosis in severe cases. We suggest a work-up scheme for patients with congenital anemias, including early incorporation of targeted next-generation sequencing panels.

Targeted Next Generation Sequencing and Diagnosis of Congenital Hemolytic Anemias: A Three Years Experience Monocentric Study

Congenital hemolytic anemias (CHAs) are heterogeneous and rare disorders caused by alterations in structure, membrane transport, metabolism, or red blood cell production. The pathophysiology of these diseases, in particular the rarest, is often poorly understood, and easy-to-apply tools for diagnosis, clinical management, and patient stratification are still lacking. We report the 3-years monocentric experience with a 43 genes targeted Next Generation Sequencing (t-NGS) panel in diagnosis of CHAs; 122 patients from 105 unrelated families were investigated and the results compared with conventional laboratory pathway. Patients were divided in two groups: 1) cases diagnosed with hematologic investigations to be confirmed at molecular level, and 2) patients with unexplained anemia after extensive hematologic investigation. The overall sensitivity of t-NGS was 74 and 35% for families of groups 1 and 2, respectively. Inside this cohort of patients we identified 26 new pathogenic variants confirmed by functional evidence. The implementation of laboratory work-up with t-NGS increased the number of diagnoses in cases with unexplained anemia; cytoskeleton defects are well detected by conventional tools, deserving t-NGS to atypical cases; the diagnosis of Gardos channelopathy, some enzyme deficiencies, familial siterosterolemia, X-linked defects in females and other rare and ultra-rare diseases definitely benefits of t-NGS approaches.

Screening tools for hereditary hemolytic anemia: new concepts and strategies

INTRODUCTION

Hereditary hemolytic anemias are a group of rare and heterogeneous disorders due to abnormalities in structure, metabolism, and transport functions of erythrocytes; they may overlap in clinical and hematological features making differential diagnosis difficult, particularly in mild and atypical forms.

AREAS COVERED

In the present review, the main tools currently adopted in routine hematologic investigation for the diagnosis of hereditary hemolytic anemias are described, together with the new diagnostic approaches that are being to be developed in the next future. Available recommendations in this field together with a systematic review through MEDLINE, EMBASE, and PubMED for publications in English from 2000 to 2020 in regards to diagnostic aspects of hereditary hemolytic anemias have been considered.

EXPERT OPINION

The recent development of specific molecules and treatments for hereditary hemolytic anemias and the increased interest in translational research raised the attention on differential diagnosis and the demand for novel diagnostic assays and devices. Automatic blood cell analyzers, omic-approaches including NGS technologies, and development of new automated tools based on artificial neural networks definitely represent the future strategies in this field.

Genetics and Genomics Approaches for Diagnosis and Research Into Hereditary Anemias

The hereditary anemias are a relatively heterogeneous set of disorders that can show wide clinical and genetic heterogeneity, which often hampers correct clinical diagnosis. The classical diagnostic workflow for these conditions generally used to start with analysis of the family and personal histories, followed by biochemical and morphological evaluations, and ending with genetic testing. However, the diagnostic framework has changed more recently, and genetic testing is now a suitable approach for differential diagnosis of these patients. There are several approaches to this genetic testing, the choice of which depends on phenotyping, genetic heterogeneity, and gene size. For patients who show complete phenotyping, single-gene testing remains recommended. However, genetic analysis now includes next-generation sequencing, which is generally based on custom-designed targeting panels and whole-exome sequencing. The use of next-generation sequencing also allows the identification of new causative genes, and of polygenic conditions and genetic factors that modify disease severity of hereditary anemias. In the research field, whole-genome sequencing is useful for the identification of non-coding causative mutations, which might account for the disruption of transcriptional factor occupancy sites and cis-regulatory elements. Moreover, advances in high-throughput sequencing techniques have now resulted in the identification of genome-wide profiling of the chromatin structures known as the topologically associating domains. These represent a recurrent disease mechanism that exposes genes to inappropriate regulatory elements, causing errors in gene expression. This review focuses on the challenges of diagnosis and research into hereditary anemias, with indications of both the advantages and disadvantages. Finally, we consider the future perspectives for the use of next-generation sequencing technologies in this era of precision medicine.

Beta-Spectrin Deletion Responsible for Hereditary Spherocytosis: When New Technologies Are Not the Key to Success

Hereditary spherocytosis arises from alterations in the genes encoding red blood cell membrane proteins. Although its diagnosis is mostly clinical, recent advances in next-generation sequencing (NGS) technologies have allowed for a faster cost-effective gene-based diagnosis. We report the case of a boy with spherocytic anemia and development delay in whom a de novo 2.84-Mb deletion at chromosome 14 including SPTB (ß-spectrin gene) was identified by array-based comparative genomic hybridization. This alteration, consistent with de novo spherocytosis, was missed by a NGS gene panel. When associated with other symptoms, especially neurologic, NGS may not be appropriate to genetically diagnose spherocytic anemia.

Molecular heterogeneity of pyruvate kinase deficiency

Red cell pyruvate kinase (PK) deficiency is the most common glycolytic defect associated with congenital non-spherocytic hemolytic anemia. The disease, transmitted as an autosomal recessive trait, is caused by mutations in the PKLR gene and is characterized by molecular and clinical heterogeneity; anemia ranges from mild or fully compensated hemolysis to life-threatening forms necessitating neonatal exchange transfusions and/or subsequent regular transfusion support; complications include gallstones, pulmonary hypertension, extramedullary hematopoiesis and iron overload. Since identification of the first pathogenic variants responsible for PK deficiency in 1991, more than 300 different variants have been reported, and the study of molecular mechanisms and the existence of genotype-phenotype correlations have been investigated in-depth. In recent years, during which progress in genetic analysis, next-generation sequencing technologies and personalized medicine have opened up important landscapes for diagnosis and study of molecular mechanisms of congenital hemolytic anemias, genotyping has become a prerequisite for accessing new treatments and for evaluating disease state and progression. This review examines the extensive molecular heterogeneity of PK deficiency, focusing on the diagnostic impact of genotypes and new acquisitions on pathogenic non-canonical variants. The recent progress and the weakness in understanding the genotype-phenotype correlation, and its practical usefulness in light of new therapeutic opportunities for PK deficiency are also discussed.

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.

Next-Generation Sequencing-Based Diagnosis of Unexplained Inherited Hemolytic Anemias Reveals Wide Genetic and Phenotypic Heterogeneity

Determination of the cause of inherited hemolysis is based on clinical and stepwise conventional laboratory tests. Patients with obscure etiology require genetic diagnosis, which is time-consuming, expensive, and laborious, mainly because of numerous causal genes. This study enrolled 43 patients with clinical and laboratory evidence of unexplained hemolytic anemia. Initially, 13 patients were tested using a commercial (TruSight One) panel, and remaining cases underwent targeted sequencing using a customized 55-gene panel. Pyruvate kinase deficiency was found in eight, glucose-6-phosphate dehydrogenase (G6PD) deficiency in three (G6PD Guadalajara in two and p.Tyr227Ser: novel, named as G6PD Chandigarh), and glucose-6-phosphate isomerase (GPI) deficiency in two (GPI:p.Arg347His and p.Phe304Leu: novel, named as GPI Chandigarh). Three patients had Mediterranean stomatocytosis/macrothrombocytopenia, and two had overhydrated stomatocytosis. Xerocytosis was found in three patients, whereas six had potentially pathogenic variants in membrane protein-coding genes. Overall, 63% cases received a definite diagnosis. Timely determination of etiology was helpful in diagnosis, genetic counseling, and offering a prenatal diagnosis. Therapeutic implications include performing or avoiding splenectomy that may ameliorate the anemia in many but also predispose to thrombosis in other groups of patients. This first study on the genetic spectrum of unexplained hemolytic anemia from the Indian subcontinent also represents, currently, one of the largest cohort worldwide of such patients.

Deciphering molecular heterogeneity of Indian families with hereditary spherocytosis using targeted next-generation sequencing: First South Asian study

Defects in various erythrocyte membrane proteins genes (ankyrin, band-3, β- and α-spectrin and protein 4·2) can cause hereditary spherocytosis (HS). This molecular heterogeneity of HS, together with co-inherited genetic modifiers, results in marked phenotypic variability among patients. We studied the molecular spectrum and genotype-phenotype correlations in 73 families (with 113 patients) with HS. Deleterious variants including nonsense (42%), deletions (18%), splice site (20%), missense (10%) and duplication/insertion (10%) were found in 47 patients. The variants detected included sporadic and dominantly-inherited defects in ANK1 (53·2%), SPTB (36·2%) and SLC4A1 (4·2%). Compound heterozygous variants in SPTA1 (6·4%) showed autosomal recessive inheritance. Alpha-spectrin variants were associated with severe anaemia and splenectomy alleviated symptoms. Co-inherited glucose-6-phosphate dehydrogenase (G6PD) deficiency was found in 15%. G6PD variants (n = 5) led to greater transfusion requirements (1-8 times) in males with HS. Homozygosity (41%) for the promoter variant of UGT1A1 (Gilbert syndrome) led to a significantly higher mean bilirubin level (126·54 µmol/l) with a higher frequency of cholelithiasis (30%) (P < 0·001). This first-ever south Asian study on the molecular spectrum of HS found ANK1 and SPTB genes variants to be the commonest with inheritance being sporadic/dominant. Next-generation sequencing provided a relatively sensitive and rapid tool for molecular diagnosis with a diagnostic yield of 64·4%.

Study of pathophysiology and molecular characterization of congenital anemia in India using targeted next-generation sequencing approach

Most patients with anemia are diagnosed through clinical phenotype and basic laboratory testing. Nonetheless, in cases of rare congenital anemias, some patients remain undiagnosed despite undergoing an exhaustive workup. Genetic testing is complicated by the large number of genes that are involved in rare anemias, due to similarities in the clinical presentation. We sought to enhance the diagnosis of patients with congenital anemias by using targeted next-generation sequencing. The genetic diagnosis was performed by gene capture followed by next-generation sequencing of 76 genes known to cause anemia syndromes. Genetic diagnosis was achieved in 17 of 21 transfusion-dependent patients and undiagnosed by conventional workup. Four cases were diagnosed with red cell membrane protein defects, four patients were diagnosed with pyruvate kinase deficiency, one case of adenylate kinase deficiency, one case of glucose phosphate isomerase deficiency, one case of hereditary xerocytosis, three cases having combined membrane and enzyme defect, two cases with Diamond-Blackfan anemia (DBA) and 1 with CDA type II with 26 different mutations, of which 21 are novel. Earlier incorporation of this NGS method into the workup of patients with congenital anemia may improve patient care and enable genetic counselling.

Molecular diagnosis of hereditary spherocytosis by multi-gene target sequencing in Korea: matching with osmotic fragility test and presence of spherocyte

Background

Current diagnostic tests for hereditary spherocytosis (HS) focus on the detection of hemolysis or indirectly assessing defects of membrane protein, whereas direct methods to detect protein defects are complicated and difficult to implement. In the present study, we investigated the patterns of genetic variation associated with HS among patients clinically diagnosed with HS.

Methods

Multi-gene targeted sequencing of 43 genes (17 RBC membrane protein-encoding genes, 20 RBC enzyme-encoding genes, and six additional genes for the differential diagnosis) was performed using the Illumina HiSeq platform.

Results

Among 59 patients with HS, 50 (84.7%) had one or more significant variants in a RBC membrane protein-encoding genes. A total of 54 significant variants including 46 novel mutations were detected in six RBC membrane protein-encoding genes, with the highest number of variants found in SPTB (n = 28), and followed by ANK1 (n = 19), SLC4A1 (n = 3), SPTA1 (n = 2), EPB41 (n = 1), and EPB42 (n = 1). Concurrent mutations of genes encoding RBC enzymes (ALDOB, GAPDH, and GSR) were detected in three patients. UGT1A1 mutations were present in 24 patients (40.7%). Positive rate of osmotic fragility test was 86.8% among patients harboring HS-related gene mutations.

Conclusions

This constitutes the first large-scaled genetic study of Korean patients with HS. We demonstrated that multi-gene target sequencing is sensitive and feasible that can be used as a powerful tool for diagnosing HS. Considering the discrepancies of clinical and molecular diagnoses of HS, our findings suggest that molecular genetic analysis is required for accurate diagnosis of HS.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-1070-0) contains supplementary material, which is available to authorized users.

A de novo ANK1 mutation associated to hereditary spherocytosis: a case report

Background

Hereditary spherocytosis (HS) is a type of hemolytic anemia caused by abnormal red cell membrane skeletal proteins with few unique clinical manifestations in the neonate and infant. An ANK1 gene mutation is the most common cause of HS.

Case presentation

The patient was a 11-month-old boy who suffered from anemia and needed a regular transfusion therapy at an interval of 2–3 months. Hematological investigations showed moderate anemia (Hb80 g/L). Red cells displayed microcytosis (MCV76.4 fl, MCH25.6 pg, MCHC335 g/L). The reticulocytes were elevated (4.8%) and the spherocytes were increased (10%). Direct antiglobulin test was negative. Biochemical test indicated a slight elevation of bilirubin, mainly indirect reacting (TBIL32.5 μmol/L, IBIL24 μmol/L). The neonatal HS ratio is 4.38, obviously up the threshold. Meanwhile, a de novo ANK1 mutation (exon 25:c.2693dupC:p.A899Sfs*11) was identified by next-generation sequencing (NGS). Thus, hereditary spherocytosis was finally diagnosed.

Conclusions

Gene detection should be considered in some hemolytic anemia which is difficult to diagnose by routine means. We identified a novel de novo ANK1 heterozygous frameshift mutation in a Yi nationality patient while neither of his parents carried this mutation.

Electronic supplementary material

The online version of this article (10.1186/s12887-019-1436-4) contains supplementary material, which is available to authorized users.

Addressing the diagnostic gaps in pyruvate kinase deficiency: Consensus recommendations on the diagnosis of pyruvate kinase deficiency

Pyruvate kinase deficiency (PKD) is the most common enzyme defect of glycolysis and an important cause of hereditary, nonspherocytic hemolytic anemia. The disease has a worldwide geographical distribution but there are no verified data regarding its frequency. Difficulties in the diagnostic workflow and interpretation of PK enzyme assay likely play a role. By the creation of a global PKD International Working Group in 2016, involving 24 experts from 20 Centers of Expertise we studied the current gaps in the diagnosis of PKD in order to establish diagnostic guidelines. By means of a detailed survey and subsequent discussions, multiple aspects of the diagnosis of PKD were evaluated and discussed by members of Expert Centers from Europe, USA, and Asia directly involved in diagnosis. Broad consensus was reached among the Centers on many clinical and technical aspects of the diagnosis of PKD. The results of this study are here presented as recommendations for the diagnosis of PKD and used to prepare a diagnostic algorithm. This information might be helpful for other Centers to deliver timely and appropriate diagnosis and to increase awareness in PKD.

Whole-exome sequencing for the genetic diagnosis of congenital red blood cell membrane disorders in Taiwan

PURPOSE

Congenital hemolytic anemia caused by red blood cell (RBC) membrane defects is a heterogeneous group of disorders. The present study aimed to search the causative gene mutations in patients with RBC membrane disorders in Taiwan.

MATERIALS AND METHODS

Next-generation sequencing approach using whole-exome sequencing (WES) was performed. Sanger sequencing was performed for confirmation of variants detected in WES in patients and their family members.

RESULTS

Five causative variants, including two ANK1, two SPTA and one SPTB variants, were detected in four patients. All these variants, except one SPTA1 variant c.83G > A (p.R28H), are novel variants. Their pedigree analysis showed one de novo SPTA1 mutation c.83G > A (p.R28H) combined with α^LELY, one de novo ANK1 mutation c.1034C > A (p.A345E), one autosomal dominant combined SPTA1 c.4604A > C (p.Q1535P) and SPTB c.6203 T > C (p.L2068P) mutations and one autosomal dominant ANK1 c.4462C > T (p.R1488X) mutation.

CONCLUSIONS

Our data demonstrated that WES is an efficient tool for determining genetic etiologies of RBC membrane disorders and can facilitate accurate diagnosis and genetic counseling. Additional studies should be conducted on larger cohorts to investigate the distribution of gene mutations in patients with RBC membrane disorders in Taiwan.

Spectrum of Ankyrin Mutations in Hereditary Spherocytosis: A Case Report and Review of the Literature

BACKGROUND/AIMS

Hereditary spherocytosis (HS) is a common pediatric hemolytic anemia caused by congenital red blood cell defects. HS due to ankyrin 1 (ANK1) mutations is the most common type. We explored an ANK1 mutation from an HS patient and reviewed the literature.

METHODS

We detected the mutation in a Chinese family in which 2 members were diagnosed with HS by next-generation sequencing. The proband was diagnosed with HS in the newborn period, based on clinical manifestations, laboratory data, and family history. The mutation spectrum of the ANK1 gene was summarized based on 85 patients diagnosed with HS carrying ANK1 mutations, and the ANK1 mutation spectrum was summarized and analyzed.

RESULTS

We identified a novel mutation affecting ANK1 gene splicing (a splicing mutation) in both the patient and her mother, which is a substitution of T>G 2 nt after exon 25 in intron 26. The study expands our knowledge of the ANK1 gene mutation spectrum, providing a molecular basis for HS.

CONCLUSION

A novel ANK1 mutation (NM_000037.3, c.2960+2T>G, intron 26) that is potentially associated with HS was identified. To date, 80 ANK1 mutations have been reported to be associated with HS in humans.

Multi-gene panel testing improves diagnosis and management of patients with hereditary anemias

Mutations in more than 70 genes cause hereditary anemias (HA), a highly heterogeneous group of rare/low frequency disorders in which we included: hyporegenerative anemias, as congenital dyserythropoietic anemia (CDA) and Diamond-Blackfan anemia; hemolytic anemias due to erythrocyte membrane defects, as hereditary spherocytosis and stomatocytosis; hemolytic anemias due to enzymatic defects. The study describes the diagnostic workflow for HA, based on the development of two consecutive versions of a targeted-NGS panel, including 34 and 71 genes, respectively. Seventy-four probands from 62 unrelated families were investigated. Our study includes the most comprehensive gene set for these anemias and the largest cohort of patients described so far. We obtained an overall diagnostic yield of 64.9%. Despite 54.2% of cases showed conclusive diagnosis fitting well to the clinical suspicion, the multi-gene analysis modified the original clinical diagnosis in 45.8% of patients (nonmatched phenotype-genotype). Of note, 81.8% of nonmatched patients were clinically suspected to suffer from CDA. Particularly, 45.5% of the probands originally classified as CDA exhibited a conclusive diagnosis of chronic anemia due to enzymatic defects, mainly due to mutations in PKLR gene. Interestingly, we also identified a syndromic CDA patient with mild anemia and epilepsy, showing a homozygous mutation in CAD gene, recently associated to early infantile epileptic encephalopathy-50 and CDA-like anemia. Finally, we described a patient showing marked iron overload due to the coinheritance of PIEZO1 and SEC23B mutations, demonstrating that the multi-gene approach is valuable not only for achieving a correct and definitive diagnosis, but also for guiding treatment.

A novel PKLR gene mutation identified using advanced molecular techniques

This study's purposes were to diagnose intractable hemolytic anemia and to provide guiding treatment for the affected family members. We performed NGS in a panel of 600 genes for blood diseases on a patient with obscure hemolytic anemia and her parents. We confirmed the diagnosis of pyruvate kinase deficiency, identified a novel homozygous mutation of the PKLR gene (NM_000298: exon 6: c.T941C: p.I314T), and ruled out other blood diseases in the Chinese family. Furthermore, amniotic fluid was taken from the mother during the second trimester, and DNA was extracted to analyze the type of PKLR gene mutation. The proband received cord blood and bone marrow from the second child of the mother for hematopoietic stem cell transplantation and achieved normal hematopoiesis. The genetic characterization analysis and genotype-phenotype correlation study of PKLR gene suggested that NGS was an effective method to confirm the molecular diagnosis of intractable hemolytic anemia. The identification of the mutation aided in prenatal diagnosis in the second pregnancy and the effective clinical management of the affected family.

An ANK1 IVS3-2A>C mutation causes exon 4 skipping in two patients from a Chinese family with hereditary spherocytosis

Hereditary spherocytosis (HS) is a congenital hemolytic anemia that affects the cell membrane of red blood cells and is characterized by the presence of spherical-shaped erythrocytes in the peripheral blood film. The clinical manifestation of HS ranges from asymptomatic to severe cases that require transfusion during early childhood. HS is caused by mutations in red blood cell membrane protein encoding genes, including ANK1, EPB42, SLC4A1, SPTA1, and SPTB. Mutations of the ANK1 gene account for 75% of all HS cases, and these particular mutations are typically inherited in an autosomal dominant manner. In this study, heterozygous an ANK1 IVS3-2A>C mutation was identified in a 7-year-old girl with Coombs-negative and severe hemolytic jaundice using targeted next-generation sequencing (NGS) and Sanger sequencing. Spherocytes were observed in a peripheral smear. Osmotic fragility was increased, and glucose-6-phosphate dehydrogenase (G6PD) activity was normal. A genetic mutation screen for α- and β-thalassemia was negative. Autoimmune antibody tests were negative. Both the girl and her affected father received a splenectomy. Patient-derived peripheral blood mononuclear cells showed skipping of exon 4 in the mRNA, which confirmed the splicing mutation effect of the ANK1 IVS3-2A>C mutation. Moreover, the anemia was ameliorated after splenectomy. Our results demonstrate that the ANK1 IVS3-2A>C mutation may lead to exon 4 skipping of the ANK1 gene and cause HS.

Novel mutations in patients with hereditary red blood cell membrane disorders using next-generation sequencing

To diagnose and investigate the genotype-phenotype relationship in intractable hereditary red blood cell (RBC) membrane cases, we have utilized next-generation sequencing (NGS) to develop a high-throughput, highly sensitive assay. Three unrelated families including 15 individuals were analysed with a panel interrogating 600 genes related to haematopathy disorders. Where possible, inheritance patterns of pathogenic mutations were determined by sequencing the relatives. We identified 2 novel mutations in ANK1 (Y216X and E142X) responsible for hereditary spherocytosis (HS) that were stop-gain single nucleotide variants (SNVs). Furthermore, a novel SPTA1 mutation (H54P) was identified; it is a nonsynonymous SNV and is associated with hereditary elliptocytosis (HE). In addition, patients who also carried erythropoiesis gene mutations showed more severe disease phenotype. The NGS panel provides a fast and accurate method for molecular diagnosis in patients with intractable hereditary RBC membrane disorders. An approach integrating medical history, clinical and molecular testing, and pedigree analysis is beneficial for these patients and families.

Combined study of ADAMTS13 and complement genes in the diagnosis of thrombotic microangiopathies using next-generation sequencing

BACKGROUND

The 2 main forms of thrombotic microangiopathy (TMA) are thrombotic thrombocytopenic purpura (TTP) and atypical hemolytic uremic syndrome (aHUS). Deficiency of ADAMTS13 and dysregulation of the complement pathway result in TTP and aHUS, respectively; however, overlap of their clinical characteristics makes differential diagnosis challenging.

OBJECTIVES AND METHODS

We aimed to develop a TMA diagnosis workflow based on ADAMTS13 activity and screening of ADAMTS13 and complement genes using a custom next-generation sequencing (NGS) gene panel.

PATIENTS

For this, from a cohort of 154 Portuguese patients with acute TMA, the genotype-phenotype correlations were analyzed in 7 hereditary TTP (ADAMTS13 activity <10%, no inhibitor), 36 acquired TTP (ADAMTS13 activity <10%, presence of an inhibitor), and in 34 presumable aHUS.

RESULTS

In total, 37 different rare variants, 8 of which novel (in ADAMTS13,CFH, and CD46), were identified across 7 genes. Thirteen TTP patients were homozygous (n=6), compound heterozygous (n=2), and heterozygous (n=5) for 11 ADAMTS13 variants (6 pathogenic mutations). Among the 34 aHUS patients, 17 were heterozygous for 23 variants in the different complement genes with distinct consequences, ranging from single pathogenic mutations associated with complete disease penetrance to benign variants that cause aHUS only when combined with other variants and/or CFH and CD46 risk haplotypes or CFHR1-3 deletion.

CONCLUSIONS

Our study provides evidence of the usefulness of the NGS panel as an excellent technology that enables more rapid diagnosis of TMA, and is a valuable asset in clinical practice to discriminate between TTP and aHUS.

Diagnostic approaches for inherited hemolytic anemia in the genetic era

Inherited hemolytic anemias (IHAs) are genetic diseases that present with anemia due to the increased destruction of circulating abnormal RBCs. The RBC abnormalities are classified into the three major disorders of membranopathies, hemoglobinopathies, and enzymopathies. Traditional diagnosis of IHA has been performed via a step-wise process combining clinical and laboratory findings. Nowadays, the etiology of IHA accounts for germline mutations of the responsible genes coding for the structural components of RBCs. Recent advances in molecular technologies, including next-generation sequencing, inspire us to apply these technologies as a first-line approach for the identification of potential mutations and to determine the novel causative genes in patients with IHAs. We herein review the concept and strategy for the genetic diagnosis of IHAs and provide an overview of the preparations for clinical applications of the new molecular technologies.