Genotype-phenotype correlation and molecular heterogeneity in pyruvate kinase deficiency

Mortality among US veterans with a physician-documented diagnosis of pyruvate kinase deficiency

Real-world studies of pyruvate kinase (PK) deficiency and estimates of mortality are lacking. This retrospective observational study aimed to identify patients with PK deficiency and compare their overall survival (OS) to that of a matched cohort without PK deficiency. Patients with ≥1 diagnosis code related to PK deficiency were selected from the US Veterans Health Administration (VHA) database (01/1995-07/2019); patients with a physician-documented diagnosis were included (PK deficiency cohort; index: date of first diagnosis code related to PK deficiency). Patients in the PK deficiency cohort were matched 1:5 to patients from the general VHA population (non-PK deficiency cohort; index: random visit date during match's index year). OS from index was compared between the two cohorts. Eighteen patients in the PK deficiency cohort were matched to 90 individuals in the non-PK deficiency cohort (both cohorts: mean age 57 years, 94% males; median follow-up 6.0 and 8.0 years, respectively). At follow-up, patients in the non-PK deficiency cohort had significantly longer OS than the PK deficiency cohort (median OS: 17.1 vs. 10.9 years; hazard ratio: 2.3; p = 0.0306). During their first-year post-index, 75% and 40% of the PK deficiency cohort had laboratory-confirmed anemia and iron overload, respectively. Among patients who died, cause of death was highly heterogeneous. These results highlight the increased risk of mortality and substantial clinical burden among patients with PK deficiency. While the intrinsic characteristics of the VHA database may limit the generalizability of the results, this is the first real-world study to characterize mortality in patients with PK deficiency.

Pyruvate kinase deficiency in 29 Turkish patients with two novel intronic variants

Pyruvate kinase (PK) is a key enzyme of anaerobic glycolysis. The genetic heterogeneity of PK deficiency (PKD) is high, and over 400 unique variants have been identified. Twenty-nine patients who had been diagnosed as PKD genetically in seven distinct paediatric haematology departments were evaluated. Fifteen of 23 patients (65.2%) had low PK levels. The PK:hexokinase ratio had 100% sensitivity for PKD diagnosis, superior to PK enzyme assay. Two novel intronic variants (c.695-1G>A and c.694+43C>T) have been described. PKD should be suspected in patients with chronic non-spherocytic haemolytic anaemia, even if enzyme levels are falsely normal. Total PKLR gene sequencing is necessary for the characterization of patients with PKD and for genetic counselling.

Diagnosis and management of pyruvate kinase deficiency: international expert guidelines

Pyruvate kinase (PK) deficiency is the most common cause of chronic congenital non-spherocytic haemolytic anaemia worldwide, with an estimated prevalence of one in 100 000 to one in 300 000 people. PK deficiency results in chronic haemolytic anaemia, with wide ranging and serious consequences affecting health, quality of life, and mortality. The goal of the International Guidelines for the Diagnosis and Management of Pyruvate Kinase Deficiency was to develop evidence-based guidelines for the clinical care of patients with PK deficiency. These clinical guidelines were developed by use of GRADE methodology and the AGREE II framework. Experts were invited after consideration of area of expertise, scholarly contributions in PK deficiency, and country of practice for global representation. The expert panel included 29 expert physicians (including adult and paediatric haematologists and other subspecialists), geneticists, laboratory specialists, nurses, a guidelines methodologist, patients with PK deficiency, and caregivers from ten countries. Five key topic areas were identified, the panel prioritised key questions, and a systematic literature search was done to generate evidence summaries that were used in the development of draft recommendations. The expert panel then met in person to finalise and vote on recommendations according to a structured consensus procedure. Agreement of greater than or equal to 67% among the expert panel was required for inclusion of a recommendation in the final guideline. The expert panel agreed on 31 total recommendations across five key topics: diagnosis and genetics, monitoring and management of chronic complications, standard management of anaemia, targeted and advanced therapies, and special populations. These new guidelines should facilitate best practices and evidence-based PK deficiency care into clinical practice.

Clinical outcome and genotype analysis of four Chinese children with pyruvate kinase deficiency

BACKGROUND

Pyruvate kinase deficiency (PKD) is a rare congenital hemolytic anemia. Here, we summarized the clinical features and laboratory examinations of four Chinese children with PKD and analyze genomic mutations.

METHOD

Collected and analyzed the clinical data of all children and their parents and completed the relevant laboratory examinations of all children. Analyzed the sequences of related genes in children by second-generation sequencing technology and verified the suspected mutations in children's family by Sanger sequencing method or second-generation sequencing technology.

RESULTS

A total of six mutations in gene PKLR were detected in four cases. Except for c.1510C>T (P1) and c.941T>C (P2 and P4), which had been reported in previous studies, the other four novel gene mutations were reported for the first time, including a rare homozygous mutation with large fragment deletion. All those gene mutations cause changes in the amino acids encoded by the gene, as well as subsequent changes in protein structure or loss of function.

CONCLUSION

Compound heterozygous or homozygous mutations in the coding region of PKLR gene are the causes of PKD in these four Chinese children. The second-generation sequencing technology is an effective means to diagnose PKD. The mutations of c.457-c.462delATCGCC, c.1297T>C, c.1096C>T and Exon4-10del of PKLR reported in this article have not been included in the Thousand Genome Database, dbSNP(v138) and ExAC Database. The PKLR gene mutations found in these children with PKD can provide references for further research of the genetic characteristics of PKD and subsequent gene therapy.

Oxidative Stress in Healthy and Pathological Red Blood Cells

Red cell diseases encompass a group of inherited or acquired erythrocyte disorders that affect the structure, function, or production of red blood cells (RBCs). These disorders can lead to various clinical manifestations, including anemia, hemolysis, inflammation, and impaired oxygen-carrying capacity. Oxidative stress, characterized by an imbalance between the production of reactive oxygen species (ROS) and the antioxidant defense mechanisms, plays a significant role in the pathophysiology of red cell diseases. In this review, we discuss the most relevant oxidant species involved in RBC damage, the enzymatic and low molecular weight antioxidant systems that protect RBCs against oxidative injury, and finally, the role of oxidative stress in different red cell diseases, including sickle cell disease, glucose 6-phosphate dehydrogenase deficiency, and pyruvate kinase deficiency, highlighting the underlying mechanisms leading to pathological RBC phenotypes.

Neonatal Thrombocytopenia as a Presenting Finding in de novo Pyruvate Kinase Deficiency

Thrombocytopenia is a common laboratory abnormality encountered in critically ill neonates. The broad differential for thrombocytopenia, and its association with potentially severe neonatal pathology, often presents a diagnostic dilemma prompting extensive evaluation. Hemolysis due to red cell enzymopathies is a rare cause of neonatal thrombocytopenia that is typically brief and self-limiting. Here, we present a case of thrombocytopenia, refractory to transfusion, associated with anemia and hyperbilirubinemia in a neonate with pyruvate kinase deficiency (PKD) arising from compound heterozygous PKLR mutations. The nature of the thrombocytopenia in this patient created considerable diagnostic uncertainty, which was ultimately resolved by whole-exome sequencing. This case emphasizes that inherited red cell defects, such as PKD, are important to consider in cases of neonatal thrombocytopenia.

Association of PKLR gene copy number, expression levels and enzyme activity with 2,3,7,8-TCDD exposure in individuals exposed to Agent Orange/Dioxin in Vietnam

2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) is the most toxic congener of dioxin and has serious long-term effects on the environment and human health. Pyruvate Kinase L/R (PKLR) gene expression levels and gene variants are associated with pyruvate kinase enzyme deficiency, which has been identified as the cause of several diseases linked to dioxin exposure. In this study, we estimated PKLR gene copy number and gene expression levels using real-time quantitative PCR (RT-qPCR) assays, genotyped PKLR SNP rs3020781 by Sanger sequencing, and quantified plasma pyruvate kinase enzyme activity in 100 individuals exposed to Agent Orange/Dioxin near Bien Hoa and Da Nang airfields in Vietnam and 100 healthy controls. The means of PKLR copy numbers and PKLR gene expression levels were significantly higher, while pyruvate kinase enzyme activity was significantly decreased in Agent Orange/Dioxin-exposed individuals compared to healthy controls (P < 0.0001). Positive correlations of PKLR gene copy number and gene expression with 2,3,7,8-TCDD concentrations were observed (r = 0.2, P = 0.045 and r = 0.54, P < 0.0001, respectively). In contrast, pyruvate kinase enzyme activity was inversely correlated with 2,3,7,8-TCDD concentrations (r = -0.52, P < 0.0001). PKLR gene copy number and gene expression levels were also inversely correlated with pyruvate kinase enzyme activity. Additionally, PKLR SNP rs3020781 was found to be associated with 2,3,7,8-TCDD concentrations and PKLR gene expression. In conclusion, PKLR copy number, gene expression levels, and pyruvate kinase enzyme activity are associated with 2,3,7,8-TCDD exposure in individuals living in Agent Orange/Dioxin-contaminated areas.

PYK-SubstitutionOME: an integrated database containing allosteric coupling, ligand affinity and mutational, structural, pathological, bioinformatic and computational information about pyruvate kinase isozymes

Interpreting changes in patient genomes, understanding how viruses evolve and engineering novel protein function all depend on accurately predicting the functional outcomes that arise from amino acid substitutions. To that end, the development of first-generation prediction algorithms was guided by historic experimental datasets. However, these datasets were heavily biased toward substitutions at positions that have not changed much throughout evolution (i.e. conserved). Although newer datasets include substitutions at positions that span a range of evolutionary conservation scores, these data are largely derived from assays that agglomerate multiple aspects of function. To facilitate predictions from the foundational chemical properties of proteins, large substitution databases with biochemical characterizations of function are needed. We report here a database derived from mutational, biochemical, bioinformatic, structural, pathological and computational studies of a highly studied protein family-pyruvate kinase (PYK). A centerpiece of this database is the biochemical characterization-including quantitative evaluation of allosteric regulation-of the changes that accompany substitutions at positions that sample the full conservation range observed in the PYK family. We have used these data to facilitate critical advances in the foundational studies of allosteric regulation and protein evolution and as rigorous benchmarks for testing protein predictions. We trust that the collected dataset will be useful for the broader scientific community in the further development of prediction algorithms. Database URL https://github.com/djparente/PYK-DB.

Updates and advances in pyruvate kinase deficiency

Mutations in the PKLR gene lead to pyruvate kinase (PK) deficiency, causing chronic hemolytic anemia secondary to reduced red cell energy, which is crucial for maintenance of the red cell membrane and function. Heterogeneous clinical manifestations can result in significant morbidity and reduced health-related quality of life. Treatment options have historically been limited to supportive care, including red cell transfusions and splenectomy. Current disease-modifying treatment considerations include an oral allosteric PK activator, mitapivat, which was recently approved for adults with PK deficiency, and gene therapy, which is currently undergoing clinical trials. Studies evaluating the role of PK activators in other congenital hemolytic anemias are ongoing. The long-term effect of treatment with disease-modifying therapy in PK deficiency will require continued evaluation.

The Pyruvate Kinase Deficiency Global Longitudinal (Peak) Registry: rationale and study design

INTRODUCTION

Pyruvate kinase (PK) deficiency is a rare, under-recognised, hereditary condition that leads to chronic haemolytic anaemia and potentially serious secondary complications, such as iron overload, cholecystitis, pulmonary hypertension and extramedullary haematopoiesis. It is an autosomal recessive disease caused by homozygous or compound heterozygous mutations in the PKLR gene. Due to its rarity and clinical heterogeneity, information on the natural history and long-term clinical course of PK deficiency is limited, presenting major challenges to patient management, the development of new therapies and establishing disease-specific treatment recommendations. The Pyruvate Kinase Deficiency Global Longitudinal (Peak) Registry is an initiative to address the gaps in the knowledge of PK deficiency. This manuscript describes the objectives, study design and methodology for the Peak Registry.

METHODS AND ANALYSIS

The Peak Registry is an observational, longitudinal, global registry of adult and paediatric patients with a genetically confirmed diagnosis of PK deficiency. The Peak Steering Committee is composed of 11 clinicians and researchers with experience in the diagnosis and management of PK deficiency from 10 countries, a patient representative and representatives from the sponsor (Agios Pharmaceuticals). The registry objective is to foster an understanding of the longitudinal clinical implications of PK deficiency, including its natural history, treatments and outcomes, and variability in clinical care. The aim is to enrol up to 500 participants from approximately 60 study centres across 20 countries over 7 years, with between 2 and 9 years of follow-up. Data will include demographics, diagnosis history, genotyping, transfusion history, relevant clinical events, medications, emergency room visits and hospitalisations.

ETHICS AND DISSEMINATION

Registry protocol and informed consent forms are approved by institutional review boards/independent ethics committees at each study site. The study is being conducted in accordance with the Declaration of Helsinki. Registry data will be published in peer-reviewed journal articles and conference publications.

TRIAL REGISTRATION NUMBER

NCT03481738.

Evaluation of the main regulators of systemic iron homeostasis in pyruvate kinase deficiency

Iron homeostasis and dyserythropoiesis are poorly investigated in pyruvate kinase deficiency (PKD), the most common glycolytic defect of erythrocytes. Herein, we studied the main regulators of iron balance and erythropoiesis, as soluble transferrin receptor (sTfR), hepcidin, erythroferrone (ERFE), and erythropoietin (EPO), in a cohort of 41 PKD patients, compared with 42 affected by congenital dyserythropoietic anemia type II (CDAII) and 50 with hereditary spherocytosis (HS). PKD patients showed intermediate values of hepcidin and ERFE between CDAII and HS, and clear negative correlations between log-transformed hepcidin and log-EPO (Person's r correlation coefficient =  - 0.34), log-hepcidin and log-ERFE (r =  - 0.47), and log-hepcidin and sTfR (r =  - 0.44). sTfR was significantly higher in PKD; EPO levels were similar in PKD and CDAII, both higher than in HS. Finally, genotype-phenotype correlation in PKD showed that more severe patients, carrying non-missense/non-missense genotypes, had lower hepcidin and increased ERFE, EPO, and sTFR compared with the others (missense/missense and missense/non-missense), suggesting a higher rate of ineffective erythropoiesis. We herein investigated the main regulators of systemic iron homeostasis in the largest cohort of PKD patients described so far, opening new perspectives on the molecular basis and therapeutic approaches of this disease.

Targeted next-generation sequencing identifies eighteen novel mutations expanding the molecular and clinical spectrum of PKLR gene disorders in the Indian population

Pyruvate kinase deficiency (PKD) is an autosomal recessive condition, caused due to homozygous or compound heterozygous mutation in the PKLR gene resulting in non-spherocytic hereditary hemolytic anemia. Clinical manifestations in PKD patients vary from moderate to severe lifelong hemolytic anemia either requiring neonatal exchange transfusion or blood transfusion support. Measuring PK enzyme activity is the gold standard approach for diagnosis but residual activity must be related to the increased reticulocyte count. The confirmatory diagnosis is provided by PKLR gene sequencing by conventional as well as targeted next-generation sequencing involving genes associated with enzymopathies, membranopathies, hemoglobinopathies, and bone marrow failure disorders. In this study, we report the mutational landscape of 45 unrelated PK deficiency cases from India. The genetic sequencing of PKLR revealed 40 variants comprising 34 Missense Mutations (MM), 2 Nonsense Mutations (NM), 1 Splice site, 1 Intronic, 1 Insertion, and 1 Large Base Deletion. The 17 novel variants identified in this study are A115E, R116P, A423G, K313I, E315G, E318K, L327P, M377L, A423E, R449G, H507Q, E538K, G563S, c.507 + 1 G > C, c.801_802 ins A (p.Asp268ArgfsTer48), IVS9dsA-T + 3, and one large base deletion. In combination with previous reports on PK deficiency, we suggest c.880G > A, c.943G > A, c.994G > A, c.1456C > T, c.1529G > A are the most frequently observed mutations in India. This study expands the phenotypic and molecular spectrum of PKLR gene disorders and also emphasizes the importance of combining both targeted next-generation sequencing with bioinformatics analysis and detailed clinical evaluation to elaborate a more accurate diagnosis and correct diagnosis for transfusion dependant hemolytic anemia in a cohort of the Indian population.

Prenatal management of fetal anemia due to pyruvate kinase deficiency: A case report

BACKGROUND

Pyruvate Kinase (PK) deficiency is the most common enzyme defect of glycolysis, leading to congenital hemolytic anemia, which can occur during the neonatal period.

STUDY DESIGN AND METHODS

We report the prenatal management of fetal anemia related to PK deficiency in a family with a severe proband.

RESULTS

The couple had a first child born with hydrops, whose PK deficiency was diagnosed at 18 months of life. He was treated with allogeneic bone marrow transplantation. The second child was free from disease. For the third pregnancy, the amniocentesis revealed a PK deficiency. Weekly ultrasound monitoring of the middle cerebral artery velocity allowed the detection of severe fetal anemia. Two intrauterine red blood cell transfusions (IUTs) were performed, raising the fetal hemoglobin from 6.6 to 14.5 g/dl at 28 weeks' gestation and from 8.9 to 15.3 g/dl at 31 weeks. A hematopoietic stem cell allograft was discussed prenatally but not chosen, as it would not have significantly changed the perinatal prognosis. The patient delivered a 2730 g girl at 37 weeks, with hemoglobin of 13.6 g/dl. The child presented with neonatal jaundice treated with phototherapy and received postnatal transfusions.

DISCUSSION

When a proband is identified in a family, fetal investigation is warranted, to set up third-trimester ultrasound surveillance and perinatal management. In case of fetal severe anemia of unknown etiology, the workup on fetal blood sampling before IUT should comprise the search for erythrocytes enzymopathies, such as PK deficiency. IUTs allow safer full-term delivery in cases with PK deficiency.

Genetic Diagnosis of Pyruvate Kinase Deficiency in Undiagnosed Iranian Patients with Severe Hemolytic Anemia, using Whole Exome Sequencing

BACKGROUND

After ruling out the most common causes of severe hemolytic anemia by routine diagnostic tests, certain patients remain without a diagnosis. The aim of this study was to elucidate the genetic cause of the disease in these patients using next generation sequencing (NGS).

METHODS

Four unrelated Iranian families including six blood transfusion dependent cases and their parents were referred to us from a specialist center in Tehran. There was no previous history of anemia in the families and the parents had no abnormal hematological presentations. All probands presented severe congenital hemolytic anemia, neonatal jaundice and splenomegaly. Common causes of hemolytic anemia were ruled out prior to this investigation in these patients and they had no diagnosis. Whole exome sequencing (WES) was performed in the probands and the results were confirmed by Sanger sequencing and subsequent family studies.

RESULTS

We identified five variants in the PKLR gene, including a novel unpublished frameshift in these families. These variants were predicted as pathogenic according to the ACMG guidelines by Intervar and/or Varsome prediction tools. Subsequent family studies by Sanger sequencing supported the diagnosis of pyruvate kinase deficiency (PKD) in six affected individuals and the carrier status of disease in their parents.

CONCLUSION

These findings show that PKD is among the rare blood disorders that could remain undiagnosed or even ruled out in Iranian population without performing NGS. This could be due to pitfalls in clinical, hematological or biochemical approaches in diagnosing PKD. Furthermore, genotyping PKD patients in Iran could reveal novel mutations in the PKLR gene.

Pyruvate Kinase Deficiency: Current Challenges and Future Prospects

Pyruvate kinase deficiency (PKD) is a rare autosomal recessive disease marked by chronic hemolytic anemia of various severity and frequent complications including gallstones, splenomegaly, iron overload, and others. Disease phenotype is highly heterogeneous and changes over time with children, adolescents and adult patients displaying different transfusion requirement and rates of complications. The diagnosis relies on the initial clinical suspicion in a patient with chronic hemolysis and exclusion of other more common congenital forms of hemolytic anemias; it is supported by the demonstration of reduced PK enzyme activity, and further confirmed by the detection of (homozygous or compound heterozygous) mutations of PKLR gene. Therapy is mainly supportive, with vitamin supplementation and transfusions (based on symptoms and patient growth rather than on fixed Hb thresholds). Splenectomy is widely performed, although it is less effective than in membrane defects and carries thrombotic and infectious risk. In the last decade, the allosteric PK enzyme activator mitapivat showed dramatic clinical benefit in clinical trials and gene therapy is also being studied to substitute the defective enzyme. In this review, we provide an insight in the current challenges of PKD diagnosis and management and discuss the future application of novel drugs and gene therapy, including a focus on quality of life.

Diagnosis, monitoring, and management of pyruvate kinase deficiency in children

Pyruvate kinase (PK) deficiency is a rare, congenital red blood cell disorder caused by a single gene defect. The spectrum of genotypes, variants, and phenotypes are broad, commonly requiring a multimodal approach including enzyme and genetic testing for accurate and reliable diagnosis. Similarly, management of primary and secondary sequelae of PK deficiency varies, mainly including supportive care with transfusions and surgical interventions to improve symptoms and quality of life. Given the risk of acute and long-term complications of PK deficiency and its treatment, regular monitoring and management of iron burden and organ dysfunction is critical. Therefore, all children and adolescents with PK deficiency should receive regular hematology care with visits at least every 6 months regardless of transfusion status. We continue to learn more about the spectrum of symptoms and complications of PK deficiency and best practice for monitoring and management through registry efforts (NCT03481738). The treatment of PK deficiency has made strides over the last few years with newer disease-modifying therapies being developed and studied, with the potential to change the course of disease in childhood and beyond.

Novel Compound Heterozygous PKLR Mutation Induced Pyruvate Kinase Deficiency With Persistent Pulmonary Hypertension in a Neonate: A Case Report

Background

Pulmonary hypertension could be associated with pyruvate kinase deficiency (PKD). There are few reported cases of PPHN as the first clinical manifestation of PKD. Herein we report a rare case of PKD in which the patient exhibited persistent pulmonary hypertension in the neonate (PPHN), and genetic testing helped to rapidly identify an potential association.

Case presentation

The patient was a newborn boy who suffered from severe dyspnea, extreme anemia, skin pallor, and hypoxemia. Repeated echocardiography indicated persistent severe pulmonary hypertension with a calculated pulmonary artery pressure of 75 mmHg, and right ventricular hypertrophy. The administration of nitric oxide significantly reduced the pulmonary artery pressure. Whole-exome sequencing revealed a compound heterozygous mutation consisting of c.707T > G and c.826_827insAGGAGCATGGGG. PolyPhen_2 and MutationTaster indicated that both the c.707T > G (probability 0.999) and c.826_827insAGGAGCATGGGG (probability 0.998) mutations were disease causing. PROVEAN protein batch analysis indicated that the associated p.L236R region was deleterious (score −4.71) and damaging (SIFT prediction 0.00), and this was also the case for p.G275_V276insEEHG (deleterious score −12.00, SIFT prediction 0.00). Substantial structural changes in the transport domain of the protein were predicted using SWISS-MODEL, and indicated that both mutations led to an unstable protein structure. Thus, a novel compound heterozygous mutation of PKLR-induced PKD with PPHN was diagnosed.

Conclusion

The current study suggests that molecular genetic screening is useful for identifying PPHN, particularly in children with metabolic disorders. In patients exhibiting unexplained hyperbilirubinemia combined with severe pulmonary hypertension, PKD might be a potential possible alternative explanation. Genetic screening is helpful for identifying genetic causes of pulmonary hypertension, especially in patients with PPHN. This report expands the mutation spectrum of the PKLR gene, and contributes to the genotype-phenotype map of PKD.

Mitapivat versus Placebo for Pyruvate Kinase Deficiency

BACKGROUND

Pyruvate kinase deficiency is a rare, hereditary, chronic condition that is associated with hemolytic anemia. In a phase 2 study, mitapivat, an oral, first-in-class activator of erythrocyte pyruvate kinase, increased the hemoglobin level in patients with pyruvate kinase deficiency.

METHODS

In this global, phase 3, randomized, placebo-controlled trial, we evaluated the efficacy and safety of mitapivat in adults with pyruvate kinase deficiency who were not receiving regular red-cell transfusions. The patients were assigned to receive either mitapivat (5 mg twice daily, with potential escalation to 20 or 50 mg twice daily) or placebo for 24 weeks. The primary end point was a hemoglobin response (an increase from baseline of ≥1.5 g per deciliter in the hemoglobin level) that was sustained at two or more scheduled assessments at weeks 16, 20, and 24. Secondary efficacy end points were the average change from baseline in the hemoglobin level, markers of hemolysis and hematopoiesis, and the change from baseline at week 24 in two pyruvate kinase deficiency-specific patient-reported outcome measures.

RESULTS

Sixteen of the 40 patients (40%) in the mitapivat group had a hemoglobin response, as compared with none of the 40 patients in the placebo group (adjusted difference, 39.3 percentage points; 95% confidence interval, 24.1 to 54.6; two-sided P<0.001). Patients who received mitapivat had a greater response than those who received placebo with respect to each secondary end point, including the average change from baseline in the hemoglobin level. The most common adverse events were nausea (in 7 patients [18%] in the mitapivat group and 9 patients [23%] in the placebo group) and headache (in 6 patients [15%] and 13 patients [33%], respectively). Adverse events of grade 3 or higher occurred in 10 patients (25%) who received mitapivat and 5 patients (13%) who received placebo.

CONCLUSIONS

In patients with pyruvate kinase deficiency, mitapivat significantly increased the hemoglobin level, decreased hemolysis, and improved patient-reported outcomes. No new safety signals were identified in the patients who received mitapivat. (Funded by Agios Pharmaceuticals; ACTIVATE ClinicalTrials.gov number, NCT03548220.).

Case report: Compound heterozygosity in PKLR gene with a large exon deletion and a novel rare p.Gly536Asp variant as a cause of severe pyruvate kinase deficiency

Red cell pyruvate kinase (PK) deficiency is the most common cause of hereditary nonspherocytic hemolytic anemia and the most frequent enzyme abnormality of the glycolytic pathway. To the best of our knowledge, this is the first Korean PK deficiency study that analyzes copy number variation (CNV) using next-generation sequencing (NGS). A 7-year-old girl with jaundice was admitted for evaluation of a persistent hemolytic anemia. The proband appeared chronically ill, showing a yellowish skin color, icteric sclera, hepatomegaly, and splenomegaly on physical examination. Sequence variants and CNV generated from NGS data were estimated to determine if there was a potential genetic cause. As a result, compound heterozygosity in the PKLR gene for a large exon deletion between exon 3 and exon 9 accompanied with a novel rare p.Gly536Asp variant located on exon 10 was identified as a cause of severe PK deficiency in the proband. The PK activity of the proband had been measured at the time of day 1, 21, and 28 after receiving transfusion to indirectly assume the effect of the transfused blood, and the results were 100.9%, 73.0%, and 48.5%, compared with average of normal controls, respectively. Our report emphasizes the need to perform complete CNV analysis of NGS data and gene dosage assays such as multiplex ligation-dependent probe amplification to evaluate large deletions or duplications/insertions of the PKLR gene in patients with suspected PK deficiency.

Mitapivat, a novel pyruvate kinase activator, for the treatment of hereditary hemolytic anemias

Mitapivat (AG-348) is a novel, first-in-class oral small molecule allosteric activator of the pyruvate kinase enzyme. Mitapivat has been shown to significantly upregulate both wild-type and numerous mutant forms of erythrocyte pyruvate kinase (PKR), increasing adenosine triphosphate (ATP) production and reducing levels of 2,3-diphosphoglycerate. Given this mechanism, mitapivat has been evaluated in clinical trials in a wide range of hereditary hemolytic anemias, including pyruvate kinase deficiency (PKD), sickle cell disease, and the thalassemias. The clinical development of mitapivat in adults with PKD is nearly complete, with the completion of two successful phase III clinical trials demonstrating its safety and efficacy. Given these findings, mitapivat has the potential to be the first approved therapeutic for PKD. Mitapivat has additionally been evaluated in a phase II trial of patients with alpha- and beta-thalassemia and a phase I trial of patients with sickle cell disease, with findings suggesting safety and efficacy in these more common hereditary anemias. Following these successful early-phase trials, two phase III trials of mitapivat in thalassemia and a phase II/III trial of mitapivat in sickle cell disease are beginning worldwide. Promising preclinical studies have additionally been done evaluating mitapivat in hereditary spherocytosis, suggesting potential efficacy in erythrocyte membranopathies as well. With convenient oral dosing and a safety profile comparable with placebo in adults with PKD, mitapivat is a promising new therapeutic for several hereditary hemolytic anemias, including those without any currently US Food and Drug Administration (FDA) or European Medicines Agency (EMA)-approved drug therapies. This review discusses the preclinical studies, pharmacology, and clinical trials of mitapivat.

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.

Untargeted metabolic profiling in dried blood spots identifies disease fingerprint for pyruvate kinase deficiency

The diagnostic evaluation and clinical characterization of rare hereditary anemia (RHA) is to date still challenging. In particular, there is little knowledge on the broad metabolic impact of many of the molecular defects underlying RHA. In this study we explored the potential of untargeted metabolomics to diagnose a relatively common type of RHA: Pyruvate Kinase Deficiency (PKD). In total, 1903 unique metabolite features were identified in dried blood spot samples from 16 PKD patients and 32 healthy controls. A metabolic fingerprint was identified using a machine learning algorithm, and subsequently a binary classification model was designed. The model showed high performance characteristics (AUC 0.990, 95%CI 0.981-0.999) and an accurate class assignment was achieved for all newly added control (13) and patient samples (6), with the exception of one patient (accuracy 94%). Important metabolites in the metabolic fingerprint included glycolytic intermediates, polyamines and several acyl carnitines. In general, the application of untargeted metabolomics in dried blood spots is a novel functional tool that holds promise for diagnostic stratification and studies on disease pathophysiology in RHA.

[Consensus document for the diagnosis and treatment of pyruvate kinase deficiency]

Pyruvate kinase (PK) deficiency is the second most frequent enzymopathy and the most common cause of chronic hereditary non-spherocytic haemolytic anaemia. Its global prevalence is underestimated due to low clinical suspicion of mild cases, associated with difficulties in the performance and interpretation of PK enzymatic activity assays. With the advent of next generation sequencing techniques, a better diagnostic approach is achieved. Treatment remains based on red blood cell transfusions and splenectomy, with special attention to iron overload, not only in transfusion-dependent patients. Nowadays, allogeneic hematopoietic stem cell transplantation is the only curative treatment, recommended only in selected cases of severely affected patients with an HLA-identical donor. Novel pharmacological and gene therapies are in clinical trials, with promising results. In this article, the Spanish Erythropathology Group reviews the current situation of PK deficiency, paying special attention to the usefulness of different diagnostic techniques and to actual and emerging treatments.

Health-Related Quality of Life and Fatigue in Children and Adults with Pyruvate Kinase Deficiency

The impact of PKD on HRQoL and fatigue is described in 254 children and adults using 6 validated instruments.

Severe anemia, regular transfusion, iron chelation, and nonmissense mutations are associated with worse patient-reported outcomes.

Pyruvate kinase deficiency (PKD) is the most common cause of congenital nonspherocytic hemolytic anemia. Although recognition of the disease spectrum has recently expanded, data describing its impact on health-related quality of life (HRQoL) are limited. In this prospective international cohort of 254 patients (131 adults and 123 children) with PKD, we used validated measures to assess the impact of disease on HRQoL (EuroQol 5-Dimension Questionnaire, Pediatric Quality of Life Inventory Generic Core Scale version 4.0, and Functional Assessment of Cancer Therapy-Anemia) and fatigue (Patient Reported Outcomes Measurement Information System Fatigue and Pediatric Functional Assessment of Chronic Illness Therapy-Fatigue). Significant variability in HRQoL and fatigue was reported for adults and children, although individual scores were stable over a 2-year interval. Although adults who were regularly transfused reported worse HRQoL and fatigue compared with those who were not (EuroQol-visual analog scale, 58 vs 80; P = .01), this difference was not seen in children. Regularly transfused adults reported lower physical, emotional, and functional well-being and more anemia symptoms. HRQoL and fatigue significantly differed in children by genotype, with the worst scores in those with 2 severe PKLR mutations; this difference was not seen in adults. However, iron chelation was associated with significantly worse HRQoL scores in children and adults. Pulmonary hypertension was also associated with significantly worse HRQoL. Additionally, 59% of adults and 35% of children reported that their jaundice upset them, identifying this as an important symptom for consideration. Although current treatments for PKD are limited to supportive care, new therapies are in clinical trials. Understanding the impact of PKD on HRQoL is important to assess the utility of these treatments. This trial was registered at www.clinicaltrials.gov as #NCT02053480.

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).

Complex Modes of Inheritance in Hereditary Red Blood Cell Disorders: A Case Series Study of 155 Patients

Hereditary erythrocytes disorders include a large group of conditions with heterogeneous molecular bases and phenotypes. We analyzed here a case series of 155 consecutive patients with clinical suspicion of hereditary erythrocyte defects referred to the Medical Genetics Unit from 2018 to 2020. All of the cases followed a diagnostic workflow based on a targeted next-generation sequencing panel of 86 genes causative of hereditary red blood cell defects. We obtained an overall diagnostic yield of 84% of the tested patients. Monogenic inheritance was seen for 69% (107/155), and multi-locus inheritance for 15% (23/155). PIEZO1 and SPTA1 were the most mutated loci. Accordingly, 16/23 patients with multi-locus inheritance showed dual molecular diagnosis of dehydrated hereditary stomatocytosis/xerocytosis and hereditary spherocytosis. These dual inheritance cases were fully characterized and were clinically indistinguishable from patients with hereditary spherocytosis. Additionally, their ektacytometry curves highlighted alterations of dual inheritance patients compared to both dehydrated hereditary stomatocytosis and hereditary spherocytosis. Our findings expand the genotypic spectrum of red blood cell disorders and indicate that multi-locus inheritance should be considered for analysis and counseling of these patients. Of note, the genetic testing was crucial for diagnosis of patients with a complex mode of inheritance.

Rare anemias in adolescents

Anemia can be the consequence of a single disease or an expression of external factors mainly nutritional deficiencies. Genetic issues are important in the primary care of adolescents because a genetic diagnosis may not be made until adolescence when the teenager presents with the first signs or symptoms of the condition. This situation is relatively frequent for rare anemias (RA) an important, and relatively heterogeneous group of rare diseases (RD) where anemia is the first and most relevant clinical manifestation of the disease. RA are characterized by their low prevalence (< 1 per 10,000 individuals), and, in some cases, by their complex mechanism. For these reasons, RA are little known, even among health professionals, and patients tend to remain undiagnosed or misdiagnosed for long periods of time, making it impossible to know the prognosis of the disease or to carry out genetic counseling for future pregnancies. Since this situation is an important cause of anxiety for both adolescent patients and their families, the physician's knowledge of the natural history of a genetic disease will be the key factor for the anticipatory guidance for diagnosis and clinical follow-up. RA can be due to three primary causes: 1.Bone marrow erythropoietic defects, 2. Excessive destruction of mature red blood cells (hemolysis), and 3. Blood loss (bleeding). More than 80% of RAs are hereditary, and about 20% remain undiagnosed but when their first clinical manifestations appear during childhood or adolescence, they are frequently misdiagnosed with iron deficiency. For this reason, RA are today an important clinical and social health problem worldwide.

A Proposed Concept for Defective Mitophagy Leading to Late Stage Ineffective Erythropoiesis in Pyruvate Kinase Deficiency

Pyruvate kinase deficiency (PKD) is a rare congenital hemolytic anemia caused by mutations in the PKLR gene. Here, we review pathophysiological aspects of PKD, focusing on the interplay between pyruvate kinase (PK)-activity and reticulocyte maturation in the light of ferroptosis, an iron-dependent process of regulated cell death, and in particular its key player glutathione peroxidase 4 (GPX4). GPX4 plays an important role in mitophagy, the key step of peripheral reticulocyte maturation and GPX4 deficiency in reticulocytes results in a failure to fully mature. Mitophagy depends on lipid oxidation, which is under physiological conditions controlled by GPX4. Lack of GPX4 leads to uncontrolled auto-oxidation, which will disrupt autophagosome maturation and thereby perturb mitophagy. Based on our review, we propose a model for disturbed red cell maturation in PKD. A relative GPX4 deficiency occurs due to glutathione (GSH) depletion, as cytosolic L-glutamine is preferentially used in the form of α-ketoglutarate as fuel for the tricarboxylic acid (TCA) cycle at the expense of GSH production. The relative GPX4 deficiency will perturb mitophagy and, subsequently, results in failure of reticulocyte maturation, which can be defined as late stage ineffective erythropoiesis. Our hypothesis provides a starting point for future research into new therapeutic possibilities, which have the ability to correct the oxidative imbalance due to lack of GPX4.

Comorbidities and complications in adults with pyruvate kinase deficiency

Objectives

Pyruvate kinase (PK) deficiency is caused by PKLR gene mutations, leading to defective red blood cell glycolysis and hemolytic anemia. Rates of comorbidities and complications by transfusion history and relative to the general population remain poorly quantified.

Methods

Data for patients aged ≥ 18 years with two confirmed PKLR mutations were obtained from the PK deficiency Natural History Study (NCT02053480). Frequencies of select conditions were compared with an age‐ and sex‐matched cohort from a general insured US population without PK deficiency.

Results

Compared with the matched population (n = 1220), patients with PK deficiency (n = 122) had significantly higher lifetime rates of osteoporosis, liver cirrhosis, and pulmonary hypertension; splenectomy and cholecystectomy rates were also significantly higher in the 8 years before the index date. Sixty‐five (53.3%) patients with PK deficiency were classified as regularly transfused, 30 (24.6%) as occasionally transfused, and 27 (22.1%) as never transfused. Regularly transfused patients were significantly more likely than never transfused patients to have had splenectomy, cholecystectomy, and/or thrombosis. Liver iron overload was reported in 62% of patients and occurred regardless of transfusion cohort.

Conclusions

Even never transfused patients with PK deficiency had higher rates of select comorbidities and complications than individuals without PK deficiency.

Erythrocytes as a preferential target of oxidative stress in blood

Red blood cells (RBC) are specifically differentiated to transport oxygen and carbon dioxide in the blood and they lack most organelles, including mitochondria. The autoxidation of hemoglobin constitutes a major source of reactive oxygen species (ROS). Nitric oxide, which is produced by endothelial nitric oxide synthase (NOS3) or via the hemoglobin-mediated conversion of nitrite, interacts with ROS and results in the production of reactive nitrogen oxide species. Herein we present an overview of anemic diseases that are closely related to oxidative damage. Because the compensation of proteins by means of gene expression does not proceed in enucleated cells, antioxidative and redox systems play more important roles in maintaining the homeostasis of RBC against oxidative insult compared to ordinary cells. Defects in hemoglobin and enzymes that are involved in energy production and redox reactions largely trigger oxidative damage to RBC. The results of studies using genetically modified mice suggest that antioxidative enzymes, notably superoxide dismutase 1 and peroxiredoxin 2, play essential roles in coping with oxidative damage in erythroid cells, and their absence limits erythropoiesis, the life-span of RBC and consequently results in the development of anemia. The degeneration of the machinery involved in the proteolytic removal of damaged proteins appears to be associated with hemolytic events. The ubiquitin-proteasome system is the dominant machinery, not only for the proteolytic removal of damaged proteins in erythroid cells but also for the development of erythropoiesis. Hence, despite the fact that it is less abundant in RBC compared to ordinary cells, the aberrant ubiquitin-proteasome system may be associated with the development of anemic diseases via the accumulation of damaged proteins, as typified in sickle cell disease, and impaired erythropoiesis.

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.

A Family Affected by a Life-Threatening Erythrocyte Defect Caused by Pyruvate Kinase Deficiency With Normal Iron Status: A Case Report

Background

Red cell pyruvate kinase deficiency (PKD) is a defect of glycolysis causing congenital non-spherocytic hemolytic anemia. PKD is transmitted as an autosomal recessive trait. The clinical features of PKD are highly variable, from mild to life-threatening anemia which can lead to death in the neonatal period. Most patients with PKD must receive regular transfusions in early childhood and as a consequence suffer from iron overloading.

Patient

Here, we report a Polish family with life-threatening hemolytic anemia of unknown etiology. Whole exome sequencing identified two heterozygous mutations, c.1529 G > A (p.R510Q) and c.1495 T > C (p.S499P) in the PKLR gene. Molecular modeling showed that the both PKLR mutations are responsible for major disturbance of the protein structure and functioning. Despite frequent transfusions the patients do not show any signs of iron overload and hepcidin, a major regulator of iron uptake, is undetectable in their serum. The patients were homozygous for the rs855791 variant of the TMPRSS6 gene which has earlier been shown to down-regulate iron absorption and accumulation.

Conclusion

The lack of iron overload despite a reduced level of hepcidin in two transfusion-dependent PKD patients suggests the existence of a hepcidin-independent mechanism of iron regulation preventing iron overloading.

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.

Prevalence of pyruvate kinase deficiency: A systematic literature review

OBJECTIVES

Pyruvate kinase deficiency (PK deficiency) is a rare disorder caused by compound heterozygosity or homozygosity for > 300 mutations in the PKLR gene. To understand PK deficiency prevalence, we conducted a systematic literature review.

METHODS

We queried Embase and Medline for peer-reviewed references reporting PK deficiency prevalence/incidence, PKLR mutant allele frequency (MAF) among the general population, or crude results from which these metrics could be derived.

RESULTS

Of 1390 references screened, 1296 were excluded after title/abstract review; 60 were excluded after full-text review. Four of the remaining 34 studies were considered high-quality for estimating PK deficiency prevalence. Two high-quality studies identified cases from source populations of known sizes, producing estimates of diagnosed PK deficiency prevalence of 3.2 and 8.5 per million. Another high-quality study derived an estimate of diagnosed PK deficiency prevalence of 6.5 per million by screening jaundiced newborns. The final high-quality study estimated total diagnosed and undiagnosed PK deficiency prevalence to be 51 per million through extrapolation from observed MAFs.

CONCLUSIONS

We conclude that prevalence of clinically diagnosed PK deficiency is likely between 3.2 and 8.5 per million in Western populations, while the prevalence of diagnosed and undiagnosed PK deficiency could possibly be as high as 51 per million.

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.

Trends in the Development of Diagnostic Tools for Red Blood Cell-Related Diseases and Anemias

In the recent years, the progress in genetic analysis and next-generation sequencing technologies have opened up exciting landscapes for diagnosis and study of molecular mechanisms, allowing the determination of a particular mutation for individual patients suffering from hereditary red blood cell-related diseases or anemia. However, the huge amount of data obtained makes the interpretation of the results and the identification of the pathogenetic variant responsible for the diseases sometime difficult. Moreover, there is increasing evidence that the same mutation can result in varying cellular properties and different symptoms of the disease. Even for the same patient, the phenotypic expression of the disorder can change over time. Therefore, on top of genetic analysis, there is a further request for functional tests that allow to confirm the pathogenicity of a molecular variant, possibly to predict prognosis and complications (e.g., vaso-occlusive pain crises or other thrombotic events) and, in the best case, to enable personalized theranostics (drug and/or dose) according to the disease state and progression. The mini-review will reflect recent and future directions in the development of diagnostic tools for red blood cell-related diseases and anemias. This includes point of care devices, new incarnations of well-known principles addressing physico-chemical properties, and interactions of red blood cells as well as high-tech screening equipment and mobile laboratories.