Severe Transfusion-dependent Hemolytic Anemia Research Articles

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.

Rapid Identification of Biallelic SPTB Mutation in a Neonate with Severe Congenital Hemolytic Anemia and Liver Failure

Heterozygous pathogenic variants in SPTB cause autosomal dominant hereditary spherocytosis, an important cause of neonatal nonimmune hemolytic anemia. Biallelic mutations are rarely reported, all with severe neonatal presentation. We describe rapid (68 h) genomic diagnosis of homozygous β-spectrin deficiency in a newborn with severe transfusion-dependent hemolytic anemia, conjugated hyperbilirubinemia, and progressive liver failure. Trio whole-exome sequencing identified a novel biallelic SPTB variant (c.6119C>T; p.Thr2040Ile) located in the critical spectrin repeat region. Pretransfusion blood film showed marked spherocytosis including microspherocytes and nucleated erythrocytes, and eosin-5-maleimide (E5M) staining was markedly reduced, supporting pathogenicity. Both asymptomatic heterozygous parents demonstrated mildly reduced E5M staining, with occasional spherocytes and elliptocytes. Early molecular diagnosis facilitated hypertransfusion to suppress ineffective erythropoiesis and reverse hepatic dysfunction. This report broadens the genotypic and phenotypic spectrum of spectrin deficiency and highlights the utility of rapid genomic testing in facilitating early diagnosis and informing targeted therapy in critically ill patients.

An integration-free iPSC line (MUSIi008-A) derived from a patient with severe hemolytic anemia carrying compound heterozygote mutations in KLF1 gene for disease modeling

We generated an induced pluripotent stem cell (iPSC) line from peripheral blood mononuclear cells (PBMNCs) isolated from a 1-year old female carrying compound heterozygote for KLF1 mutations (G176RfsX179 and A298P mutations). Non-integrating Sendai viral (SeV) vectors containing KOS, hc-MYC and hKLF4 were used for reprogramming. The established MUSIi008-A cell line contained the same mutations found in the patient, expressed pluripotent markers, differentiated into cells of three embryonic germ layers both in vitro and in vivo, and exhibited normal karyotype. This cell line may provide an alternative renewable source of cells for in vitro disease modeling of severe transfusion-dependent hemolytic anemia.

The Spectrum of Genetic Defects in Indian Patients with Rare Congenital Anemias: Next Generation Sequencing Based Approach

IntroductionDiagnosis of inherited anemias is based on automated red cell indices, morphology and reticulocyte count in an appropriate clinical presentation and a stepwise diagnostic algorithm needs to be followed. Major inherited causes of hemolysis include the hemoglobinopathies, membranopathies and enzymopathies. In contrast, ineffective erythropoiesis, a term that refers to a disturbance in proliferation, differentiation and maturation of erythroblasts, includes megaloblastic anemia, myelodysplastic syndromes, thalassemias, and congenital dyserythropoietic anemias (CDA). Phenotypes vary from severe transfusion-dependent hemolytic anemia (HA) to fully compensated hemolysis. Patients are encountered where the entire spectrum of diagnostic tests cannot identify the etiology. Causal genes implicated are numerous, making a gene-by-gene approach time consuming, expensive and laborious. Hence, the use of targeted resequencing can expedite molecular diagnosis, genetic counseling and prenatal diagnosis if indicated.ObjectivesThis study aimed at determining the spectrum of mutations in uncommon HA and CDA.MethodsSixty-one patients (HA=44, CDA=17) with clinical and laboratory evidence suggestive of HA/CDA were enrolled after excluding common causes of anemias. Various biochemical and molecular tests were used to exclude glucose-6-phosphate dehydrogenase (G6PD) deficiency, hemoglobinopathies, autoimmune HA, hereditary spherocytosis and pyruvate kinase (PK) deficiency. Peripheral blood genomic DNA was extracted using QIAamp DNA Blood Midi Kit, quantified on NanoDrop 2000 spectrophotometer and Qubit® 2.0 Fluorometer. Common G6PD, PKLR variants, SEC23B mutation were excluded by molecular tests. Since the genetic defects in Indian patients with unexplained HA/CDA are not available, we first tested 16 patients with a comprehensive commercially available sequencing panel that covers 4,813 clinically-relevant genes. We next sought to streamline testing and designed a customized panel of 55 genes (Illumina). Variants were annotated and classified and the most likely disease-causing variants were validated by Sanger sequencing in the patient and available affected and unaffected family members.ResultsOut of 61 patient's sequenced, unexpected pyruvate kinase (PK) deficiency were found in 11 patients. PK enzyme activity assay was within normal limits in all these cases. Three patients with G6PD deficiency, 2 patients with glucose-6-phosphate isomerase deficiency and 1 case with hexokinase deficiency were found. Of 5 patients with stomatocytes on peripheral blood film, 3 had Mediterranean stomatocytosis/ macrothrombocytopenia (ABCG5/ABCG8) and 2 were found to have overhydrated hereditary stomatocytosis (RHAG).We also found 6 cases of HA to have a mutation in erythrocyte membrane protein-coding genes. Heterozygous nonsense mutation in the ANK1 gene was found in 2 cases and compound heterozygous missense mutations in ANK1 were seen in 1. Missense mutations were also found in SPTB gene in other 3 cases. Xerocytosis or dehydrated hereditary stomatocytosis (PEIZO1) was found in 3 patients.Seventeen cases for suspected CDA were studied and SEC23B mutations were present in 7. In one patient only heterozygous mutation was found. There could be the possibility of intronic mutation or long deletion/insertion in her. Notably, 6 patients with CDA showed mutations in PKLR (n=3), 1 each had mutations in MTRR, SPTB and PIEZO1 genes. We also found a mutation in GATA1 gene in a patient of CDA with thrombocytopenia.Conclusion(s)HA/CDA showed highly varied etiology. Our experience demonstrates the high diagnostic yield (>75%) of targeted resequencing for molecular diagnosis of unexplained anemias. It is cost effective and can expedite the diagnosis where conventional testing is not helpful. Timely detection of the etiology was helpful in genetic counseling. It not only offered therapeutic benefits to our patients but may help us in future antenatal diagnosis if required. Therapeutic implications include performing splenectomy which can ameliorate the anemia in selected subgroups of patients (HS, PK deficiency, CDA type II). DisclosuresNo relevant conflicts of interest to declare.

Hb Lepore-Leiden: A New δ/β Rearrangement Associated with a β-Thalassemia Minor Phenotype

The Lepore hemoglobins (Hbs) are a group of structural defects resulting from different recombination events between the δ- and β-globin genes. They may come with different β-thalassemia (β-thal) minor-like phenotypes in the carrier and with variably severe phenotypes in the rare homozygote, and in the common compound heterozygote with β-thal. The most seriously affected patients are those of Yugoslavian origin presenting with severe transfusion-dependent hemolytic anemia, dyserythropoiesis, hepatosplenomegaly and skeletal malformations. Because of genetic risk, couples where both partners are carriers of these combinations may require prognosis and prenatal diagnosis. In these cases, recognition of the defect must be done with particular care. We report a case of Hb Lepore induced by a yet unknown crossover event found in a 24-year-old Turkish male and compare the novel mutation with those previously reported.

Successful bone marrow transplantation in a child with red blood cell pyruvate kinase deficiency

We report the first successful use of BMT for the treatment of RBC pyruvate kinase (PK) deficiency in a boy who developed neonatal jaundice and severe transfusion-dependent hemolytic anemia a few months after birth. He received a BMT at the age of 5 from an HLA-identical sister who has normal PK activity after conditioning with busulfan and cyclophosphamide. The post-transplant course was uneventful. At present, 3 years after transplant, he is 8 years old and has a normal hemoglobin level and normal RBC PK activity without evidence of hemolysis. DNA analysis has confirmed full engraftment.

HB Yokohama [β31(B13)LEU→PRO] Detected AS A de novo Mutation in a Yugoslavian Boy

Hb Yokohama [beta 31 (B13)Leu----Pro] was observed in a young Yugoslavian boy as a de novo mutation. The child exhibited severe transfusion-dependent hemolytic anemia. The variant was detected and quantitiated at 10.5% by reversed phase high performance liquid chromatography. In vitro globin chain synthesis showed a slight imbalance with an alpha/beta ratio of 1.38. Structural characterization of the abnormal beta chain was done by high performance liquid chromatographic analysis, on material obtained by high salt precipitation. The mutation was confirmed by sequencing of the amplified DNA.

Prenatal diagnosis of hereditary elliptocytosis with molecular defect of spectrin.

Hereditary elliptocytosis (HE) is, in the heterozygous state, a common mild congenital hemolytic disease. In contrast, homozygous elliptocytosis is a severe transfusion-dependent hemolytic anemia. The major determinant of red cell membrane shape and stability is a two-dimensional proteinaceous meshwork named membrane skeleton. Spectrin, the most important protein of the membrane skeleton, is basically a heterodimer composed of alpha and beta chains. Within the membrane, spectrin dimers self-associate to form tetramers. In type I HE spectrin dimer self-association is defective and an excess of spectrin dimer is present in the patient's red cell membranes. The defective self-association is often correlated with an abnormality of the spectrin alpha chain which is depicted by limited tryptic digest of spectrin. In a family previously studied by us (Dhermy et al., 1984), the search for a spectrin defect in the red cells of the fetus of the pregnant mother was indicated for the following reasons: the diagnosis of heterozygous type I HE with the same spectrin variant had been made in the mother as well as in the father. Moreover, homozygous HE had been recognized in one of the children born two years previously with a persistent and severe transfusion dependent hemolytic anemia. Preliminary studies of normal fetal erythrocytes at twenty weeks gestation have shown that fetal and adult spectrin molecules are identical. The results obtained in the fetus at risk allowed us to diagnose type I HE (though elliptocytes were not present in the blood) for the following reasons: (i) erythrocyte deformability was decreased (ii) spectrin self-association was defective with an excess of dimer species in the membrane (iii) limited tryptic digest of spectrin showed the same abnormal pattern as seen in the heterozygous mother, with a decrease in the 80,000-dalton peptide and a concomitant increase in the 74,000-dalton peptide. The heterozygous state, strongly suspected on the tryptic digest pattern of fetal spectrin, was confirmed when the mother gave birth to a baby who did not have hemolytic anemia during the first 18 months of life.