First Report of a Novel Deletion Due toεγδβ-Thalassemia in a Chinese Family

Case Report: Clinical and Hematological Characteristics of εγδβ Thalassemia in an Italian Patient

INTRODUCTION

εγδβ thalassemia is a rare form of β-thalassemia mostly described in children originating from Northern Europe. Only anecdotic cases from the Mediterranean area are reported. The diagnosis is challenging, considering the rarity of the disease and its heterogeneous clinical presentation. Most patients have neonatal microcytic anemia, sometimes requiring in utero and/or neonatal transfusions, and typically improving with age.

CASE DESCRIPTION

We report on an Italian newborn presenting with severe neonatal anemia that required red blood cell transfusion. After the first months of life, hemoglobin levels improved with residual very low mean corpuscular volume. β and α thalassemia, IRIDA syndrome, and sideroblastic anemia were excluded. Finally, a diagnosis of εγδβ thalassemia was made after microarray analysis of single nucleotide polymorphisms revealed a 26 kb single copy loss of chromosome 11p15.4, including the HBD, HBBP1, HBG1, and HBB genes.

CONCLUSIONS

Despite its rarity, the diagnosis of εγδβ thalassemia should be considered in newborns with severe neonatal anemia requiring in utero and/or neonatal transfusions, but also in older infants with microcytic anemia, after excluding more prevalent red blood cell disorders.

Thalassemias: From gene to therapy

Thalassemias (α, β, γ, δ, δβ, and εγδβ) are the most common genetic disorders worldwide and constitute a heterogeneous group of hereditary diseases characterized by the deficient synthesis of one or more hemoglobin (Hb) chain(s). This leads to the accumulation of unstable non-thalassemic Hb chains, which precipitate and cause intramedullary destruction of erythroid precursors and premature lysis of red blood cells (RBC) in the peripheral blood. Non-thalassemic Hbs display high oxygen affinity and no cooperativity. Thalassemias result from many different genetic and molecular defects leading to either severe or clinically silent hematologic phenotypes. Thalassemias α and β are particularly diffused in the regions spanning from the Mediterranean basin through the Middle East, Indian subcontinent, Burma, Southeast Asia, Melanesia, and the Pacific Islands, whereas δβ-thalassemia is prevalent in some Mediterranean regions including Italy, Greece, and Turkey. Although in the world thalassemia and malaria areas overlap apparently, the RBC protection against malaria parasites is openly debated. Here, we provide an overview of the historical, geographic, genetic, structural, and molecular pathophysiological aspects of thalassemias. Moreover, attention has been paid to molecular and epigenetic pathways regulating globin gene expression and globin switching. Challenges of conventional standard treatments, including RBC transfusions and iron chelation therapy, splenectomy and hematopoietic stem cell transplantation from normal donors are reported. Finally, the progress made by rapidly evolving fields of gene therapy and gene editing strategies, already in pre-clinical and clinical evaluation, and future challenges as novel curative treatments for thalassemia are discussed.

A Novel εγδβ-Thalassemia Deletion Associated with Severe Anemia at Birth and a β-Thalassemia Intermedia Phenotype Later in Life in Three Generations of a Greek Family

We describe a novel deletion causing heterozygous εγδβ-thalassemia (εγδβ-thal) across three generations of a Greek family. The Greek deletion is about 72 kb in length, spanning from the hypersensitive site 4 (HS4) in the locus control region (LCR) to the 3' end of the β-globin gene, thus encompassing the entire β-globin gene cluster. The deletion caused severe but transient neonatal anemia and a non transfusion-dependent chronic hemolytic anemia state later in life, resembling mild β-thalassemia intermedia (β-TI) rather than β-thalassemia (β-thal) trait, as had been previously reported. Apart from the presentation of clinical and laboratory characteristics, the challenges involving clinical management are also discussed.

Clinical and molecular characterization of novel deletions causing epsilon gamma delta beta thalassemia: Report of two cases

Epsilon gamma delta beta (εγδβ)⁰ - thalassemia is a very rare disorder that results from large deletions in the β-globin gene cluster which abolish all regional globin chain gene expression from that allele. Since it is an exceedingly rare cause of neonatal anemia and is not detected by routine newborn screening, it is usually not suspected clinically and commonly undiagnosed or misdiagnosed. In this study, we describe two patients diagnosed in our hospital with (εγδβ)⁰-thalassemia based on the results obtained from DNA microarray analysis of their peripheral blood. The first patient of mixed European descent presented as a neonate with microcytic hemolytic anemia, hyperbilirubinemia, hypoglycemia and hypothermia, and was found to have a 2.2 Mb loss that included the entire β-globin gene cluster and the locus control region (LCR). The second patient, also of mixed European descent, presented in the neonatal period with anemia, thrombocytopenia and cutaneous extramedullary hematopoiesis, and was found to have a 59 kb loss that included the β-globin LCR, HBE1, HBG1, and HBG2 genes. Both cases highlight the importance of recognizing the clinical features of (εγδβ)⁰-thalassemia and implementing appropriate testing to clarify the diagnosis and manage the condition.

A novel 223 kb deletion in the beta-globin gene cluster was identified in a Chinese thalassemia major patient

INTRODUCTION

Although mutations in the human beta-globin gene cluster are essentially point mutations, several large deletions have been described in recent years.

METHODS

We have identified a novel 223 kb deletion in a Chinese patient by multiplex ligation-dependent probe amplification and characterized it by next-generation sequencing, Gap-PCR, and DNA sequence analysis.

RESULTS

The deletion extends from the 3'UTR of the δ globin gene (HBD) to 215 kb downstream of the HBB. Compound heterozygous with the typical β-thalassemia-CD41-42(-CTTT) mutation, the proband presented with microcytosis and hypochromic red cells, and required regulate transfusion. The patient was clinically diagnosed with thalassemia major.

CONCLUSION

Our study widens the mutation spectrum of β-thalassemia. In addition, this case may spark future studies of the regulatory regions of the beta-globin gene cluster.

Experience of chromosomal microarray applied in prenatal and postnatal settings in Hong Kong

Chromosomal microarray (CMA) is recommended as a first tier investigation for patients with developmental delay (DD), intellectual disability (ID), autistic spectrum disorder (ASD), and multiple congenital anomalies (MCA). It is widely used in the prenatal and postnatal settings for detection of chromosomal aberrations. This is a retrospective review of all array comparative genomic hybridization (aCGH/ array CGH) findings ascertained in two major prenatal and postnatal genetic diagnostic centers in Hong Kong from June 2012 to December 2017. Medical records were reviewed for cases with pathogenic and variants of uncertain clinical significance (VUS). Classification of copy number variants (CNVs) was based on current knowledge and experience by August 2018. The aims of this review are to study the diagnostic yield of array CGH application in prenatal and postnatal settings in Hong Kong and to describe the spectrum of abnormalities found. Prenatal indications included abnormal ultrasound findings, positive Down syndrome screening, abnormal noninvasive prenatal test results, advanced maternal age and family history of chromosomal or genetic abnormalities. Postnatal indications included unexplained DD, ID, ASD, and MCA. A total of 1,261 prenatal subjects and 3,096 postnatal patients were reviewed. The prenatal diagnostic yield of pathogenic CNV and VUS (excluding those detectable by karyotype) was 3.5%. The postnatal diagnostic yield of pathogenic CNV was 15.2%. The detection rates for well-defined microdeletion and microduplication syndromes were 4.6% in prenatal and 6.1% (1 in 16 index patients) in postnatal cases, respectively. Chromosomes 15, 16, and 22 accounted for over 21 and 25% of pathogenic CNVs detected in prenatal and postnatal cohorts, respectively. This review provides the first large scale overview of genomic imbalance of mostly Chinese patients in prenatal and postnatal settings.