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Blood Cells, Molecules & Diseases May 2018α-Thalassemia is an inherited, autosomal recessive, disorder characterized by a microcytic hypochromic anemia. It is one of the most common monogenic gene disorders in... (Review)
Review
α-Thalassemia is an inherited, autosomal recessive, disorder characterized by a microcytic hypochromic anemia. It is one of the most common monogenic gene disorders in the world population. The clinical severity varies from almost asymptomatic, to mild microcytic hypochromic, and to a lethal hemolytic condition, called Hb Bart's Hydrops Foetalis Syndrome. The molecular basis are usually deletions and less frequently, point mutations affecting the expression of one or more of the duplicated α-genes. The clinical variation and increase in disease severity is directly related to the decreased expression of one, two, three or four copies of the α-globin genes. Deletions and point mutations in the α-globin genes and their regulatory elements have been studied extensively in carriers and patients and these studies have given insight into the α-globin genes are regulated. By looking at naturally occurring deletions and point mutations, our knowledge of globin-gene regulation and expression will continue to increase and will lead to new targets of therapy.
Topics: Animals; Diagnosis, Differential; Disease Management; Genetic Association Studies; Genetic Counseling; Genetic Loci; Genotype; Humans; Mutation; Phenotype; alpha-Globins; alpha-Thalassemia
PubMed: 29032940
DOI: 10.1016/j.bcmd.2017.09.004 -
The New England Journal of Medicine Nov 2014More than 100 varieties of α-thalassemia have been identified. Their geographic distribution and the challenges associated with screening, diagnosis, and management... (Review)
Review
More than 100 varieties of α-thalassemia have been identified. Their geographic distribution and the challenges associated with screening, diagnosis, and management suggest that α-thalassemias should have a higher priority on global public health agendas.
Topics: Child; Geography, Medical; Humans; Prenatal Diagnosis; Quality-Adjusted Life Years; alpha-Thalassemia
PubMed: 25390741
DOI: 10.1056/NEJMra1404415 -
The New England Journal of Medicine Apr 2017
Review
Topics: Air Pollution; Anemia, Sickle Cell; Fetal Hemoglobin; Humans; Infant, Newborn; Infections; Phenotype; alpha-Thalassemia
PubMed: 28423290
DOI: 10.1056/NEJMra1510865 -
Hematology. American Society of... Dec 2021The thalassemias are inherited quantitative disorders of hemoglobin synthesis with a significant worldwide burden, which result in a wide spectrum of disease from the... (Review)
Review
The thalassemias are inherited quantitative disorders of hemoglobin synthesis with a significant worldwide burden, which result in a wide spectrum of disease from the most severe transfusion-dependent form to the mildest asymptomatic carrier state. In this article, we discuss the importance of carrier, prenatal, and newborn screening for thalassemia. We examine the rationale for who should be screened and when, as well as the current methodology for screening. Deficiencies in the newborn screening program are highlighted as well. With the advent of inexpensive and rapid genetic testing, this may be the most practical method of screening in the future, and we review the implications of population-based implementation of this strategy. Finally, a case-based overview of the approach for individuals with the trait as well as prospective parents who have a potential fetal risk of the disease is outlined.
Topics: Adult; Female; Genetic Testing; Humans; Infant; Infant, Newborn; Male; Prenatal Diagnosis; Young Adult; alpha-Thalassemia; beta-Thalassemia
PubMed: 34889395
DOI: 10.1182/hematology.2021000296 -
Hemolytic disease of the fetus and newborn: systematic literature review of the antenatal landscape.BMC Pregnancy and Childbirth Jan 2023Prevention of pregnancy-related alloimmunization and the management of hemolytic disease of the fetus and newborn (HDFN) has significantly improved over the past...
BACKGROUND
Prevention of pregnancy-related alloimmunization and the management of hemolytic disease of the fetus and newborn (HDFN) has significantly improved over the past decades. Considering improvements in HDFN care, the objectives of this systematic literature review were to assess the prenatal treatment landscape and outcomes of Rh(D)- and K-mediated HDFN in mothers and fetuses, to identify the burden of disease, to identify evidence gaps in the literature, and to provide recommendations for future research.
METHODS
We performed a systematic search on MEDLINE, EMBASE and clinicaltrials.gov. Observational studies, trials, modelling studies, systematic reviews of cohort studies, and case reports and series of women and/or their fetus with HDFN caused by Rhesus (Rh)D or Kell alloimmunization. Extracted data included prevalence; treatment patterns; clinical outcomes; treatment efficacy; and mortality.
RESULTS
We identified 2,541 articles. After excluding 2,482 articles and adding 1 article from screening systematic reviews, 60 articles were selected. Most abstracted data were from case reports and case series. Prevalence was 0.047% and 0.006% for Rh(D)- and K-mediated HDFN, respectively. Most commonly reported antenatal treatment was intrauterine transfusion (IUT; median frequency [interquartile range]: 13.0% [7.2-66.0]). Average gestational age at first IUT ranged between 25 and 27 weeks. weeks. This timing is early and carries risks, which were observed in outcomes associated with IUTs. The rate of hydrops fetalis among pregnancies with Rh(D)-mediated HDFN treated with IUT was 14.8% (range, 0-50%) and 39.2% in K-mediated HDFN. Overall mean ± SD fetal mortality rate that was found to be 19.8%±29.4% across 19 studies. Mean gestational age at birth ranged between 34 and 36 weeks.
CONCLUSION
These findings corroborate the rareness of HDFN and frequently needed intrauterine transfusion with inherent risks, and most births occur at a late preterm gestational age. We identified several evidence gaps providing opportunities for future studies.
Topics: Female; Humans; Pregnancy; Erythroblastosis, Fetal; Hydrops Fetalis; Hemolysis; Blood Transfusion, Intrauterine; Fetus
PubMed: 36611144
DOI: 10.1186/s12884-022-05329-z -
JAMA Network Open Oct 2023Sickle cell disease (SCD) is a monogenic disorder, yet clinical outcomes are influenced by additional genetic factors. Despite decades of research, the genetics of SCD... (Meta-Analysis)
Meta-Analysis
IMPORTANCE
Sickle cell disease (SCD) is a monogenic disorder, yet clinical outcomes are influenced by additional genetic factors. Despite decades of research, the genetics of SCD remain poorly understood.
OBJECTIVE
To assess all reported genetic modifiers of SCD, evaluate the design of associated studies, and provide guidelines for future analyses according to modern genetic study recommendations.
DATA SOURCES
PubMed, Web of Science, and Scopus were searched through May 16, 2023, identifying 5290 publications.
STUDY SELECTION
At least 2 reviewers identified 571 original, peer-reviewed English-language publications reporting genetic modifiers of human SCD phenotypes, wherein the outcome was not treatment response, and the comparison was not between SCD subtypes or including healthy controls.
DATA EXTRACTION AND SYNTHESIS
Data relevant to all genetic modifiers of SCD were extracted, evaluated, and presented following STREGA and PRISMA guidelines. Weighted z score meta-analyses and pathway analyses were conducted.
MAIN OUTCOMES AND MEASURES
Outcomes were aggregated into 25 categories, grouped as acute complications, chronic conditions, hematologic parameters or biomarkers, and general or mixed measures of SCD severity.
RESULTS
The 571 included studies reported on 29 670 unique individuals (50% ≤ 18 years of age) from 43 countries. Of the 17 757 extracted results (4890 significant) in 1552 genes, 3675 results met the study criteria for meta-analysis: reported phenotype and genotype, association size and direction, variability measure, sample size, and statistical test. Only 173 results for 62 associations could be cross-study combined. The remaining associations could not be aggregated because they were only reported once or methods (eg, study design, reporting practice) and genotype or phenotype definitions were insufficiently harmonized. Gene variants regulating fetal hemoglobin and α-thalassemia (important markers for SCD severity) were frequently identified: 19 single-nucleotide variants in BCL11A, HBS1L-MYB, and HBG2 were significantly associated with fetal hemoglobin (absolute value of Z = 4.00 to 20.66; P = 8.63 × 10-95 to 6.19 × 10-5), and α-thalassemia deletions were significantly associated with increased hemoglobin level and reduced risk of albuminuria, abnormal transcranial Doppler velocity, and stroke (absolute value of Z = 3.43 to 5.16; P = 2.42 × 10-7 to 6.00 × 10-4). However, other associations remain unconfirmed. Pathway analyses of significant genes highlighted the importance of cellular adhesion, inflammation, oxidative and toxic stress, and blood vessel regulation in SCD (23 of the top 25 Gene Ontology pathways involve these processes) and suggested future research areas.
CONCLUSIONS AND RELEVANCE
The findings of this comprehensive systematic review and meta-analysis of all published genetic modifiers of SCD indicated that implementation of standardized phenotypes, statistical methods, and reporting practices should accelerate discovery and validation of genetic modifiers and development of clinically actionable genetic profiles.
Topics: Humans; Fetal Hemoglobin; alpha-Thalassemia; Anemia, Sickle Cell; Genotype; Genetic Variation
PubMed: 37851445
DOI: 10.1001/jamanetworkopen.2023.37484 -
Blood Reviews Mar 2024α-Thalassemia is an inherited blood disorder characterized by decreased synthesis of α-globin chains that results in an imbalance of α and β globin and thus varying... (Review)
Review
α-Thalassemia is an inherited blood disorder characterized by decreased synthesis of α-globin chains that results in an imbalance of α and β globin and thus varying degrees of ineffective erythropoiesis, decreased red blood cell (RBC) survival, chronic hemolytic anemia, and subsequent comorbidities. Clinical presentation varies depending on the genotype, ranging from a silent or mild carrier state to severe, transfusion-dependent or lethal disease. Management of patients with α-thalassemia is primarily supportive, addressing either symptoms (eg, RBC transfusions for anemia), complications of the disease, or its transfusion-dependence (eg, chelation therapy for iron overload). Several novel therapies are also in development, including curative gene manipulation techniques and disease modifying agents that target ineffective erythropoiesis and chronic hemolytic anemia. This review of α-thalassemia and its various manifestations provides practical information for clinicians who practice beyond those regions where it is found with high frequency.
Topics: Humans; beta-Thalassemia; alpha-Thalassemia; Erythropoiesis; Hematologic Diseases; Erythrocyte Transfusion; Iron Overload
PubMed: 38182489
DOI: 10.1016/j.blre.2023.101165 -
The New England Journal of Medicine Oct 2020The cause of most fetal anomalies is not determined prenatally. Exome sequencing has transformed genetic diagnosis after birth, but its usefulness for prenatal diagnosis...
BACKGROUND
The cause of most fetal anomalies is not determined prenatally. Exome sequencing has transformed genetic diagnosis after birth, but its usefulness for prenatal diagnosis is still emerging. Nonimmune hydrops fetalis (NIHF), a fetal abnormality that is often lethal, has numerous genetic causes; the extent to which exome sequencing can aid in its diagnosis is unclear.
METHODS
We evaluated a series of 127 consecutive unexplained cases of NIHF that were defined by the presence of fetal ascites, pleural or pericardial effusions, skin edema, cystic hygroma, increased nuchal translucency, or a combination of these conditions. The primary outcome was the diagnostic yield of exome sequencing for detecting genetic variants that were classified as either pathogenic or likely pathogenic according to the criteria of the American College of Medical Genetics and Genomics. Secondary outcomes were the percentage of cases associated with specific genetic disorders and the proportion of variants that were inherited.
RESULTS
In 37 of the 127 cases (29%), we identified diagnostic genetic variants, including those for disorders affecting the RAS-MAPK cell-signaling pathway (known as RASopathies) (30% of the genetic diagnoses); inborn errors of metabolism and musculoskeletal disorders (11% each); lymphatic, neurodevelopmental, cardiovascular, and hematologic disorders (8% each); and others. Prognoses ranged from a relatively mild outcome to death during the perinatal period. Overall, 68% of the cases (25 of 37) with diagnostic variants were autosomal dominant (of which 12% were inherited and 88% were de novo), 27% (10 of 37) were autosomal recessive (of which 95% were inherited and 5% were de novo), 1 was inherited X-linked recessive, and 1 was of uncertain inheritance. We identified potentially diagnostic variants in an additional 12 cases.
CONCLUSIONS
In this large case series of 127 fetuses with unexplained NIHF, we identified a diagnostic genetic variant in approximately one third of the cases. (Funded by the UCSF Center for Maternal-Fetal Precision Medicine and others; ClinicalTrials.gov number, NCT03412760.).
Topics: Female; Genetic Variation; Humans; Hydrops Fetalis; Pregnancy; Prenatal Diagnosis; Prognosis; Exome Sequencing
PubMed: 33027564
DOI: 10.1056/NEJMoa2023643