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Carrier Screening For Inherited Genetic Conditions
Published in Vincenzo Berghella, Obstetric Evidence Based Guidelines, 2022
Whitney Bender, Lorraine Dugoff
Alpha-thalassemia results from a gene deletion of two or more copies of the four alpha-globin genes on chromosome 16. It is common among individuals of Southeast Asian, African, West Indian, and Mediterranean ancestry. Deletion of two genes, alpha-thalassemia trait, causes a mild hemolytic anemia. The deletions may occur on the same chromosome (cis aa/-) or on two different chromosomes (trans a-/a-). Individuals of Southeast Asian descent are more likely to carry the cis configuration compared to their African counterparts. Individuals with alpha-thalassemia trait are at increased risk for having a child with a more severe form of alpha-thalassemia. Hemoglobin H disease is caused by the deletion of three alpha-globin genes. Affected individuals have mild to moderate hemolytic anemia. Alpha-thalassemia major (Hb Bart disease) results from the absence of functional alpha-globin genes. Fetal hydrops and intrauterine fetal demise is the expected outcome in these cases due to the inability to produce functional HbF. Hemoglobin Bart disease does not usually occur in fetuses of alpha-thalassemia carriers of African origin, since individuals of African descent usually have the trans-configuration genotype. See Chap. 14 in Maternal-Fetal Medicine Evidence Based Guidelines.
Habitual Abortion
Published in E. Nigel Harris, Thomas Exner, Graham R. V. Hughes, Ronald A. Asherson, Phospholipid-Binding Antibodies, 2020
Dwight D. Pridham, Christine L. Cook
Although anemia is a frequent complication of pregnancy (more than half of all gestations), it rarely is associated with fetal wastage. Iron deficient states and B12 deficiencies are not associated with SAB.69 There is some evidence70 that folate deficiency is associated with a higher rate of SAB and HAB. Most of the inherited hemoglobinopathies are benign during pregnancy. These include Methemoglobin (HbM Boston), increased oxygen affinity (Hb Chesapeake), unstable hemoglobin (Hb Saki), and beta-thalassemia (Hb B Thai).69 Alpha-thalassemia is associated with a slightly increased rate of SAB, particularly in Southeast Asian patients. The alpha-thalassemia-2 genotype contains a defect in one of the two loci for alpha globulin on one chromosome. This is the common genotype in the Mediterranean population. Heterozygosity yields a silent carrier state and no anemia. Homozygosity produces alpha-thalassemia. In Southeast Asians, alpha-thalassemia-1 genotype is more common; this is a defect in both loci for alpha-globulin on one chromosome. In this condition, heterozygosity causes alpha-thalassemia, whereas homozygosity, with no normal allele for alpha-globulin results in lethal hydrops fetalis.71
The HbS Containing Cell
Published in Ronald L. Nagel, Genetically Abnormal Red Cells, 2019
Ronald L. Nagel, Mary E. Fabry
Effect of alpha- and beta-thalassemia — Four genes control the production of alpha globin chains; a single deletion results in alpha thalassemia trait (-α/αα) which has no clinical or hematological manifestations in A A individuals. Alpha thalassemia is more prevalent in black populations103 and is even more prevalent among patients with sickle cell anemia because these patients have prolonged survival.104 The presence of alpha thalassemia (-α/αα) reduced the percent of dense cells in a population of New York City black patients from 24 ± 15% for nonthalassemic individuals to 12 ± 8%.105 Embury et al.106 found a reduction from about 29% of the cells with a density greater than 1.1056 g/mℓ for patients with all four alpha genes to about 13% of the cells for patients with alpha thalassemia. These results confirm earlier studies that reported fewer ISCs107 for patients with two alpha gene deletions (-α/-α) and a successively lower MCHC for each alpha gene deletion. From the data of both Embury et al. and Fabry et al.105,106 it can be seen that the latter result is due to the reduced percent of dense cells which results in a reduced average MCHC rather than a reduction in the density of the discocyte population such as that seen in alpha and beta thalassemia in A A individuals.
Whole exome sequencing and rare variant association study to identify genetic modifiers, KLF1 mutations, and a novel double mutation in Thai patients with hemoglobin E/beta-thalassemia
Published in Hematology, 2023
Chattree Hantaweepant, Bhoom Suktitipat, Manop Pithukpakorn, Yingyong Chinthammitr, Chanin Limwongse, Nawaporn Tansiri, Surasak Sawatnatee, Chayamon Takpradit, Wannaphorn Rotchanapanya, Saranya Pongudom, Kanyaporn Charoenprasert, Kittiphong Paiboonsukwong, Wichuda Thamprasert, Narumol Nolwachai, Wanlapa Rattanasawat, Busakorn Sae-Aeng, Nisachon Khorwanichakij, Putchong Saetow, Supawee Saengboon, Krittichat Kamjornpreecha, Wikanda Pholmoo, Boonyanuch Dujjawan, Noppadol Siritanaratkul
Most types of beta-thalassemia are inherited by autosomal recessive pattern including homozygote or compound heterozygote. However, patients who carried the same beta genotype do not express the same phenotype. There are other genetic modifiers affected clinical severity [2]. In this study, number of patients who carried β0/βE or β0/β0 was comparable in both the mild and severe groups (76.9% vs 83.6%). Previous studies using the same scoring system to classify phenotypes of Thai patients with Hb E/beta-thalassemia similarly reported a higher proportion of β0 mutations in both the mild and severe groups (76.1% vs 84.5% by Sripichai et al. [10] and 91.9% vs 100% by Nuinoon et al. [7]). Both studies tested alpha mutations by PCR. They found that around one-quarter of the mild patients carried alpha-thalassemia heterozygote that can alleviate beta-thalassemia severity. Our study used WES, so deletional alpha mutations, which are more prevalent than point mutations, could not be revealed. However, due to quite similar patients’ samples, if the minority of our mild patients carried alpha-thalassemia heterozygote and/or β+ mutations, we still cannot explain the observed majority with mild phenotype.
Prevalence of Hemoglobinopathies in Premarital Screening in the Province of Nigde, Turkey
Published in Hemoglobin, 2023
Gonul Seyda Seydel, Durmus Ayan, Tevfik Balci, Muhammet Bayraktar, Inayet Gunturk
Alpha thalassemia is caused by α-globin gene mutations that cause absent or decreased the production of α-globin chains. İt occur in nearly all populations and affect up to 5% of the world’s population. The geographic distribution of α-thalassemia has significantly changed as a result of immigration patterns [1,39]. Iron deficiency anemia is another common hematological problem that is also a public health issue in many developing countries [40]. In this study, 183 individuals (9.1%) were considered as possibly having an iron deficiency, α-thalassemia, or silent β-thalassemia carrier, and 20 of them were migrants, including 10 from Syria, two from Somalia, two from Iraq, one from Iran, one from Afghanistan, one from Turkmenistan, one from Kazakhstan, one from Ukraine, and one from Romania. Since iron deficiency is the most prevalent cause of hypochromic microcytic anemia, it is essential to measure iron parameters to distinguish between iron deficiency anemia and thalassemia. It was interesting to note that among Turks 8.37% had reduced MCV/MCH and normal HbA2, while among immigrants it was 29.9%. Many may have iron deficiency rather than hemoglobinopathies. It might be because of the iron deficiency among immigrants, due to expected socioeconomic constraints relevant to their situation.
Sickle cell disease in gulf cooperation council countries: a systematic review
Published in Expert Review of Hematology, 2022
Amani Abu-Shaheen, Doaa Dahan, Humariya Henaa, Abdullah Nofal, Doaa A. Abdelmoety, Muhammad Riaz, Mohammed AlSheef, Abdulrahman Almatary, Isamme AlFayyad
HbF is linked to the haplotype and has been linked to the clinical course of SCD. High HbF levels were linked to fewer clinical manifestations of SCD and a lower occurrence of organ damage. According to our findings, the majority of SCD patients have an elevated HbF of more than 10%. It has been reported in the United States that coinheritance with the alpha-thalassemia gene has little influence on acute events during childhood [38,42,43]. Brazilian studies discovered a link between SCD clinical manifestations and HbF [134–138]. Furthermore, the findings of our study revealed that many studies documented the existence of alpha thalassemia and its trait. While no correlations have been found between coinheritance with alpha-thalassemia and clinical symptoms [139–141], it may be associated with fewer infections or repeated acute pain crises [142,143].