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Carrier Screening For Inherited Genetic Conditions
Published in Vincenzo Berghella, Obstetric Evidence Based Guidelines, 2022
Whitney Bender, Lorraine Dugoff
Hemoglobinopathies are a diverse group of inherited single-gene disorders that result from variations in the structure and/or function of hemoglobin. The most common hemoglobinopathies—sickle cell disease, beta-thalassemia, and alpha-thalassemia—are all autosomal recessive conditions. A brief discussion of each of these disorders is included next. ACOG recommends carrier screening for individuals of African, Southeast Asian, and Mediterranean ancestry. Figure 6.1 outlines a screening strategy [22]. A complete blood count (CBC) in combination with a hemoglobin electrophoresis is recommended for screening individuals of African ancestry. A CBC with red cell indices is the initial recommended screening test for individuals of Southeast Asian and Mediterranean ancestry. Individuals with a low mean corpuscular volume (MCV) and normal iron status should have a hemoglobin electrophoresis. Southeast Asians with a normal hemoglobin electrophoresis should have molecular testing to rule out alpha-globin gene deletions characteristic of alpha-thalassemia. Couples determined to be at increased risk for having a child with sickle cell disease or thalassemia should be referred to a genetic counselor [24]. For additional information regarding hemoglobinopathies, refer to Chaps. 14 and 15 in Maternal-Fetal Medicine Evidence Based Guidelines.
Maternal Anemia
Published in Vincenzo Berghella, Maternal-Fetal Evidence Based Guidelines, 2022
Ashley E. Benson, Marcela C. Smid
See Tables 14.1–14.3 for types of hemoglobins. Tables 14.4 and 14.5 describe the types of hemoglobinopathies and their clinical significance. Cis-α-thalassemia is common among women in Southeast Asian ancestry; β-thalassemia is common among women of Mediterranean, Asian, Middle Eastern, Hispanic, and West Indian ancestry. However, self-identified ethnicity is not a good predictor of risk as ethnic background may be assumed or not known [2].
Haematological disorders
Published in Judy Bothamley, Maureen Boyle, Medical Conditions Affecting Pregnancy and Childbirth, 2020
Haemoglobinopathies is a broad term used to describe a range of disorders that affect the structure of haemoglobin, an essential component of RBCs. These include: ◗ Sickle cell disease (SCD)◗ Alpha thalassaemia◗ Beta thalassaemia Sickle cell disease is due to changes to the structure and quality of the haemoglobin and in thalassaemia the amount of haemoglobin that the body produces is reduced which affects oxygen carrying capacity. In the past, pregnancy put women with SCD and thalassaemia major at extreme risk; in fact, those with thalassaemia major rarely survived to child-bearing age; but new technology and advances in identification and care have led to much improved outcomes for both mothers and babies, and many women with haemoglobinopathies are now more likely to contemplate pregnancy.
Hematological and molecular characteristics of a novel α-globin variant Hb Liangqing (HBA2:c.224A>G)
Published in Hematology, 2023
Youqiong Li, Shulin Liang, Liang Liang, Lihong Zheng, Xiaocai Lu
Hemoglobinopathies are the most common inherited single-gene disorders in southern China, including thalassemias and hemoglobin (Hb) variants [1–3]. The molecular basis involves deletions, point mutations, and gene fusions [4,5]. During hematopoiesis, these alterations can form abnormal Hb variants or reduce globin chain synthesis in erythroid cells. The decrease or absence of globin chains leads to excess unpaired globin chains that precipitate in the erythrocytes, resulting in increased erythrocyte destruction or ineffective erythropoiesis [6]. Due to its functional role and genetic complexity, hemoglobinopathies seriously affect human health, and patients with the disease have high morbidity and mortality [7]. The clinical phenotype of hemoglobinopathies is determined by genotype. The phenotype can range from asymptomatic carrier status to mild, moderate, or severe anemia, which may be fatal [8]. Therefore, accurate diagnosis of hemoglobinopathies is very important in these high-incidence regions. In many provinces of southern China, it has become a government policy to carry out hemoglobinopathy screening before marriage, pregnancy, and childbirth.
A Case of Misdiagnosis Caused by the Coinheritance of Hb G-Siriraj [β7(A4)Glu→Lys; HBB: c.22G>A] and Hb H Disease
Published in Hemoglobin, 2022
Zhi-Yang Guan, Ze-Yan Zhong, Zhi-Bang Xu, Jian-Hong Chen, Yan-Hui Liu
Hemoglobinopathies are a group of inherited hemoglobin (Hb) disorders caused by abnormal Hb structure or insufficient synthetic amount of Hb. They can be divided into two general types: the Hb variants and the thalassemias, or a combination of the two. They are both caused by defects in the globin genes; the former leads to an abnormal molecular structure of globin chain, while the latter leads to insufficiency or inability to synthesize the globin chain [1]. To date, a recent query of the human Hb variant (HbVar) (http://globin.cse.psu.edu) database [2], showed that more than 1800 Hb variants have now been found worldwide. Despite the fact that most of these variants are clinically and hematologically silent, they can interact with thalassemias, which could sometimes give rise to complicated routine thalassemia diagnostics [3]. Hb G-Siriraj [β7(A4)Glu→Lys; HBB: c.22G>A], was first reported by Tuchinda et al. [4] in 1965. Hb G-Siriraj alone is a benign condition, but its coexistence with thalassemia may have a clinical significance. Hb H disease is the severest form of α-thalassemia (α-thal) compatible with postnatal life, and the affected individual would have only one functional α-globin gene [5]. To date, a case of Hb G-Siriraj in combination with thalassemia has not been reported in the literature. Herein, we report a case of misdiagnosis caused by the coinheritance of Hb G-Siriraj and Hb H disease.
Thalassemia in Asia 2021 Thalassemia in Brunei Darussalam
Published in Hemoglobin, 2022
Seow-Chin Chong, Sofian Metassan, Noorainun Yusof, Roserahayu Idros, Norehan Johari, Ihsan N. Zulkipli, Hazim Ghani, Mei-Ann Lim, Surita Taib, Zen-Huat Lu, Mas R.W. Abdul-Hamid
Hemoglobinopathies are a diverse group of inherited blood disorders characterized by decreased expression of the functional hemoglobin (Hb) proteins. The disorder results from hereditary mutations that cause qualitative defects leading to structurally abnormal Hb variants such as Hb S (HBB: c.20A>T), Hb E (HBB: c.79G>A) and Hb Constant Spring (Hb CS or HBA2: 427 T>C) or quantitative defects of the globin expression as in thalassemia disorders. Thalassemia is the most common type of hemoglobinopathy. Additionally, there are also cases where Hb variants can be associated with thalassemia genotypes and may cause clinical complications [1]. The thalassemia types vary depending on which polypeptide chains’ expressions are affected. The globin chains are coded by the α gene clusters (HBA1/HBA2) on chromosome 16 and the β-globin gene cluster (HBB) on chromosome 11 [2]. Decreased globin chain expressions can be caused by deletion of structural genes, or mutations that cause decreased RNA or protein synthesis or stability [3]. Where there is an imbalance of α and β chains, there is a formation of unstable tetramers and an accumulation and precipitation of unpaired chains that is followed by hemolysis, and ineffective erythropoiesis [4]. Most thalassemia cases are inherited in an autosomal recessive manner, and thus, family history is effectively part of the primary line of establishing a diagnosis.