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Basic genetics and patterns of inheritance
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Turner syndrome is one of the most familiar sex chromosome abnormalities. It is caused by the presence of only one X chromosome (45,X) in phenotypic females. This classic Turner karyotype is seen in 50% of cases; other cases may be mosaic (45,X/46,XX), or may be caused by an abnormal X chromosome, such as an isochromosome or ring X (1). There may be portions of a Y chromosome present or mosaicism for a 46,XY cell line in some cases. FISH testing for SRY is recommended for detection of Y chromosome material. Turner syndrome is seen in about 1 in 2500 newborn girls. However, it is well known that the incidence is much higher in early pregnancy, with more than 98% of 45,X embryos and fetuses being lost by spontaneous miscarriage. This would suggest that the incidence among conceptuses could be as high as 1.5%, an extraordinarily high frequency (5).
Causes and risk factors
Published in Janetta Bensouilah, Pregnancy Loss, 2021
In 0.3% of cases of spontaneous miscarriage and 3–5% of cases of recurrent miscarriage the cause is parental translocation.8–10 This condition affects one or more rarely both parents, and occurs when a piece of one chromosome breaks off and attaches to another chromosome. In a balanced translocation there is no loss or gain of important genetic material and the person is asymptomatic. However, when they produce eggs or sperm and the cells divide, they only receive half the parental chromosomes. When the individual tries to have children, if fertilisation occurs with one of the abnormal eggs or sperm the embryo will inherit the translocation and either will be a balanced carrier and compatible with normal life, or will be unbalanced and either miscarry or produce abnormalities. Both males and females can be carriers of translocations. There is some evidence that paternal translocations may have less impact on reproductive outcome than those carried by women.2 Even if a couple have had a healthy child, followed by subsequent miscarriages, it is possible that the baby inherited the balanced translocation and therefore survived, but the miscarried babies were chromosomally abnormal. Generally the outlook is positive for balanced translocations, eventually resulting in healthy offspring, and parents with identifiable chromosomal abnormalities should be referred to genetic counsellors for guidance.
Pediatric Oncology
Published in Pat Price, Karol Sikora, Treatment of Cancer, 2020
Stephen Lowis, Rachel Cox, John Moppett, Helen Rees
Children with certain congenital chromosomal abnormalities, or abnormalities of DNA repair or immune regulation, have a notably higher risk of developing ALL—for example Down syndrome, Fanconi anemia, and Wiskott–Aldrich syndrome. There is an increasing recognition of the role of underlying predisposition syndromes and single nucleotide polymorphisms in the etiology of ALL.
Prenatal chromosomal microarray analysis in foetuses with isolated absent or hypoplastic nasal bone
Published in Annals of Medicine, 2022
Xiaomei Shi, Jian Lu, Ling Li, Ran Wei, Jing Wu
Previous studies have demonstrated that the absence or hypoplasia of NB may be one of the strongest ultrasound markers for Down syndrome and other chromosomal abnormalities in both the first and second trimesters. However, studies of foetuses with isolated absent or hypoplastic NB by CMA were limited. We specifically focussed on CMA as first-tier testing in foetuses with isolated absent or hypoplastic NB and attempted to elaborate the relationship between pathogenic CNVs and isolated absent or hypoplastic NB. We identified chromosomal abnormalities in 9.0% foetuses, including 13 aneuploidies and 7 pathogenic CNVs. Down syndrome was the most common chromosomal abnormalities in our study and detected in 10 (4.5%) foetuses. This result further supports the idea that absent or hypoplastic foetal NB is a strong marker for Down syndrome.
Reproductive outcomes of infertile couples undergoing assisted reproductive technology who are carriers of chromosomal abnormalities: a retrospective cohort study
Published in Annals of Medicine, 2022
Ling Cui, Fang Wang, Yonghong Lin, Min Li
However, few studies have examined whether couples who were carriers of chromosomal abnormalities undergoing assisted reproductive technology (ART) have a significantly different pregnancy rate and number of embryo transfer procedures performed. Preimplantation genetic technologies (PGTs) [7] are increasingly being used with in vitro fertilization (IVF). Genetic counselling and discussion of possible preimplantation genetic testing should be offered when a structural rearrangement (translocation, inversion, deletion, and insertion) is discovered in a parent. PGT is now able to differentiate inherited chromosome arrangements. Chromosomal testing is a routine screening test for infertile couples who have an indication for ART. For all carriers of chromosomal abnormalities, we provide genetic counselling. Some studies found out carriers of chromosomal abnormalities still having a chance of having normal children [8,9]. Even couples with unbalanced chromosomal abnormalities had a similar chance to have a healthy child as non-carrier couples, despite a higher risk of miscarriage [10].
Self-reported effects of perceived social support on marital quality in balanced translocation patients and their spouses undergoing preimplantation genetic testing in China: actor–partner interdependence model
Published in Journal of Obstetrics and Gynaecology, 2022
Fengyi Mo, Xiaorui Hu, Qing Ma, Li Zhang, Lanfeng Xing
Chromosomal abnormalities, one of the most frequent causes of genetic diseases (Mierla et al. 2015), are defined as a genetic disease caused by abnormalities in the number, morphology or structure of chromosomes, often resulting in miscarriage, congenital mental retardation, mental retardation and multiple malformations (Chen et al. 2020). The most frequent chromosomal abnormalities are balanced chromosomal rearrangement, sex chromosomal mosaicism and inversion. The rate of a chromosomal anomaly in the general population is 0.37–1.86%; however, the rate in patients with a history of adverse pregnancy is 3.95–14.3% (Liu et al. 2013). Chromosomal abnormalities cannot be treated medically since they are irreversible (Chen et al. 2020). Balanced translocation is a situation in which both breakage and reconnection of chromosomes occur at abnormal positions, including both Robertsonian and reciprocal translocations. Approximately, 0.5–5% of couples with reproductive problems carry a balanced translocation (Munné et al. 2000; Findikli et al. 2003). However, at present, the specific mechanisms underlying balanced translocation remain unclear (Chen et al. 2020).