Radiation Hormesis in Reproduction
T. D. Luckey in Radiation Hormesis, 2020
The chromosomal abnormality of Down’s syndrome is sometimes associated with low doses of ionizing radiation. A direct connection with ionizing radiation would present a complicated and most unusual chromosomal activity since 95% of the cases are due to trisomy of chromosome 21. Trisomy is the presence of three members of a chromosome which would normally occur in pairs. Trisomy usually occurs in older mothers’ young. No excess abnormalities or Down’s syndrome have been found following the Chernobyl contaminated air in Austria.4 Questionable evaluation of controls and the inadequacy of statistics involving such low numbers make these observations dubious.58 The extensive data from Japanese bomb survivors show no statistically significant increase in chromosomal aberrations.435 The incidence of Down’s syndrome and other viable malformations showed no correlation with background radiation in Japan from 1978 to 1981.931 These results suggest that background radiation is not a predominant factor in congenital abnormalities.
Genetics
Manoj Ramachandran, Tom Nunn in Basic Orthopaedic Sciences, 2018
In trisomy, the cells have an extra chromosome. The most common trisomy compatible with life is trisomy 21, or Down’s syndrome. The incidence of trisomy 21 is around 1 in 660 live births, with an increased risk in mothers over the age of 35 years. The aetiology in 94% of cases is the failure of separation of the autosomal pair during meiosis. This produces a gamete with two homologous chromosomes, which, when joined with a normal gamete during fertilization, produces trisomy. In 3.5% of case, chromosomal rearrangement occurs following translocation of one of the autosomes. The remaining 2.5% of cases occur due to mosaicism, ain which some of the body cells have a normal complement of 46 chromosomes but others have 47 chromosomes. Mosaicism occurs following defects in mitosis during formation of the zygote.
Counseling Prenatal Diagnosis Patients
Regina Furlong Lind, Debra Honig Bachman in Fundamentals of Perinatal Social Work, 2012
Karyotype abnormalities, also called aneuploidies, are abnormalities of chromosome number or shape. They form three basic groups: trisomies, monosomies, and chromosomal rearrangements. Normally, the cells in human tissues have 46 chromosomes: 2 of each of 22 somatic chromosomes and 2 sex chromosomes. If the egg or sperm cell which gives rise to an embryo has an extra copy of a chromosome, this leads to a trisomy. Trisomies are always associated with mental retardation. Trisomy 21 or Down syndrome is the most common trisomy. It occurs when there are 3 copies of chromosome 21. Most other trisomies are lethal and lead to miscarriage during the pregnancy. Some other trisomies (trisomies for chromosomes 13, 15 or 18) can lead to the birth of a live child who may also have visible structural defects and who usually dies within hours or weeks of birth. Monosomy occurs when only one copy of a certain chromosome is present. Monosomies are all lethal except for the monosomy of the sex chromosome where only one X is present. This karyotype is known as Turner’s syndrome. Turner’s is a very common cause of miscarriage, but some of these fetuses can survive to have only minor birth defects. Trisomies and monosomies occur more commonly as maternal age rises. They are not hereditary.
Co-occurrence of incontinentia pigmenti and down syndrome: examining patients’ potential susceptibility to autoimmune disease, autoinflammatory disease, cancer, and significant ocular disease
Published in Ophthalmic Genetics, 2021
David C. Gibson, Natario L. Couser, Kayla B. King
Down syndrome is a common genetic condition that occurs at an incidence of about one case in every 700 births. Most commonly, it is caused by a nondisjunction event resulting in the presence of three copies of chromosome 21, otherwise known as trisomy 21. A minority of cases are caused by a Robertsonian translocation which results in the presence of extra material from chromosome 21 attached to another chromosome. Down syndrome classically presents with characteristic physical and facial features, in addition to developmental and intellectual delays. Like patients with Noonan syndrome, individuals with Down syndrome have an increased risk of developing autoimmune and autoinflammatory diseases, like hypothyroidism, type 1 DM, celiac disease, and arthropathy of Down syndrome. Individuals with Down syndrome also have a predisposition to certain cancers, like acute myelocytic leukemia (AML), acute lymphocytic leukemia (ALL), and testicular malignancy. The susceptibility to immune-related disorders and certain cancers seen in patients with Down syndrome is thought to be due to interferon hyperactivity and disorganized T cell and B cell responses.
Early Pregnancy Losses: Review of Nomenclature, Histopathology, and Possible Etiologies
Published in Fetal and Pediatric Pathology, 2018
M. Halit Pinar, Karen Gibbins, Mai He, Stefan Kostadinov, Robert Silver
Among chromosomal abnormalities in early pregnancy losses, 86%–91% are numerical chromosomal abnormalities, which can be subdivided into aneuploidy (trisomies and monosomies) and polyploidy. Increasing maternal age increases risk for aneuploidy and, indeed, increases the risk for miscarriage. Risk of early pregnancy loss ranges from 8.9% in women ages 21–25 years to 74.7% in women older than 45 years (45). Trisomies are the most frequently occurring numerical chromosomal abnormalities (52%–63%), followed by polyploidy (17%–21%) and monosomy X (11%–13%) (8,46). Most trisomies occur as a consequence of nondisjunction during maternal meiosis I. Trisomy 16 is the most common trisomy in pregnancy loss specimens, followed by trisomies of 22, 15, and 21 (9). Monosomy X is also common and usually occurs as a result of paternal sex chromosome loss. Autosomal monosomies are less common than monosomy X (2).
Prenatal management of choroid plexus cyst in a developing country: case report
Published in Journal of Obstetrics and Gynaecology, 2020
Olufemi Adebari Oloyede
A 39-year-old patient, gravida 3, para 2+0, was referred to the unit for genetic counselling and further evaluation of the index pregnancy. Her last child had been diagnosed with Down syndrome and VSD, which was successfully operated after delivery. The patient’s routine anomaly ultrasound scan, which was carried out at 20 weeks of gestation, revealed a unilateral CPC that is approximately 5.8 mm in diameter (Figure 1). The follow-up detailed anatomy scan did not reveal any other soft markers for aneuploidy or structural abnormality in the foetus. She was counselled to carry out a maternal serum triple screening test and the assay results were within the normal ranges. She was counselled to have invasive testing and the chorionic villous sample that was obtained was used for molecular analysis by quantitative fluorescent polymerase chain reaction (QF-PCR). Trisomy 21 was diagnosed. The woman was offered non-direction post-screening counselling, during which the nature of the foetal diagnosis and the prognosis were discussed. Following this, she opted for a voluntary termination of the pregnancy.
Related Knowledge Centers
- Chromosome 21
- Down Syndrome
- Trisomy 16
- Miscarriage
- Meiosis
- NONdisjunction
- Aneuploidy
- Chromosome
- Polysomy
- Mosaic