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Chromosome abnormalities
Published in Angus Clarke, Alex Murray, Julian Sampson, Harper's Practical Genetic Counselling, 2019
A chromosomal mosaic is an individual whose organs contain more than one chromosomally distinct line of cells. When one of the cell lines is normal (e.g. 45,X/46,XX Turner mosaicism), the phenotype of the individual will usually be intermediate between the full disorder and normal. Some chromosome disorders are only known in mosaic form (e.g. mosaic trisomy 8, and mosaic 12p tetrasomy or Pallister-Killian syndrome), the full condition probably being lethal.
Understanding genetics and genetic tests
Published in David M. Luesley, Mark D. Kilby, Obstetrics & Gynaecology, 2016
A well-known mosaic condition is the Pallister-Killian syndrome which is caused by the presence of an abnormal extra chromosome called an isochromosome 12p in a proportion of body cells.
Genetic disease
Published in Janet M Rennie, Giles S Kendall, A Manual of Neonatal Intensive Care, 2013
Janet M Rennie, Giles S Kendall
Ophthalmological examination can be invaluable. One or two genetic diseases can be diagnosed with serum biochemical tests, perhaps the best-known example being Smith–Lemli–Opitz syndrome in which there is an elevated 7-dehydrocholesterol concentration. Some genetic disorders only ever occur as mosaics (e.g. Pallister–Killian syndrome), so that a skin biopsy has to be done to make the diagnosis because white cell chromosomes will be normal.
Managing respiratory complications in infants and newborns with congenital diaphragmatic hernia
Published in Expert Opinion on Orphan Drugs, 2020
Sandeep Shetty, Fahad M. S. Arattu Thodika, Anne Greenough
CDH can present in isolation or associated with other congenital anomalies [9]. The incidence of associated anomalies ranges from 10%-40% [10]. The most common associated anomaly is congenital heart disease with an incidence ranging from 10% to 35% [11]. The frequently associated chromosomal anomalies include trisomies 18, 13, and 21 [12]. The other noticeable genetic syndromes associated with CDH are Fryns syndrome and Pallister-Killian Syndrome [13]. The presence of major congenital anomalies is an independent predictor of survival and is associated with grave prognosis [13]. A single ventricle or total mixing lesions are associated with a lower survival rate compared to duct dependent lesions or non-mixing lesions [14].
Chromosomal microarray analysis detects trisomy 9 mosaicism in a prenatal case not revealed by conventional cytogenetic analysis of cord blood
Published in Journal of Obstetrics and Gynaecology, 2019
Hai-Shen Tang, De-Gang Wang, Lv-Yin Huang, Dong-Zhi Li
Like most other chromosome disorders, trisomy 9 mosaicism manifests with a low-birth weight and a wide spectrum of mental disabilities and multiple anomalies, although the overall phenotypes can vary widely between individuals (Arnold et al. 1995). Most of the cases were diagnosed after birth, and prenatal cases have also been reported to be associated with variable levels of mosaicism ranging from 3 to 99% (Bruns 2011). In prenatal diagnosis, three different levels of mosaicism can be detected in vitro on the amniotic fluid cells (Hsu and Benn 1999). Level 3 mosaicism is regarded as true mosaicism, which is present in foetal tissues. There is a study that investigated the foetal blood karyotyping in pregnancies with true mosaicism in amniotic fluid cell culture (Shalev et al. 1994). The authors concluded that, in the presence of amniotic fluid cell true mosaicism and normal karyotype in foetal blood, the continuation of the pregnancy is safe and is to be recommended. However, this might be a pitfall in the prenatal diagnosis of chromosomal mosaicism. As evidenced by our case, only 1% (1 in 100 cells) trisomy 9 mosaicism was detected by foetal cord lymphocyte karyotyping in the same blood with 60–70% mosaicism for trisomy 9. A single abnormal cell might be interpreted as an artefact of cell culture. Indeed, at least three similar cases have also been reported, in which trisomy 9 cells were found in the amniotic fluid cell cultures, but not in cord lymphocyte cultures (Sherer et al. 1992; Merino et al. 1993). The discordance might be due to several reasons. The chromosomal analysis of blood is done by stimulating peripheral T-lymphocyte cells using phytohemagglutinin (PHA). The aneuploid cells might be under-represented in the T-cell population in the circulation, if they are less competitive than the normal cells in the growth from the stem cell populations. Furthermore, the trisomy cell line can fail to respond to mitogens. For example, it is well-known that in Pallister–Killian syndrome patients, PHA fails to stimulate i(12p) lymphocytes to divide. The diagnosis of this disorder is confirmed by the use of chromosome analysis on cultured skin fibroblasts (Reeser and Wenger 1992). This data indicates that a foetal cord blood cytogenetic analysis may not be considered as providing an accurate diagnosis of foetal trisomy 9.