Cytogenetic and epidemiological findings in Down syndrome, England and Wales 1989 to 1993. National Down Syndrome Cytogenetic Register and the Association of Clinical Cytogeneticists (original) (raw)

Cytogenetic findings at Down syndrome and their correlation with clinical findings

Bosnian journal of basic medical sciences / Udruženje basičnih mediciniskih znanosti = Association of Basic Medical Sciences, 2005

Down syndrome is a genetic state characterized by trisomy of chromosome 21. In the retrospective study for 12 years period (1991-2002) we have conducted correlation between cytogenetics analyses and clinical findings in our centre at 96 male and 83 female patients. Down syndrome was confirmed by cytogenetics analyses in 84 (87.5%) male patients and excluded in 12 (12.5%) male patients. Down syndrome was confirmed by cytogenetics analyses in 71 (85.5%) female patients and excluded in 12 (14.5%) female patients. Most common karyotype is free trisomy found in 139 (89.7%) examinees, than follows translocation form determined in 9 (5.8%), and mosaicism determined in 7 (4.5%) examinees. Our results indicate that cytogenetics analyses are necessary to confirm diagnosis of Down syndrome.

Cytogenetic Analysis in Down Syndrome

Int J Hum …, 2010

Clinically diagnosed Down syndrome cases are referred for karyotyping and counseling. Data on incidence patterns of the 3 cytogenetic types of Down syndrome from the cases seen during the duration of 35 years is presented. Chromosomes were examined after G-banded technique of peripheral lymphocyte cultures. For each patient, in addition to the detailed case history in the proforma 15 metaphases were examined and in cases of mosaicism, the count was increased to 25 to 50 metaphases for analysis. A total of 874 cases were confirmed to have the karyotype of Down syndrome. 509 were male probands (58.24%) and 365 (41.76%) were female cases. The most common was free trisomy 21 in 759 (86.9%), translocation in 77 (8.8%) and mosaicism in 38 (4.3%) cases. Robertsonian translocation 14;21 (48;62.34%) was prevalent among the 77 cases with translocation and the remaining 29 cases had the translocation of chromosome 21 either to chromosomes 1 (1) or 15(2) or 21 (26). The sex ratio has indicated the prevalence of the males for the total sample (1.41:1) (509: 365) as well as for the 3 basic cytogenetic types of DS. Included in the male trisomy 21 are the 2 cases with Klinefelter syndrome (KFS)(48,XXY+21) and one with de novo Robertsonian translocation between chromosomes 13 and 14.

Molecular Cytogenetic Classification of Down Syndrome and Screening of Somatic Aneuploidy in Mothers

Cytogenetic and Genome Research

Down Syndrome (DS) caused by trisomy 21 results in various congenital and developmental complications in children. It is crucial to cytogenetically diagnose the DS cases early for their proper health management and to reduce the risk of further DS childbirths in mothers. In this study, we performed a cytogenetic analysis of 436 suspected DS cases using karyotyping and fluorescent in situ hybridization. We detected free trisomies (95.3%), robertsonian translocations (2.4%), isochromosomes (0.6%), and mosaics (1.2%). We observed a slightly higher incidence of DS childbirth in younger mothers compared to mothers with advanced age. We compared the somatic aneuploidy in peripheral blood of mothers having DS children (MDS) and control mothers (CM) to identify biomarkers for predicting the risk for DS childbirths. No significant difference was observed. After induced demethylation in peripheral blood cells, we did not observe a significant difference in the frequency of aneuploidy between ...

Cytogenetic abnormalities and clinical presentation in down syndrome patients

IP innovative publication pvt ltd, 2020

Total 60 samples were received for karyotyping from patients of developmental delay, dysmorphism and mental retardation, of which 20 cases showed trisomy 21. There was an equal incidence in males and females. All neonates (20%) showed broad short neck and decreased muscle tone at birth. Most common feature in infants (50%) was depressed nasal bridge and slanting eyes. All children (30%) presented with developmental delay and mental retardation. Low set ears and depressed nasal bridge (80%) was the most common finding across all age groups. Most common CHD was VSD (20%). Robertsonian translocation involving 14q and 21q was seen in 15 % cases. One case presented with transient abnormal myelopoiesis at birth. One case presented with additional balanced t(10;18)

Cytogenetic Analysis of Down Syndrome

Objective: Down syndrome is a common genetic disease, diagnosed with congenital malformation/mental retardation. Down syndrome occurs in all races & economic levels. It is caused by third copy of chromosome 21, there are there forms of DS. Simple Trisomy 21, Translocation Trisomy and Mosaic Trisomy. The aim of the study is to know cause of Down syndrome. Chromosomal analysis was carried out by G banding technique. Materials and Methods: 1 ml of peripheral blood samples were collected in Out Patient Department of pediatrics and Cytogenetic analysis was performed. Results: Out of 28, 3 female cases, 2 male cases were Down syndrome, All the 5 cases were free trisomy 21, which is common type of Down syndrome; we have not identified Robertsonian translocation and mosaic type of DS.

On the paternal origin of trisomy 21 Down syndrome

2010

Background: Down syndrome (DS), characterized by an extra free chromosome 21 is the most common genetic cause for congenital malformations and learning disability. It is well known that the extra chromosome 21 originates from the mother in more than 90% of cases, the incidence increases with maternal age and there is a high recurrence in young women. In a previous report we have presented data to indicate that maternal trisomy 21 (T21) ovarian mosaicism might provide the major causative factor underlying these patterns of DS inheritance. One important outstanding question concerns the reason why the extra chromosome 21 in DS rarely originates from the father, i.e. in less than 10% of T21 DS cases. We here report data indicating that one reason for this parental sex difference is a very much lower degree of fetal testicular in comparison to ovarian T21 mosaicism. Results: We used fluorescence in situ hybridisation (FISH) with two chromosome 21-specific probes to determine the copy number of chromosome 21 in fetal testicular cell nuclei from four male fetuses, following termination of pregnancy for a non-medical/social reason at gestational age 14-19 weeks. The cells studied were selected on the basis of their morphology alone, pending immunological specification of the relevant cell types. We could not detect any indication of testicular T21 mosaicism in any of these four male fetuses, when analysing at least 2000 cells per case (range 2038-3971, total 11.842). This result is highly statistically significant (p < 0.001) in comparison to the average of 0.54% ovarian T21 mosaicism (range 0.20-0.88%) that we identified in eight female fetuses analysing a total of 12.634 cells, as documented in a previous report in this journal. Conclusion: Based on these observations we suggest that there is a significant sex difference in degrees of fetal germ line T21 mosaicism. Thus, it would appear that most female fetuses are T21 ovarian mosaics, while in sharp contrast most male fetuses may be either very low grade T21 testicular mosaics or they may be non-mosaics. We further propose that this sex difference in germ line T21 mosaicism may explain the much less frequent paternal origin of T21 DS than maternal. The mechanisms underlying the DS cases, where the extra chromosome 21 does originate from the father, remains unknown and further studies in this respect are required.

A First Cytogenetic Study of Down Syndrome in Albania

International Journal of Science and Research (IJSR)

Down syndrome (DS) also known as trisomy 21 is a genetic complex disorder and the most common and best known autosomal chromosome abnormality in humans. Even though the majority of cases of DS can be identified based on clinical findings, cytogenetic analysis is essential to confirm the diagnosis and to provide information for genetic counseling. The present study is the first national consecutive series of Down Syndrome in Albanian population during the period 1984-2015. This study allowed the frequency of three basic cytogenetical types and the frequency of occurrence of the rarer karyotypes of Down syndrome to be estimated. Also the maternal age effect on the frequency of births of children with Down syndrome was evaluated. The frequency of occurrence of the different karyotypes was analyzed. The free trisomy 21 was the most common karyotype (nearly 91% of all cases). The ratio of mosaic trisomy 21 was 2.1%. The ratio of Robertsonian and reciprocal translocations were 5,7% and 0.2%, respectively. The chromosomal abnormalities (CAs) in addition to trisomy 21 were present in 0,8 % of all cases. Conclusions: Knowledge of the cytogenetic types are essential and carried out greatly helped in the management of these children and for counseling the affected families.

CytogeneticAnalysis of Down Syndrome in Gujarat

During 1995 to 2006, 382 cases clinically suspected for Down syndrome were investigated for cytogenetic study. Free trisomy 21 constituted 84.8% of cases, translocation 8.9%, mosaic 3.9% and in 2.4% cases regular T21 was associated with structural or numerical changes. Translocation was parentally inherited in 26.5% cases and maternal transmission was twice as common as paternal. Males were more pronounced to be affected than females in all the groups. 91.6% of DS babies were born to younger mothers (20-35 yr) compared to 8.4% in elderly mothers (>35 yr).

Down Syndrome: Parental Origin, Recombination, and Maternal Age

Genetic Testing and Molecular Biomarkers, 2012

The aims of the present study were to assess (1) the parental origin of trisomy 21 and the stage in which nondisjunction occurs and (2) the relationship between altered genetic recombination and maternal age as risk factors for trisomy 21. The study included 102 cases with Down syndrome from the Croatian population. Genotyping analyses were performed by polymerase chain reaction using 11 short tandem repeat markers along chromosome 21q. The vast majority of trisomy 21 was of maternal origin (93%), followed by paternal (5%) and mitotic origin (2%). The frequencies of maternal meiotic I (MI) and meiotic II errors were 86% and 14%, respectively. The highest proportion of cases with zero recombination was observed among those with maternal MI derived trisomy 21. A higher proportion of telomeric exchanges were presented in cases with maternal MI errors and cases with young mothers, although these findings were not statistically significant. The present study is the first report examining parental origin and altered genetic recombination as a risk factor for trisomy 21 in a Croatian population. The results support that trisomy 21 has a universal genetic etiology across different human populations.