Abstract:Tetrasomy 18p syndrome (Online Mendelian Inheritance in Man 614290) is a very rare chromosomal disorder that is caused by the presence of isochromosome 18p, which is a supernumerary marker composed of two copies of the p arm of chromosome 18. Most tetrasomy 18p cases are de novo cases; however, familial cases have also been reported. It is characterized mainly by developmental delays, cognitive impairment, hypotonia, typical dysmorphic features, and other anomalies. Herein, we report de novo tetrasomy 18p in a… Show more
“…NGS showed that they had the genotype dup(18)(p11.32→p11.21)×4. It has been reported that the clinical symptoms are likely isochromosome 18p [i(18p)] syndromes or tetrasomy 18p syndrome, which feature neonatal feeding problems, hypoevolutism, and high risk of infections [ 5 , 6 ]. Fig.…”
Section: Resultsmentioning
confidence: 99%
“…There may be a hot breakpoint located at 18(p11.21). In region 18p, approximately 67 genes can contribute to the phenotypes, including AFG3L2, MC2R, and TGIF1, which are associated with developmental disorders [5,6]. So, when taking care of patient 61259, pay attention to artificial feeding, avoiding infections, and evaluating affected organs and systems.…”
Background: Small supernumerary marker chromosomes (sSMCs) are rare structural abnormalities in the population; however, they are frequently found in children or fetuses with hypoevolutism and infertile adults. sSMCs are usually observed first by karyotyping, and further analysis of their molecular origin is important in clinical practice. Nextgeneration sequencing (NGS) combined with Sanger sequencing helps to identify the chromosomal origins of sSMCs and correlate certain sSMCs with a specific clinical picture. Results: Karyotyping identified 75 sSMCs in 74,266 samples (0.1% incidence). The chromosomal origins of 27 of these sSMCs were detected by sequencing-related techniques (NGS, MLPA and STR). Eight of these sSMCs are being reported for the first time. sSMCs mainly derived from chromosomal X, Y, 15, and 18, and some sSMC chromosomal origins could be correlated with clinical phenotypes. However, the chromosomal origins of the remaining 48 sSMC cases are unknown. Thus, we will develop a set of economical and efficient methods for clinical sSMC diagnosis. Conclusions: This study details the comprehensive characterization of 27 sSMCs. Eight of these sSMCs are being reported here for the first time, providing additional information to sSMC research. Identifying sSMCs may reveal genotype-phenotype correlations and integrate genomic data into clinical care.
“…NGS showed that they had the genotype dup(18)(p11.32→p11.21)×4. It has been reported that the clinical symptoms are likely isochromosome 18p [i(18p)] syndromes or tetrasomy 18p syndrome, which feature neonatal feeding problems, hypoevolutism, and high risk of infections [ 5 , 6 ]. Fig.…”
Section: Resultsmentioning
confidence: 99%
“…There may be a hot breakpoint located at 18(p11.21). In region 18p, approximately 67 genes can contribute to the phenotypes, including AFG3L2, MC2R, and TGIF1, which are associated with developmental disorders [5,6]. So, when taking care of patient 61259, pay attention to artificial feeding, avoiding infections, and evaluating affected organs and systems.…”
Background: Small supernumerary marker chromosomes (sSMCs) are rare structural abnormalities in the population; however, they are frequently found in children or fetuses with hypoevolutism and infertile adults. sSMCs are usually observed first by karyotyping, and further analysis of their molecular origin is important in clinical practice. Nextgeneration sequencing (NGS) combined with Sanger sequencing helps to identify the chromosomal origins of sSMCs and correlate certain sSMCs with a specific clinical picture. Results: Karyotyping identified 75 sSMCs in 74,266 samples (0.1% incidence). The chromosomal origins of 27 of these sSMCs were detected by sequencing-related techniques (NGS, MLPA and STR). Eight of these sSMCs are being reported for the first time. sSMCs mainly derived from chromosomal X, Y, 15, and 18, and some sSMC chromosomal origins could be correlated with clinical phenotypes. However, the chromosomal origins of the remaining 48 sSMC cases are unknown. Thus, we will develop a set of economical and efficient methods for clinical sSMC diagnosis. Conclusions: This study details the comprehensive characterization of 27 sSMCs. Eight of these sSMCs are being reported here for the first time, providing additional information to sSMC research. Identifying sSMCs may reveal genotype-phenotype correlations and integrate genomic data into clinical care.
“…The frequency of tetrasomy 18p is 1/140,000 in live newborns [22], which is the most common type among all these isochromosomes [23]. Their clinical characteristics include moderate to severe intellectual disability, developmental delay, microcephaly, typical dysmorphic features, and other anomalies, such as muscle tone abnormalities [24,25]. Cat eye syndrome (CES) is a rare developmental disorder with an incidence of 1/150,000 to 1/50,000 in liveborn infants [26].…”
Background To define the genotype-phenotype correlation of small supernumerary marker chromosomes (sSMCs) and conduct precise genetic counseling, we retrospectively searched and reviewed de novo sSMC cases detected during prenatal diagnosis at The First Affiliated Hospital of Zhengzhou University. Chromosome karyotypes of 20,314 cases of amniotic fluid from pregnant women were performed. For 16 samples with de novo sSMCs, 10 were subjected to single-nucleotide polymorphism (SNP) array or low-coverage massively parallel copy number variation sequencing (CNV-seq) analysis. Results Among the 10 sSMC cases, two sSMCs derived from chromosome 9, and three sSMCs derived from chromosomes 12, 18 and 22. The remaining 5 cases were not identified by SNP array or CNV-seq because they lacked euchromatin or had a low proportion of mosaicism. Four of them with a karyotype of 47,XN,+mar presented normal molecular cytogenetic results (seq[hg19] 46,XN), and the remaining patient with a karyotype of 46,XN,+mar presented with Turner syndrome (seq[hg19] 45,X). Five sSMC samples were mosaics of all 16 cases. Conclusion Considering the variable origins of sSMCs, further genetic testing of sSMCs should be performed by SNP array or CNV-seq. Detailed molecular characterization would allow precise genetic counseling for prenatal diagnosis.
“…In absence of (rare) malformations, a prenatal ultrasound diagnosis is very difficult because the only prenatal sign could be aspecific growth retardation. For this reason, without an invasive test, most cases are detected after birth …”
Circulating cell-free DNA, having no procedural risk of miscarriage, is the most suitable sample for a noninvasive prenatal testing (NIPT). Here we report on a boy, who came to our attention for hypotonia and psychomotor delay when he was 16 months old. During the pregnancy his mother performed a NIPT that resulted compatible with the presence of trisomy 18. A confirmatory invasive procedure has been proposed, but not performed, because the family preferred to follow a conservative line. A series of ultrasound excluded the presence of any major malformations. Genetic tests, performed after birth, revealed the presence of a tetrasomy 18p with an extra isochromosome 18p. Our report wants to underline the importance of an invasive procedure and consequent cytogenetic analysis in case of NIPT results indicating autosomal trisomies because under it may hide the presence of other structural chromosomal anomalies. These conditions are normally not visible at prenatal ultrasound or using combined test (CT) and the only identifiable not invasive sign could be the results of high risk at NIPT.
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