Postnatal Identification of Trisomy 21: An Overview of 7,133 Postnatal Trisomy 21 Cases Identified in a Diagnostic Reference Laboratory in China

Abstract

This study describes the cytogenetic characteristics of 7,133 trisomy 21 (Tri21) identified from 247,818 consecutive postnatal cases karyotyped in a single reference laboratory in China for a period of 4 years. The average detection rate of Tri21 is 2.88% ranging from 3.39% in 2011 to 2.52% in 2014. The decreased detection rates over the years might reflect a possible impact of noninvasive prenatal testing applied rapidly in China and elective termination of affected pregnancies. 95.32% of the Tri21 karyotypes are standard Tri21, 4.53% are Robertsonian Tri21, and less than 1% are other Tri21 forms. There are more mosaic Tri21 in older children and adults, consistent with previous observations that clinical features in individuals with mosaic Tri21 are generally milder and easily missed during perinatal period. The male/female (M/F ratio) for the total 7,133 Tri21 cases and for the 6,671 cases with non-mosaic standard Tri21 are 1.50 and 1.53 respectively, significantly higher than the 0.93 for all the 247,818 cases we karyotyped, the 1.30 for the Down syndrome (DS) identified during perinatal period in China, and the 1.20 for the livebirth in Chinese population. In contrast, the mosaic standard Tri21 case has a significantly lower proportion of males when compared with the non-mosaic standard Tri21, indicating different underlying mechanisms leading to their formations. Opposite M/F ratios in different subtypes of ROB Tri21 were observed. A long list of rare or private karyotypes where Tri21 are concurrently present was identified. The large collection of Tri21 cases with a diversity of clinical findings and a wide age range allowed us to determine the frequency of the different karyotypes of Down syndrome in China, given the fact that this kind of national epidemiological data is lacking currently.

Bilingualism in children with a dual diagnosis of Down syndrome and Autism Spectrum Disorder

“…For the case study participant who had mosaic DS, although her language and phonological awareness abilities were lower than the TD children, her NVMA was equivalent to 6;3, which was not significantly different to all control groups and was only slightly below her chronological age (6;8). This would be in line with research that shows that children with mosaic DS usually do not experience cognitive impairments to the same extent as children with trisomy 21 (Korbel et al, 2009;Papavassiliou et al, 2015;Zhao et al, 2015).…”

Changes in maternal age and prevalence of congenital anomalies during the enactment of China's universal two-child policy (2013–2017) in Zhejiang Province, China: An observational study

“…In our study, among those infants from this group who lived, the proportion of CHDs, chromosomal anomalies, and body surface anomalies increased over the time frame of the policy changes. The current Chinese literature on BDs predominantly focuses on perinatal, live births in China [28,34,54,55]. Studies on infants born before 28 gestational weeks whose BDs were identified in the pre-prenatal period are scarce.…”

The importance of understanding individual differences in Down syndrome

“…Research on parental origin or the mechanism of mosaicism is currently sparse, making it difficult to identify the main mechanism. While mosaicism has sometimes been claimed to yield a milder cognitive phenotype 9 , 11 , data addressing this are very sparse and, where they do exist, the degree of mosaicism does not correlate with phenotypic severity. Interestingly, though, mosaicism provides an excellent opportunity to study phenotypic differences, since disomic and trisomic cell lines derived from mosaics only differ in the extra chromosome 21 12 .…”