OBJECTIVE: To report on a case of mosaicism involving trisomy 21, maternal uniparental isodisomy, and normal diploid cells in uncultured amniocytes, and to explore the discrepancies between conventional cytogenetic and molecular cytogenetic techniques during prenatal diagnosis. METHODS: A 30-year-old pregnant woman who presented to Boai Hospital of Zhongshan on June 27, 2023 has undergone amniocentesis at 16 weeks of gestation. The amniotic fluid sample was subjected to quantitative fluorescent PCR (QF-PCR), G-banded karyotype analysis, and chromosomal microarray analysis (CMA). The discrepancies between the results of each method were analyzed. This study was approved by Medical Ethics Committee of Boai Hospital of Zhongshan (Ethics No.: KY-2024-001-01). RESULTS: Non-invasive prenatal testing (NIPT) at 12 weeks indicated a high risk of trisomy 21. QF-PCR of uncultured amniocytes revealed a pattern of trisomy 21. After one week of cell culture, G-banding analysis showed mos 47,XX,+21[1]/46,XX[72]. CMA revealed a homozygous state of chromosome 21 in cultured cells, while uncultured amniocytes showed mosaic trisomy 21 with an estimated proportion of 50%. These findings suggested a complex chromosomal mosaicism in the fetus, which may result from a trisomy rescue event during early embryogenesis, leading to coexistence of three cell lines including trisomy 21, maternal uniparental isodisomy, and normal diploid cells. CONCLUSION In prenatal diagnosis, discrepancies may arise between QF-PCR and conventional chromosomal karyotyping analysis, particularly in complex genetic phenomena such as trisomy rescue and uniparental disomy. For cases where NIPT indicated a high risk of trisomy 21 but G-banding karyotype analysis yielded a normal result, further molecular genetic testing using uncultured cells is recommended.
Humans ; Female ; Mosaicism ; Pregnancy ; Uniparental Disomy/diagnosis* ; Adult ; Down Syndrome/diagnosis* ; Prenatal Diagnosis/methods* ; Diploidy ; Karyotyping ; Amniocentesis

OBJECTIVE: To explore the genetic etiology of four fetuses with Uniparental disomy (UPD), and analyze their causes. METHODS: Four fetuses undergoing prenatal diagnosis at Wenzhou Central Hospital between November 2021 and July 2024 were selected as the study subjects. Genetic testing and diagnosis were carried out through G-banded chromosomal karyotyping, single nucleotide polymorphism array (SNP-array) and methylation multiplex ligation-dependent probe amplification (MS-MLPA). This study was approved by the Medical Ethics Committee of the Hospital (Ethics No.: L2024-11-028). RESULTS: The four cases of pathogenic UPD had involved chromosomes 2, 11, 15 and 16, respectively, of which 2 cases were accompanied by fetal ultrasound abnormalities, One fetus was shown a high risk by serological screening, while another showed a high risk by non-invasive DNA testing. The karyotype of fetus 1 was 45,X?,rob(13;15)(q10;q10), and its parents had both carried a Robertsonian translocation involving chromosomes 13 and 15, whilst the karyotypes of other three fetuses were all normal. Pedigree analysis indicated that the UPDs in three cases were paternally derived, and the remaining one was unknown. The causes of the four cases included imprinting syndrome in two cases, autosomal recessive disorder in one case, and cryptic mosaic trisomy in one case. CONCLUSION The clinical phenotypes of UPD are diverse, and the mechanisms are complex. Combined chromosomal karyotyping, SNP-array, MS-MLPA and other technologies are required to make a clear diagnosis for prenatal genetic counseling and postnatal management.
Humans ; Uniparental Disomy/diagnosis* ; Female ; Pregnancy ; Prenatal Diagnosis/methods* ; Polymorphism, Single Nucleotide/genetics* ; Karyotyping ; Adult ; Genetic Testing ; Male ; Fetus

OBJECTIVETo explore the genetic cause for a fetus with structural anomaly, and to correlate the phenotype with the genotype.

METHODSAmniotic fluid was obtained following the revelation of structural anomaly by ultrasonography. Cell culture and direct DNA extraction were performed in parallel. G-banded karyotyping analysis and chromosome microarray analysis (CMA) were subsequently carried out.

RESULTSG-banded karyotyping has suggested the fetus to be a normal male. However, CMA analysis has revealed the presence of a mosaic 3.24 Mb duplication of 1p36.33p36.32 (24%) and uniparental disomy (UPD) of chromosome 6. The genetic diagnosis for the fetus was therefore 46,XY, arr 1p36.33 p36.32(849,466-4,090,472)×2-3, (6)×2 hmz. The anomaly can probably explain the ultrasound findings in the fetus.

CONCLUSIONCompared with conventional cytogenetic methods, CMA has greater resolution and throughput, and can serve as a more efficient platform for the detection of chromosomal microdeletion, microduplication, loss of heterozygosity and UPD.

Adult ; Amniotic Fluid ; cytology ; metabolism ; Chromosome Aberrations ; Chromosome Duplication ; Chromosomes, Human, Pair 1 ; genetics ; Chromosomes, Human, Pair 6 ; genetics ; Female ; Fetal Diseases ; diagnosis ; genetics ; Humans ; Karyotyping ; Oligonucleotide Array Sequence Analysis ; methods ; Polymorphism, Single Nucleotide ; Pregnancy ; Prenatal Diagnosis ; methods ; Reproducibility of Results ; Sensitivity and Specificity ; Uniparental Disomy

OBJECTIVETo detect mosaic trisomy 9 missed by conventional cytogenetics.

METHODSPeripheral blood genomic DNA from a girl with mental retardation was analyzed using Affymetrix CytoScan (TM) HD array. Fluorescence in situ hybridization (FISH) was also performed on samples from two patients.

RESULTSThe SNP-array analysis has revealed multiple duplications along chromosome 9. FISH analysis showed that, for the peripheral blood sample from one patient, 40 of 100 interphase cells and 15 of 100 metaphase cells carried trisomy 9. For the cord blood sample from another patient, 35 of 100 interphase cells and 10 of 100 cultured cells carried trisomy 9.

CONCLUSIONSNP-array is useful for detecting low-level mosaicism which may be missed by conventional cytogenetics. Combined with karyotype and microarray analyses, FISH is a focused and targeted approach for diagnosing mosaic trisomy. They may provide a useful tool for differentiating pseudomosaicisms from true mosaicisms.

Adult ; Chromosomes, Human, Pair 9 ; genetics ; Female ; Humans ; In Situ Hybridization, Fluorescence ; Infant ; Male ; Mosaicism ; embryology ; Oligonucleotide Array Sequence Analysis ; instrumentation ; methods ; Polymorphism, Single Nucleotide ; Pregnancy ; Prenatal Diagnosis ; Trisomy ; diagnosis ; genetics ; Uniparental Disomy ; cytology ; diagnosis ; genetics

Prader-Willi syndrome (PWS) is a complex multisystem genetic disorder that is caused by the lack of expression of paternally inherited imprinted genes on chromosome 15q11-q13. This syndrome has a characteristic phenotype including severe neonatal hypotonia, early-onset hyperphagia, development of morbid obesity, short stature, hypogonadism, learning disabilities, behavioral problems, and psychiatric problems. PWS is an example of a genetic condition caused by genomic imprinting. It can occur via 3 main mechanisms that lead to the absence of expression of paternally inherited genes in the 15q11.2-q13 region: paternal microdeletion, maternal uniparental disomy, and an imprinting defect. Over 99% of PWS cases can be diagnosed using DNA methylation analysis. Early diagnosis of PWS is important for effective long-term management. Growth hormone (GH) treatment improves the growth, physical phenotype, and body composition of patients with PWS. In recent years, GH treatment in infants has been shown to have beneficial effects on the growth and neurological development of patients diagnosed during infancy. There is a clear need for an integrated multidisciplinary approach to facilitate early diagnosis and optimize management to improve quality of life, prevent complications, and prolong life expectancy in patients with PWS.
Body Composition ; DNA Methylation ; Early Diagnosis ; Genomic Imprinting ; Growth Hormone ; Humans ; Hyperphagia ; Hypogonadism ; Infant ; Learning Disorders ; Life Expectancy ; Muscle Hypotonia ; Obesity, Morbid ; Phenotype ; Prader-Willi Syndrome ; Quality of Life ; Uniparental Disomy

PURPOSE: Prader-Willi syndrome(PWS) is a complex disorder affecting multisystems with characteristic clinical features. Its genetic basis is an expression defect in the paternally derived chromosome 15q11-q13. We analyzed the clinical features and genetic basis of PWS patients for early detection and treatment. METHODS: We retrospectively studied 24 patients with PWS in Department of Pediatrics, Samsung Medical Center, from September 1997 to September 2001. We performed cytogenetic and molecular genetic techniques using high resolution GTG banding techniques, fluorescent in situ hybridization and methylation-specific PCR for CpG island of SNRPN gene region. RESULTS: The average birth weight of PWS patients was 2.67+/-0.47 kg and median age at diagnosis was 1.3 years. The average height and weight of PWS patients under one year at diagnostic time were located in a 3-10 percentile relatively, and a rapid weight gain was seen between two and six years. Feeding problems in infancy and neonatal hypotonia were the two most consistently positive major criteria in over 95% of the patients. In 18 of the 24 cases(75%), deletion of chromosome 15q11-q13 was demonstrated and one case among 18 had an unbalanced 14;15 translocation. In four cases without any cytogenetic abnormality, it may be considered as maternal uniparental disomy and the rest showed another findings. CONCLUSION: We suggest diagnostic testing for PWS in all infants/neonates with unexplained feeding problems and hypotonia. It is necessary for clinically suspicious patients to undergo an early genetic test. As the genetic basis of PWS was heterogenous and complex, further study is required.
Birth Weight ; Chromosome Aberrations ; CpG Islands ; Cytogenetics ; Diagnosis ; Diagnostic Tests, Routine ; Humans ; In Situ Hybridization, Fluorescence ; Molecular Biology ; Muscle Hypotonia ; Pediatrics ; Polymerase Chain Reaction ; Prader-Willi Syndrome* ; Retrospective Studies ; snRNP Core Proteins ; Uniparental Disomy ; Weight Gain

Prader-Willi(PW)syndrome is characterized by obesity, hypotonia, mental retardation, hypogonadism, short stature, excessive eating and characteristic facial appearance. Diabetes mellitus has been considered a component of PW syndrome. Recently this syndrome is caused by the absence of paternally derived genes normally located on chromosome segment 15 q11-q13 or may be the result of maternal uniparental disomy with the absence of paternally derived 15 q11-q13 region. The developement of probes containing segments of DNA from chromosome region 15 q11-q13 provides the oppotunity to confirm the diagnosis of PW syndrome by fluorescence in situ hybridization(FISH). We experienced a 15-year-old boy of PW syndrome with diabetes mellitus, who revealed mental retardation, hypogonadism, obesity and microdeletion of chromosome 15 q11-q13 comfirmed by FISH.
Adolescent ; Chromosomes, Human, Pair 15* ; Diabetes Mellitus ; Diagnosis ; DNA ; Eating ; Fluorescence ; Humans ; Hypogonadism ; Intellectual Disability ; Male ; Muscle Hypotonia ; Obesity ; Prader-Willi Syndrome* ; Uniparental Disomy