Molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from chromosome 8 or r(8)(::p11.22→q11.21::) in an 18-year-old female with short stature, obesity, attention deficit hyperactivity disorder, and intellectual disability

Analysis of genetic characteristics of 436 children with dysplasia and detailed analysis of rare karyotype

Chromosomal abnormality is one of the important causes of dysplasia in children. However, due to regional and ethnic differences, the reported rates of chromosomal abnormalities in patients with dysplasia vary greatly. Moreover, the clinical manifestations in children with rare chromosomal diseases were heterogeneous. So, we retrospectively analyzed the karyotype results of 436 children with dysplasia and conducted a detailed analysis of rare chromosomal diseases. The results showed that chromosomal abnormalities were present in 181 of 436 cases. Intellectual disability, dysmorphology, congenital malformations, the disorder of sexual development, and short stature were the main five clinical symptoms in children with chromosomal abnormalities. Moreover, 136 cases of Trisomy 21 (Tri21) were detected, of which 130 were standard Tri21, 5 were robertsonian Tri21, and 1 was chimera type. In addition, 16 cases of rare abnormal karyotype, including complex Tri21, complex Turner syndrome, 4p-syndrome, 18q-syndrome, and 5p-syndrome, were also detected. In summary, chromosome abnormality is one of the important causes of dysplasia in children. Furthermore, prenatal screening and diagnosis could play a great significance in preventing dysplasia in children. In addition, the retrospective analysis of rare cases is valuable for clinical diagnosis and risk assessment of recurrence.

Whole Exome Sequencing Facilitated the Identification of a Mosaic Small Supernumerary Marker Chromosome (sSMC)

Small supernumerary marker chromosomes (sSMCs) are a group of rare chromosomal anomalies, which pose challenges in the clinical practice of prenatal diagnosis and genetic counseling. This study enrolled an extended family with an underage male patient displaying infantile seizures, intellectual disability, and retarded speech and psychomotor function. A series of multiplatform genetic detections was conducted to explore the diagnostic variation. Whole exome sequencing (WES) and chromosomal microarray analysis (CMA) indicated a mosaic sSMC derived from the pericentromeric region of chromosome 8 in the patient, which was confirmed using cytogenetic methods. The proband and his mother, who carried this mosaic variant, exhibited strong phenotypic variability. We also ruled out the pathogenicity of a KDM5C variant by extended validation. Our results emphasized the capacity of WES to detect mosaic SMCs and the importance of mosaic ratios in the appearance and severity of symptomatic phenotypes.

Molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from chromosome 8 associated with congenital hypoplasia of the tongue and review of the literature

OBJECTIVE

To present molecular cytogenetic characterization of mosaic supernumerary ring chromosome 8 which has trisomy of a region of chromosome 8p12-q21.13 associated with congenital hypoplasia of the tongue and review of the literature.

CASE REPORT

A 27 year-old woman presented with congenital hypoplasia of the tongue. The chromosome karyotype of peripheral blood lymphocytes was detected by conventional cytogenetic analysis. The genome copy number variations were detected by SNP array. Conventional cytogenetic analysis of the peripheral blood revealed a karyotype of 47,XX,+mar[60]/46,XX[40]. SNP array revealed that there was a duplication of 45.2 Mb at arr[hg19] 8p12q21.13(36,013,636-81,263,140) × 2-3.

CONCLUSION

With this study a patient involving mosaic trisomy 8p12-q21.13 along with clinical properties, is described and compared to previously reported cases involving a small supernumerary marker chromosome (sSMC) derived from chromosome 8.

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from chromosome 21q11.2-q21.1 and a literature review

OBJECTIVE

We present prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome (sSMC) derived from chromosome 21q11.2-q21.1, and we review the literature of an sSMC(21) with a duplication of 21q11.2-q21.1.

CASE REPORT

A 40-year-old woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XX,+mar [18]/46,XX [4]. The parental karyotypes were normal. Prenatal ultrasound findings were unremarkable. aCGH analysis of cultured amniocytes revealed a 2.855-Mb duplication of 21q11.2-q21.1 encompassing the genes of LIPI, ABCC13 and NRIP1. Metaphase fluorescence in situ hybridization analysis on cultured amniocytes revealed a result of 47,XX,+mar .ish der(13/21) (D13/21Z1+) [10]. Spectral karyotyping analysis determined the origin of chromosome 21 in the sSMC. A female fetus was delivered with no phenotypic features of Down syndrome and no structural abnormalities. We discuss the genotype-phenotype correlation of LIPI, ABCC13 and NRIP1, and review the literature of an sSMC(21) associated with dup(21)(q11.2q21.1).

CONCLUSION

aCGH is useful for identification of the nature and genetic component of a prenatally detected sSMC.

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from chromosome 11

OBJECTIVE

We present prenatal diagnosis and molecular cytogenetic characterization of a small supernumerary marker chromosome (sSMC) derived from chromosome 11.

CASE REPORT

A 37-year-old, gravida 3, para 2, woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XX,+mar[18]/46,XX[4]. The parental karyotypes were normal. Level II ultrasound findings were unremarkable. Array comparative genomic hybridization (aCGH) on the DNA extracted from cultured amniocytes revealed no genomic imbalance. The sSMC was characterized by spectral karyotyping (SKY) using 24-color SKY probes and fluorescence in situ hybridization (FISH) using a whole chromosome paint (wcp) probe and a CEP11 (D11Z1) probe. The result was 47,XX,+mar.ish(11)(SKY+, wcp11+, D11Z1+)[16]/46,XX[4], indicating that the sSMC was derived from chromosome 11. A healthy female baby was delivered at 37 weeks of gestation with no phenotypic abnormalities. The cord blood had a karyotype of 47,XX,+mar[32]/46,XX[8]. Polymorphic DNA marker analysis of the blood excluded uniparental disomy 11. The female infant was normal in growth and psychomotor development during follow-ups at two months of age.

CONCLUSION

aCGH, SKY and FISH are useful in prenatal diagnosis of an sSMC derived from the centromeric region of a non-acrocentric chromosome.