De Novo Duplication of Chromosome 9p in a Female Infant: Phenotype and Genotype Correlation

An infant with trisomy 9 and partial trisomy 12 derived from maternal balanced translocation: A case report and literature review

We present here, a case of a neonate with an unbalanced chromosomal translocation due to a maternal chromosomal translocation carriage that resulted in the presence of trisomy 9p combined with a partial trisomy 12p. Karyotype analysis was performed using conventional cytogenetic chromosomal analysis using the GTG-banding technique. The mother was a carrier of a balanced chromosomal translocation of 46, XX, t(9;12)(q13;p11.2), that resulted in an unbalanced translocation of the offspring, who had a karyotype 47, XX, +der(9)t(9;12)(q13;p11.2)dmat, featuring a combined trisomy of 9q13→9pter region and 12p11.2→12pter region. Clinical phenotype of the infant included cephalo-facial deformity, growth retardation, hypertonia, opisthotonus, laryngeal wheezing, foot deformity, and congenital heart disease.

Uniparental disomy: expanding the clinical and molecular phenotypes of whole chromosomes

Uniparental disomy (UPD) refers to as both homologous chromosomes inherited from only one parent without identical copies from the other parent. Studies on clinical phenotypes in UPDs are usually focused on the documented UPD 6, 7, 11, 14, 15, and 20, which directly lead to imprinting disorders. This study describes clinical phenotypes and genetic findings of three patients with UPD 2, 9, and 14, respectively. Chromosomal microarray (CMA), UPDtool, methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) and whole-exome sequencing (WES) analysis were performed to characterize the genetic etiology. The CMA revealed a homozygous region involving the whole chromosome 2 and 9, a partial region of homozygosity in chromosome 14. UPD-tool revealed a paternal origin of the UPD2. MS-MLPA showed hypomethylation of imprinting gene MEG3 from maternal origin in the UPD14 case. In addition, UPD14 case displayed complex symptoms including growth failure, hypotonia and acute respiratory distress syndrome (ARDS), accompanied by several gene mutations with heterozygous genotype by WES analysis. Furthermore, we reviewed the documented UPDs and summarized the clinical characteristics and prognosis. This study highlighted the importance to confirm the diagnosis and origin of UPD using genetic testing. Therefore, it is suggested that expanding of the detailed phenotypes and genotypes provide effective guidance for molecule testing and genetic counseling, and promote further biological investigation to the underlying mechanisms of imprinted disorders and accompanied copy number variations.

Molecular cytogenetic characterization of a de novo derivative chromosome X with an unbalanced t(X;9) translocation in a fetus and literature review

Partial trisomy 9p is one of the most frequent autosome anomalies in newborn infants featured by craniofacial dysmorphism, intellectual disability and psychomotor growth. Female patients carrying monosomy Xq usually show mild symptoms due to skewed X-chromosome inactivation (XCI). Unbalanced translocation between chromosome X and chromosome 9 is rare in prenatal diagnosis. The skewed inactivation of abnormal X would spread into the extra segment of chromosome 9 presented in the der(X) leading to mild phenotypes. We reported on a fetus with high risk of trisomy 9p(13.32 Mb 9p23-p24.3 duplication)suggested by noninvasive prenatal testing (NIPT), the fetus was normal by ultrasonography. G-banding with trypsin-giemsa (GTG), copy number variations sequencing (CNV-seq) and fluorescence in situ hybridization (FISH) were carried out to delineate the nature of rearrangement. Final karyotype of the fetus was identified as 46,X,der(X)t(X;9)(q27;p23)dn. An unbalanced X-autosome translocation with a deletion of Xqter-q27.2 and a duplication of 9pter-p23 led to mild phenotypes with no obvious alteration by prenatal ultrasonography, or obvious pathological alterations after pregnancy termination.

Multi-institutional experience of genetic diagnosis in Ecuador: National registry of chromosome alterations and polymorphisms

BACKGROUND

Detection of chromosomal abnormalities is crucial in various medical areas; to diagnose birth defects, genetic disorders, and infertility, among other complex phenotypes, in individuals across a wide range of ages. Hence, the present study wants to contribute to the knowledge of type and frequency of chromosomal alterations and polymorphisms in Ecuador.

METHODS

Cytogenetic registers from different Ecuadorian provinces have been merged and analyzed to construct an open-access national registry of chromosome alterations and polymorphisms.

RESULTS

Of 28,806 karyotypes analyzed, 6,008 (20.9%) exhibited alterations. Down syndrome was the most frequent autosome alteration (88.28%), followed by Turner syndrome (60.50%), a gonosome aneuploidy. A recurrent high percentage of Down syndrome mosaicism (7.45%) reported here, as well as by previous Ecuadorian preliminary registries, could be associated with geographic location and admixed ancestral composition. Translocations (2.46%) and polymorphisms (7.84%) were not as numerous as autosomopathies (64.33%) and gonosomopathies (25.37%). Complementary to conventional cytogenetics tests, molecular tools have allowed identification of submicroscopic alterations regions or candidate genes which can be possibly implicated in patients' symptoms and phenotypes.

CONCLUSION

The Ecuadorian National Registry of Chromosome Alterations and Polymorphisms provides a baseline to better understand chromosomal abnormalities in Ecuador and therefore their clinical management and awareness. This data will guide public policy makers to promote and financially support cytogenetic and genetic testing.