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Genetic counseling of mosaicism for a deletion due to partial monosomy in a cell line with 46 chromosomes associated with a normal cell line at amniocentesis remains difficult because mosaic deletion due to partial monosomy has been reported to be associated with either normal or abnormal phenotype in prenatal diagnosis. This article makes a comprehensive review of the reported cases of mosaicism for a deletion due to partial monosomy in a cell line with 46 chromosomes associated with a normal cell line at amniocentesis and various counseling issues such as culture artefact, cytogenetic discrepancy between cultured and uncultured amniocytes and among various tissues, perinatal progressive decrease of the abnormal cell line and a possible favorable fetal outcome. The information provided is useful for obstetricians and genetic counselors during genetic counseling of the parents who wish to keep the babies under such a circumstance.

The phenotype of structural chromosome 18 mutations is heterogenous, the clinical manifestations may range from mild to severe, they have been widely studied in the literature, however, there are few cases where two or more mutations are present in the same individual, reports where these alterations are caused by a maternal pericentric inversion and diagnosed prenatally are even rarer. Affected individuals are generally characterized by low birth weight, intellectual disability, heart defects, musculoskeletal abnormalities, craniofacial anomalies, among others. We describe the case of a masculine fetus from a non-consanguineous marriage obtained at week 29 of gestation. 27-year-old mother, G2C1, she started antenatal care at week 11 of pregnancy in the Hospital Universitario del Valle, in Cali, Colombia. Ultrasound at the 11th week of gestation showed a 3.9 mm nuchal translucency (>95p), subsequently at week 18th a new ultrasound found a 6mm nuchal translucency (>95p); suspecting a chromosomal aberration an amniocentesis was carried out at week 18th, a 756-band resolution karyotype reported: 18 partial trisomy (from 18p.11.2 down to the centromere and from 18q11.22 to 18qter), and partial 18 monosomy (from 18pter to 18p11.2 and from the centromere to 18q11.2). The parents also underwent genetic testing, the karyotype of the mother exhibited a pericentric inversion of the 18 chromosome (46,XX,inv(18)(p11.2q11.2), no abnormalities were found in the father’s genetic material. At week 24 of gestation detailed anatomy ultrasound showed left diaphragmatic hernia, multicystic dysplastic kidney, and polyhydramnios. After explaining the diagnosis and providing genetic counseling, the patient requested voluntary interruption of pregnancy as established by the c-355/06 law of the Colombian constitutional court. A 1,180 g fetus as obtained. The structural rearrangement of this case may be explained by an error in maternal meiosis, oogenesis. During meiosis 2 an anomalous disjunction in the chromosome 18 took place, where the two short arms were separated from the long arms, the latter isochromosome was the one that the fetus received, thus, leading to the described mutation. The aim of this case report is to provide to the scientific literature the first case of prenatal diagnosis of a fetus with partial trisomy and partial monosomy of specific bands of the chromosome 18, due to maternal pericentric inversion, while also highlighting the value of early prenatal diagnosis, in order to make choices regarding voluntary interruption of pregnancy, pregnancy follow up, or planning the delivery method, and allowing adequate genetic and reproductive counseling for future pregnancies.

Genetic counseling of mosaicism for a deletion due to partial monosomy in a cell line with 46 chromosomes associated with a normal cell line at amniocentesis remains difficult because mosaic deletion due to partial monosomy has been reported to be associated with either normal or abnormal phenotype in prenatal diagnosis. This article makes a comprehensive review of the reported cases of mosaicism for a deletion due to partial monosomy in a cell line with 46 chromosomes associated with a normal cell line at amniocentesis and various counseling issues such as culture artefact, cytogenetic discrepancy between cultured and uncultured amniocytes and among various tissues, perinatal progressive decrease of the abnormal cell line and a possible favorable fetal outcome. The information provided is useful for obstetricians and genetic counselors during genetic counseling of the parents who wish to keep the babies under such a circumstance., Competing Interests: Declaration of competing interest The authors have no conflicts of interest relevant to this article., (Copyright © 2024. Published by Elsevier B.V.)

Abstract Background Full or partial monosomy of chromosome (chr) 21 is a very rare abnormal cytogenetic finding. It is characterized by variable sizes and deletion breakpoints on the long arm (q) of chr 21 that lead to a broad spectrum of phenotypes that include an increased risk of birth defects, developmental delay and intellectual deficit. Case presentation We report a 37-year-old G1P0 woman initially screened by non-invasive prenatal testing with no positive findings that was followed by an 18-week anatomy scan with a fetal finding of duplication of the superior vena cava (SVC). The medical and family history was otherwise uneventful. After appropriate genetic counseling, amniocentesis was performed to evaluate suspected chromosomal anomalies. Conclusions Interphase fluorescent in situ hybridization revealed loss of one chr 21 signal that was further delineated by chromosomal microarray analysis on uncultured amniocytes as a terminal 10 Mb deletion on chr 21q. Karyotype and microarrays on cultured amniocytes showed two cell lines for a mosaic 21q terminal deletion and monosomy 21. The combined molecular cytogenetics results reported following the ISCN 2016 guideline as mos 46,XX,del(21)(q22)dn[20]/45,XX,-21dn[10].nuc ish(D21S342/D21S341/D21S259x1)[100].arr[GRCh37] 21q11.2q22.12(15412676_36272993)x1~2,21q22.12q22.3(36431283_47612400)x1. Parental chromosomal analysis revealed normal karyotypes. Thus, this was a de novo mosaic full and partial monosomy of chr 21 in a case with SVC duplication. Despite the association of congenital heart disease with monsomy 21 we could not find any published literature or online databases for this cytogenetic abnormality. The patient terminated the pregnancy following the abnormal molecular cytogenetic results due to the possible challenges the baby would face if carried to term.

Abstract Background Partial monosomy 21 is a rare finding with variable sizes and deletion breakpoints, presenting with a broad spectrum of phenotypes. Case presentation We report a 10-month-old boy with short stature, minor anomalies and mild motor delay. The patient had a monosomy 21 and duplication of the 21q22.11q22.3 region on the remaining derivative chromosome 21 which represents a partial 21q uniparental disomy of paternal origin, upd(21q22.11q22.3)pat. The abnormalities were characterized by karyotyping, FISH, chromosomal microarray, and genotyping. Conclusions This is the first case showing a monosomy 21 compensated by upd(21q22.11q22.3) as a mechanism of genomic rescue. Because there is no strong evidence showing imprinting on chromosome 21, the uniparental disomy itself is not associated with abnormal phenotype but has reduced phenotype severity of monosomy 21. We reviewed the previously published cases with isolated 21q deletions and identified a common deletion of 5.7 Mb associated with low birth weight, length and head circumference in the 21q21.2 region.

Background: IInterstitial 21q deletions can cause a wide spectrum of symptoms depending on the size and the location of the deletion. It has previously been suggested that the long arm of chromosome 21 can be divided into three regions based on the clinical severity of the patients and deletion of the region from 32.3 Mb to 37.1 Mb was more crucial than the deletion of other regions. Case Presentation: In this study we describe a female patient with dysmorphic features, hepatomegaly, thick myocardium and psychomotor delay. Conventional karyotyping was initially interpreted as full monosomy 21, but subsequent chromosome microarray analysis suggested an approximately 18 Mb partial monosomy. Re-evaluation of the karyotype and fluorescence in situ hybridization revealed deletion of the proximal 21q11.2-q22.11 segment and insertion of 21q22.11-qter to 12qter. The deletion of the present case overlaps with two of the proposed regions including part of the proposed crucial region. Conclusions: This report emphasizes the relevance of investigating suspected full monosomies with high resolution methods and FISH in order to investigate the extent of the deletion and the presence of more complex rearrangements. [ABSTRACT FROM AUTHOR]

Objective: To assess the postnatal clinical manifestation of an antenatally detected unbalanced rearrangement involving chromosome 13 in an ethnic South Indian couple. Methods: We used conventional cytogenetics on fetal cells obtained from prenatal specimens and on peripheral blood lymphocytes from consanguineous family members to ascertain the chromosomal abnormalities. Results: We report the reproductive outcomes of a maternally inherited chromosome translocation involving chromosome 9 and 13 and the informed decisions of the couple, after genetic counseling in India, regarding their 4 pregnancies. Conclusion: This case report highlights the current practice in India of offering prenatal diagnosis and preimplantation genetic diagnosis to individuals who are carriers of balanced translocations, to reduce the risk of conceiving chromosomally abnormal offspring. [ABSTRACT FROM AUTHOR]

Lindstrand A, Malmgren H, Sahlén S, Schoumans J, Nordgren A, Ergander U, Holm E, Anderlid BM,Blennow E. Detailed molecular and clinical characterization of three patients with 21q deletions. We have investigated three patients with 21q deletions, two with developmental delay, dysmorphic features and internal organ malformations, and one with cognitive function within the normal range but with some deficits in gross and fine motor development. All aberrations were characterized by array-comparative genomic hybridization (array-CGH). In addition, extensive fluorescence in situ hybridization (FISH) mapping on metaphase chromosomes and mechanically stretched chromosomes was performed on patient 1 who had an extremely complex intrachromosomal rearrangement with 16 breakpoints, four deletions and four duplications. Patients 2 and 3 had interstitial deletions comprising 21q21.1-21q22.11 and 21q11.2-21q21.3, respectively. Partial deletions of 21q are rare and these patients display a highly variable phenotype depending on the size and position of the deletion. A review of the literature identified 38 cases with pure 21q deletions. Twenty-three of these had reliable mapping data. The combined information of present and previous cases suggests that the ITSN1 gene is involved in severe mental retardation in patients with 21q deletion. In addition, a critical region of 0.56 Mb containing four genes, KCNE1, DSCR1, CLIC6 and RUNX1, is associated with severe congenital heart defects, and deletions of the most proximal 15–17 Mb of 21q is associated with mild or no cognitive impairment, but may lead to problems with balance and motor function. [ABSTRACT FROM AUTHOR]

Presents a case study of an infant with insertion, inversion and deletion of chromosome 6. Background of the patient; Clinical presentation of the patient; Findings of the cytogenetic analysis of the patient.

This paper presents the family of a dysmorphic child with the phenotypic features of Turner’s syndrome and 5q trisomy, whose parents are both carriers of a balanced translocation. The parents’ karyotypes are 46,X,t(X;5)(p11.1;q31) and 45,XY,der(13;14)(q10;q10), respectively. [Copyright &y& Elsevier]