Proximal 21q deletion as a result of a de novo unbalanced t(12;21) translocation in a patient with dysmorphic features, hepatomegaly, thick myocardium and delayed psychomotor development

A case of monosomy 21 presented with difficult tracheal intubation

Background

Monosomy 21 is a rare chromosomal abnormality. It is mainly associated with mental retardation, intellectual disability, growth retardation, microcephaly, and characteristic facial features. General anesthesia in adults with this disease has not been reported. We report difficult airway management of an adult patient with monosomy 21.

Case description

A 30-year-old female was scheduled for laparoscopic gynecological surgery. She was diagnosed with monosomy 21 at birth and accompanied with mental retardation. Preoperative examination revealed limited mouth opening with Mallampati score of IV, but no abnormal laboratory test or chest X-P. Anesthesia was performed using general anesthesia with epidural analgesia. Although bag-mask ventilation was improved by a muscle relaxant, mouth opening was further restricted, and laryngoscope insertion was impossible. Tracheal intubation was achieved using a bronchofiberscope. The operation procedure was completed, and the patient was discharged from the hospital without any major postoperative complications.

Conclusions

In this patient, mouth opening was further reduced after induction of general anesthesia with a muscle relaxant. Preoperative evaluation and adequate preparation of airway management are important for general anesthesia in an adult patient with monosomy 21.

Spread of X-chromosome inactivation into autosomal regions in patients with unbalanced X-autosome translocations and its phenotypic effects

Patients with unbalanced X-autosome translocations are rare and usually present a skewed X-chromosome inactivation (XCI) pattern, with the derivative chromosome being preferentially inactivated, and with a possible spread of XCI into the autosomal regions attached to it, which can inactivate autosomal genes and affect the patients' phenotype. We describe three patients carrying different unbalanced X-autosome translocations, confirmed by G-banding karyotype and array techniques. We analyzed their XCI pattern and inactivation spread into autosomal regions, through HUMARA, ZDHHC15 gene assay and the novel 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay, and identified an extremely skewed XCI pattern toward the derivative chromosomes for all the patients, and a variable pattern of late-replication on the autosomal regions of the derivative chromosomes. All patients showed phenotypical overlap with patients presenting deletions of the autosomal late-replicating regions, suggesting that the inactivation of autosomal segments may be responsible for their phenotype. Our data highlight the importance of the XCI spread into autosomal regions for establishing the clinical picture in patients carrying unbalanced X-autosome translocations, and the incorporation of EdU as a novel and precise tool to evaluate the inactivation status in such patients.

De novo mosaic and partial monosomy of chromosome 21 in a case with superior vena cava duplication

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.

Psychiatric Disorders and Distal 21q Deletion-A Case Report

Partial deletion of chromosome 21q is a very rare genetic condition with highly variable phenotypic features including heart defects, high or cleft palate, brain malformations (e.g., cerebral atrophy), developmental delay and intellectual disability. So far, there is very limited knowledge about psychiatric disorders and their effective treatment in this special population. To fill this gap, the authors present the case of an initially five-year-old girl with distal deletion (del21q22.2) and comorbid oppositional defiant disorder (main psychiatric diagnosis) covering a period of time of almost four years comprising initial psychological/psychiatric assessment, subsequent treatment with Parent-Child Interaction Therapy (PCIT), and follow-up assessments. Post-intervention results including a 19-month follow-up indicated good overall efficacy of PCIT and high parental satisfaction with the treatment. This case report makes a substantial contribution to enhancing knowledge on psychiatric comorbidity and its effective treatment in patients with terminal 21q deletion. Moreover, it emphasizes the necessity of multidisciplinarity in diagnosis and treatment due to the variety of anomalies associated with 21q deletion. Regular screenings for psychiatric disorders and (if indicated) thorough psychological and psychiatric assessment seem to be reasonable in most affected children, as children with developmental delays are at increased risk of developing psychiatric disorders. As demonstrated with this case report, PCIT seems to be a good choice to effectively reduce disruptive behaviors in young children with partial deletion of chromosome 21q.

Detection of 21q11.2-q22.11 deletions in a fetus by NIPT

Background

Non‐invasive prenatal testing (NIPT) is extensively used in the detection of fetal trisomies 21, 18, and 13, which is promptly becoming a common clinical practice. Concerned about the clinical application of non‐invasive detection of the fetal autosomal duplications or deletion.

Case Presentation

A 34‐year‐old, healthy pregnant woman was referred to the First Affiliated Hospital of the Air Force Medical University. The ultrasound examination indicates that low‐lying placenta, the fetus has a left ventricular bright spot and small amount of pericardial effusion. NIPT was chosen to further screen for fetal chromosomal abnormalities. NIPT results indicated an approximately 18 Mb deletion, which was verified by prenatal diagnosis. The chromosome microarray analysis (CMA) result showed about 19.2 Mb deletions in 21q11.2‐q22.11. The karyotype analysis result showed 46,XN,del(21)(q11.2q22.1). Prenatal diagnosis was consistent with NIPT results, and the paternal karyotype revealed no obvious abnormalities.

Conclusion

In this study, we successfully detected and diagnosed deletions of large fragments in chromosome 21 in a fetus using NIPT. This indicates that NIPT can provide effective genetic information for detecting fetal subchromosomal deletions/duplications.

Monosomy chromosome 21 compensated by 21q22.11q22.3 duplication in a case with small size and minor anomalies

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.