A Peruvian Child with 18p-/18q+ Syndrome and Persistent Microscopic Hematuria

The molecular mechanisms of recombinant chromosome 18 with parental pericentric inversions and a review of the literature

Chromosomal rearrangements mostly result from non-allelic homologous recombination mediated by low-copy repeats (LCRs) or segmental duplications (SDs). Recent studies on recombinant chromosome 18 (rec (18)) have focused on diagnoses and clinical phenotypes. We diagnosed two cases of prenatal rec (18) and identified precise breakpoint intervals using karyotype and chromosomal microarray analyses. We analyzed the distribution characteristics of breakpoint repetitive elements to infer rearrangement mechanisms and reviewed relevant literature to identify genetic trends. Among the 12 families with 25 pregnancies analyzed, 68% rec (18), 24% spontaneous abortions, and 8% normal births were reported. In the 17 rec (18) cases, 65% presented maternal origin and 35% were paternal. Short-arm breakpoints at p11.31 were reported in 10 cases, whereas the long-arm breakpoints were located at q21.3 (6 cases) and q12 (4 cases). Breakpoints of pericentric inversions on chromosome 18 are concentrated in p11.31, q21.3, and q12 regions. Rearrangements at 18p11.31 are non-recurrent events. ALUs, LINE1s, and MIRs were enriched at the breakpoint regions (1.85 to 3.42-fold enrichment over the entire chromosome 18), while SDs and LCRs were absent. ALU subfamilies had sequence identities of 85.94% and 83.01% between two pair breakpoints. Small repetitive elements may mediate recombination-coupled DNA repair processes, facilitating rearrangements on chromosome 18. Maternal inversion carriers are more prone to abnormal recombination in prenatal families with rec (18). Recombinant chromosomes may present preferential segregation during gamete formation.

A Pseudocoarctation of the Aorta With a Left Subclavian Artery Aneurysm, A Case Report and A Review of the Literature

Here we present a 47-year-old male diagnosed with a pseudocoarctation of the aorta and a funnel-like subclavian artery aneurysm with a large orifice and severe aortic valve insufficiency. The patient underwent a two-stage repair for both pathologies. After an aortic valve replacement, postcardiotomy pericardial effusion occurred and was medically managed. Six months later, the patient underwent a distal arcus aorta and subclavian artery replacement with a left posterolateral thoracotomy as the second stage. Due to the strict adhesions, pulmonary veins were not cannulated and an extracorporeal bypass between the pulmonary artery and femoral artery was used for distal body perfusion. The coincidence of subclavian aneurysms and a pseudocoarctation of the aorta is rare and a literature review was performed to identify treatment options for this pathology.

Pseudocoarctation of aorta: a very rare anatomic anomaly

Pseudocoarctation of the aorta (PCOA) is a rare anomaly of the aortic arch and its presentation is often an incidental finding. We present the case of a 66-year-old patient with a history of high blood pressure, who was admitted for surgical management of bicuspid aortic valve disease with severe insufficiency and who was incidentally detected to have a PCOA. It was decided to manage the latter conservatively and go ahead with surgical aortic valve replacement, to address the problem that led to his admission to the hospital. The patient had a favorable postoperative course and was discharged in a stable condition with an advice for periodic follow-up as out-patient consultations.

Prenatal diagnosis and molecular cytogenetic characterization of partial dup(18q)/del(18p) due to a paternal pericentric inversion 18 in a fetus with multiple anomalies

OBJECTIVE

We present prenatal diagnosis of rec(18)dup(18q)inv(18)(p11.2q21.2)pat owing to paternal pericentric inversion in a fetus.

CASE REPORT

A 37-year-old woman was diagnosed with multiple anomalies on a prenatal ultrasound scan at 17 weeks and 5 days of gestation. She underwent amniocentesis at 20 weeks and 2 days. Conventional karyotyping of amniocyte showed 46, XX, der(18). She was thus referred for genetic counseling; cytogenetic analysis revealed a 46, XY karyotype, inv(18)(p11.2q21.2), of the father. Therefore, based on the results of the father, the fetal karyotype was defined as 46, XX, rec(18)dup(18q)inv(18)(p11.2q21.2)pat. Array comparative genomic hybridization of amniocytes to obtain specific information showed a 3-Mb deletion of 18p11.31p11.32 (136227_3100353)x1 and a 23.7-Mb duplication of 18q21.31-q23 (54222717_77957375) × 3.

CONCLUSION

Maternal serum screening produces normal results for 18p-/18q+ syndrome, but it can be diagnosed by fluorescent in situ hybridization, quantitative-fluorescent polymerase chain reaction, or array comparative genomic hybridization test by observing abnormal findings on ultrasound.

Cytogenetic, Molecular, and Phenotypic Characterization of a Patient with de novo Derivative Chromosome 18 and Review of the Literature

We present a patient with a de novo derivative chromosome 18 which includes a terminal deletion of 18p and a terminal duplication of 18q accompanied by a cryptic duplication of 18p. The girl had mild dysmorphic features such as micro-retrognathia, upslanted palpebral fissures, bilateral epicanthus, high palate, low-set ears, short neck, and full cheeks. She also had an H-type tracheoesophageal fistula which required surgery. Her cognitive and motor skills were delayed. Karyotype analysis showed an additional segment on the short arm of chromosome 18. Chromosomal microarray revealed a 7.3-Mb terminal loss from 18p11.32 to 18p11.23, a 22.2-Mb terminal gain from 18q21.31 to 18q23, and a 3.9-Mb interstitial gain from 18p11.22 to 18p11.21. We hypothesize that the mother has gonadal mosaicism for normal chromosome 18, der(18)dup(p11.22p11.21), and der(18)dup(p11. 22p11.21)inv(18)(p11.22q21.31), or both the terminal del/dup and the interstitial duplication occurred simultaneously.

Molecular cytogenetic identification of small supernumerary marker chromosomes using chromosome microarray analysis

Background

This study aimed to evaluate the feasibility of chromosomal microarray analysis (CMA) in detecting the origin and structure of small supernumerary marker chromosomes (sSMCs) in prenatal and postnatal cases and to clarify sSMC-related genotype-phenotype correlations.

Results

Thirty-three cases carrying sSMCs were identified by banding cytogenetics. Of these cases, twenty-nine were first characterized by CMA and only two by FISH. The remaining two cases were excluded for their refusal to accept further examination. The chromosomal origins of twenty-two cases were successfully identified, in which pathogenetic copy number variations (PCNVs) were found in sixteen cases, four cases showed variants of uncertain significance (VOUS), one case showed benign CNVs, and one case showed probable PCNVs. For the nine cases with negative CMA results, only one of them contained centromere heterochromatin likely due to its normal phenotype, whereas reasons for the remaining eight cases were uncertain. We also found that CMA results indicating pathogenic abnormalities further affect the rate of pregnancy termination.

Conclusions

This study showed that CMA combined with cytogenetic analysis is particularly effective in identifying sSMCs. However, in order to establish sSMC-related genotype-phenotype correlations, the inclusion of more sSMC cases will be necessary in future studies.

Genetics and genomics in Peru: Clinical and research perspective

Peruvians currently preserve in their DNA the history of 2.5 million years of human evolution and 150,000 years of migration from Africa to Peru or the Americas. The development of Genetics and Genomics in the clinical and academic field is shown in this review.