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False positive results for trisomy 18 from DNA-based noninvasive prenatal screening were caused, in two of the four patients who were evaluated, by maternal copy-number variation in chromosome 18. Methods of noninvasive prenatal screening 1 have advanced rapidly in clinical practice, with aneuploidy screening based on analysis of circulating cfDNA now routinely offered to women with high-risk pregnancies. Owing to the high reported accuracy of these screening tests, 2 , 3 attention has shifted to low-risk cohorts, in which the reduced incidence of aneuploidy may limit the positive predictive value of noninvasive prenatal screening. 4 A recent prospective analysis of cfDNA-based noninvasive prenatal screening in 1914 low-risk pregnancies showed false positive rates of 0.3%, 0.2%, and 0.1% for trisomies 21, 18, and 13, respectively — rates that were lower than those observed with . . .

BackgroundRing chromosome 18 (r[18]) is a rare syndrome in which one or both ends of chromosome 18 are lost and the remaining chromosome rejoins to form ring-shaped figures. It is characterized by developmental delay/cognitive disability, facial dysmorphisms, and immunological problems. The phenotype associated with epilepsy is rare and has not yet been reported in China.MethodsWe report herein the case of a 12-year-old Chinese girl who presented with typical facial dysmorphisms, developmental delay, cognitive disability, hyperactivity, and epilepsy and discuss the clinical features of r(18) syndromes through comparison with previously described cases worldwide.ResultsWe describe the characteristics of all seizures that have been reported in these cases and propose that the appearance of epilepsy in r(18) patients may be associated with the abnormality of chromosome karyotypes. Further studies are warranted to confirm this.

Background A plethora of cases are reported in the literature with iso- and ring-chromosome 18. However, co-occurrence of these two abnormalities in an individual along with a third cell line and absence of numerical anomaly is extremely rare. Case presentation A 7-year-old female was referred for diagnosis due to gross facial dysmorphism and severe developmental delay. She presented with dysmorphic features, hypo/hyper pigmentation of the skin, intellectual disability and craniosynostosis. G-banding chromosome analysis suggested mos 46,XX,psu idic(18)(p11.2)[25]/46,XX,r(?18)[30]. Additional analysis by molecular karyotyping suggested pure partial deletion of 15 Mb on 18p (18p11.32p11.21). Lastly, multiple rearrangements and detection of a third cell line (ring chr18 and interstitial deletion) of chr18 was observed by multi-color banding. Conclusion The current study presents a novel case of chromosomal abnormalities pertaining to chromosome 18 across 3 cell lines, which were delineated with a combinatorial approach of diagnostic methods.

Purpose: To determine whether maternal plasma cell–free DNA sequencing can effectively identify trisomy 18 and 13. Methods: Sixty-two pregnancies with trisomy 18 and 12 with trisomy 13 were selected from a cohort of 4,664 pregnancies along with matched euploid controls (including 212 additional Down syndrome and matched controls already reported), and their samples tested using a laboratory-developed, next-generation sequencing test. Interpretation of the results for chromosome 18 and 13 included adjustment for CG content bias. Results: Among the 99.1% of samples interpreted (1,971/1,988), observed trisomy 18 and 13 detection rates were 100% (59/59) and 91.7% (11/12) at false-positive rates of 0.28% and 0.97%, respectively. Among the 17 samples without an interpretation, three were trisomy 18. If z -score cutoffs for trisomy 18 and 13 were raised slightly, the overall false-positive rates for the three aneuploidies could be as low as 0.1% (2/1,688) at an overall detection rate of 98.9% (280/283) for common aneuploidies. An independent academic laboratory confirmed performance in a subset. Conclusion: Among high-risk pregnancies, sequencing circulating cell–free DNA detects nearly all cases of Down syndrome, trisomy 18, and trisomy 13, at a low false-positive rate. This can potentially reduce invasive diagnostic procedures and related fetal losses by 95%. Evidence supports clinical testing for these aneuploidies. Genet Med 2012:14(3):296–305

Despite the advent of genomic sequencing, molecular diagnosis remains unsolved in approximately half of patients with Mendelian disorders, largely due to unclarified functions of noncoding regions and the difficulty in identifying complex structural variations. In this study, we map a unique form of central iris hypoplasia in a large family to 6q15-q23.3 and 18p11.31-q12.1 using a genome-wide linkage scan. Long-read sequencing reveals a balanced translocation t(6;18)(q22.31;p11.22) with intergenic breakpoints. By performing Hi-C on induced pluripotent stem cells from a patient, we identify two chromatin topologically associating domains spanning across the breakpoints. These alterations lead the ectopic chromatin interactions between APCDD1 on chromosome 18 and enhancers on chromosome 6, resulting in upregulation of APCDD1 . Notably, APCDD1 is specifically localized in the iris of human eyes. Our findings demonstrate that noncoding structural variations can lead to Mendelian diseases by disrupting the 3D genome structure and resulting in altered gene expression. Here, the authors identify a form of central iris hypoplasia affecting the pupillary zone. They suggest that noncoding structural variations can lead to Mendelian diseases by disrupting the 3D genome structure and resulting in altered gene expression.

Ring 18 syndrome or ring chromosome 18 is an extremely rare genetic disorder involving the fusion of the 18th chromosomal ends to form a ring, often with genetic material loss of varying degrees. Although clinical presentation can be extremely variable, characteristic features usually include craniofacial malformations, delayed development, hypotonia, and other skeletal and congenital heart defects. We report the management of a 20-year-old male with ring chromosome 18 who underwent general anesthesia for dental treatment. Clinical manifestations for this patient included intellectual disability, short stature, hypertelorism, flat nasal bridge, micrognathia, a “carp-shaped” mouth, and aortic and pulmonary valve regurgitation. Although mask ventilation and oral intubation were easily performed, nasal intubation was difficult because of rhinostenosis. When providing general anesthesia for a patient with ring chromosome 18, anesthesiologists should evaluate the patient preoperatively for congenital heart defects and prepare for a potential difficult airway.

Abstract Objectives Data characterizing the cytogenetic landscape of intravascular large B-cell lymphoma (ILBCL) are limited. Here, we developed a comprehensive karyotypic data set to identify recurrent cytogenetic abnormalities in ILBCL. Methods Cases of ILBCL with complete cytogenetic analysis were identified from an institutional database and the literature. The combined data were systematically reviewed for the presence of recurrent abnormalities. Results Four new cases were identified and combined with 25 karyotypes previously published in the literature. Karyotypes were uniformly complex with a median of 10 aberrations. In total, 72.4% had abnormalities involving chromosome 1, with 31.0% involving rearrangements of 1p13 or 1q21; 58.6% had abnormalities involving chromosome 6, which in almost all cases involved 6q; 34.5% had abnormalities involving chromosome 14, with 27.6% involving rearrangements of 14q32; and 55.2% had abnormalities of chromosome 18, with 37.9% harboring trisomy 18. Conclusions Recurrent cytogenetic abnormalities involving chromosomes 1, 6q, and 18 are present in greater than 50% of ILBCL.

Background Ring 18 chromosome is a rare chromosomal aberration associated with a wide range of symptoms affecting all organ systems. One possible symptom associated with this condition is an orofacial cleft. However, to date, there are very few reported cases where the cleft has been surgically treated. Case Description In our case study, we present a female patient with Ring 18 chromosome who underwent cleft palate surgery at 14 months of age. Subsequently, a reoperation of the palate was necessary due to wound dehiscence. For the secondary reconstruction of the palate, the acellular dermal matrix (ADM) MatriDerm® was used to improve healing. The cleft palate surgery progressively improved her ability to take in food, allowing a transition from nasogastric tube feeding to oral intake. Results This is only the fourth reported case of a child with Ring 18 chromosome undergoing surgical correction of an orofacial cleft. Additionally, it is one of the first cases where an ADM MatriDerm® was used in the surgical correction of a cleft palate. In this study, we also present a comprehensive literature review, providing an overview of the various symptoms associated with this syndrome. Conclusion Cleft palate surgery had a very positive effect on improving food intake in the patient with Ring 18 chromosome. The use of an acellular dermal matrix during the secondary cleft palate surgery led to improved healing and a good outcome.

Background Complex chromosomal rearrangement (CCR) refers to a structural rearrangement involving at least two chromosomes or a minimum of three breakpoints. CCR may lead to intellectual disability, structural anomalies, infertility, and recurrent miscarriages. Chromosome karyotyping and chromosomal microarray analysis (CMA) are unable to detect complex chromosomal rearrangements. As multiple diagnostic approaches are available in clinical practice for detecting chromosomal structural abnormalities and copy number variations—each with its own advantages and limitations—selecting the appropriate testing method is crucial for effective clinical management. Optical genome mapping (OGM) is an advanced genomic technology that utilizes ultra-long single-molecule analysis to comprehensively detect chromosomal aberrations and structural variants at high resolution. Material and methods Amniocentesis was performed for a 36-year-old multipara (advanced maternal age), with subsequent comprehensive fetal genetic analysis including chromosome karyotyping, CMA, and OGM. Family members underwent peripheral blood karyotyping and OGM. Results The fetal karyotype derived from amniotic fluid was 46,XN,?ins(18)(q21.2;p11.31p11.2). CMA demonstrated duplications of four segments and a deletion of one segment on chromosome 18. Therefore, OGM was performed on the fetal and family members to further elucidate the chromosomal structure. The fetus has derived CCRs on chromosome 18 of maternal origin. In contrast, both the mother and the second daughter, who carried the identical CCRs, were phenotypically normal. Conclusion OGM is of significant importance in the diagnosis and characterization of CCRs. OGM plays a critical role in diagnosing complex chromosomal rearrangements and has proven to be invaluable in clinical utility.

Background 18p deletion (18p-) syndrome is a rare chromosomal abnormality with a wide range of phenotypes. Its main clinical features are short stature, intellectual disability, and facial dysmorphism, which are rarely accompanied by autoimmune thyroid disease (ATD) or pituitary abnormalities. Herein, we report the first Chinese patient with a de novo 18p deletion who presented with ATD and non-functioning pituitary adenoma. Case presentation A 24-year-old female patient presented with severe ptosis, intellectual disability, hypothyroidism associated with Hashimoto’s thyroiditis, and a non-functional pituitary adenoma. Deletion of the short arm of chromosome 18 was detected in a G-banded karyotyping (46, XX, del [18] [p11.1]). Chromosomal microarray analysis revealed a 14.9 Mb deletion in chromosome 18p11.32p11.21, defined as arr[GRCh38]18p11.32p11.21(136227–15079295)x1. The literature review indicated that patients with 18p- syndrome and ATD were predominantly female with early disease onset (mean age: 15 years). Conclusions 18p- syndrome is associated with ATD and pituitary abnormalities. Therefore, endocrine system evaluation and genetic analysis of the 18p breakpoint region are valuable for predicting patient prognosis.