Trisomy 13 (T13) and trisomy 18 (T18) are chromosomal abnormalities with high mortality rates in the first year of life. Understanding differences in long-term survival between children with full vs mosaic or partial trisomy is crucial for prognosis and health care planning. To examine the differences in 10-year survival between children with full T13 and T18 vs those with mosaic or partial trisomy. This retrospective, population-based cohort study assessed liveborn infants with T13 and T18 in the Texas Birth Defects Registry (deliveries from January 1, 1999, to December 31, 2008). Follow-up was through December 31, 2018 (the last date available at the time of analyses) to allow for 10 years of follow-up for all infants. All analyses were conducted from January 1, 2022, to December 31, 2024. Cytogenetic status (full trisomy vs mosaic or partial trisomy). The primary outcome was survival to 10 years of age, assessed using Kaplan-Meier survival estimates. The association between cytogenetic status and mortality by 10 years of age was assessed using Cox proportional hazards regression to generate hazard ratios (HRs). Population attributable fraction was calculated to determine the percentage of survival attributable to mosaic or partial trisomy status. The study cohort included 798 infants (463 female infants [58.0%]; mean [SD] maternal age, 30.9 [8.0] years) with T13 (n = 295) or T18 (n = 503). Among all cases with T13, 25 infants (8.5%; 95% CI, 5.5%-12.3%) survived to 10 years of age. Similarly, among all infants with T18, 43 (8.6%; 95% CI, 6.3%-11.3%) survived to 10 years of age. Kaplan-Meier survival estimates to 10 years of age were statistically significantly higher among children with mosaic or partial trisomy (13 [25.0%] and 14 [43.8%], respectively) compared with full trisomy (12 [4.9%] and 29 [6.6%], respectively) (both P < .001). Infants with full trisomy had statistically significantly increased 10-year mortality hazards compared with those with mosaic or partial trisomy for both T13 (HR, 2.00; 95% CI, 1.42-2.82) and T18 (HR, 3.34; 95% CI, 2.08-5.38). The results of the calculated proportion of 10-year survival due to the presence of nonfull trisomy status (population attributable fraction) was 41.7% for children with T13 and 27.9% for children with T18. The findings of this cohort study of infants with T13 and T18 support differences in long-term survival based on cytogenetic status and emphasize the need to potentially reassess the context of these conditions generally being considered incompatible with life, particularly for those with mosaic trisomies. These findings offer context surrounding treatment decisions, such as withholding interventions, for affected infants in the future.

Chromosome 15q duplication (Dup15q) syndrome is a rare genetic disorder that presents with a range of psychiatric and neurological symptoms. To date, no cases have been reported involving a patient with a 300 kb microduplication on chromosome 15 presenting with developmental delay, intellectual disability, attention-deficit/hyperactivity disorder (ADHD), and epilepsy. We describe a 20-year-old male diagnosed with Dup15q syndrome at the age of nine. His early development was marked by congenital strabismus, global developmental delay, and intellectual disability, which required enrollment in a special education program until age 11. He also exhibited hyperactivity, aggression, and self-injurious behavior. Since then, both his motor and cognitive functions have progressively declined. At age 14, he was diagnosed with ADHD. Treatment with atomoxetine, methylphenidate, and risperidone provided partial symptom relief. However, escitalopram triggered episodes of severe tantrums and was subsequently discontinued. From the age of 16, he began experiencing epilepsy, characterized by focal seizures, generalized tonic-clonic seizures, and absence seizures. Valproic acid (VPA) was effective in significantly reducing his seizure activity. This case highlights that Dup15q syndrome associated with a 300 kb microduplication can predominantly affect the central nervous system and may respond favorably to atomoxetine, methylphenidate, risperidone, and VPA. Dup15q syndrome should be considered in the differential diagnosis of individuals presenting with developmental delay, intellectual disability, ADHD, and epilepsy.

Differentially methylated regions (DMRs) in certain areas of the genome are subject to genomic imprinting. DMRs at chromosome 11p15.5 are associated with Beckwith-Wiedemann syndrome (BWS) and Russell-Silver Syndrome (RSS), two growth disorders with opposite phenotypes. We identified a maternally inherited duplication containing part of the 11p15 DMR in a non-anomalous fetus in first trimester using genome sequencing (GS). The ∼281kb duplication at 11p15.5 contains the entire imprinting control region 1 (ICR1) and the H19 gene but lacks the IGF2 gene and the imprinting control region 2 (ICR2). Methylation studies revealed hypomethylation of ICR1 in fetal cells as well as in the mother (leukocytes), who had a history of feeding difficulties in infancy and short stature. The duplication was inherited from the asymptomatic maternal grandmother of the fetus, who showed hypermethylation of ICR1 in leukocytes suggesting paternal inheritance. The fetus developed decelerating growth in late gestation and phenotypes overlapping those of RSS were noted in infancy. This study adds to the limited literature on partial duplications of the 11p15.5 region and their associated phenotypes, underscoring the efficacy of GS in cases involving DMRs associated with imprinting disorders.

The 16p11.2 deletion syndrome is a clinically heterogeneous disorder, characterized by developmental delay, intellectual disability, hyperphagia, obesity, macrocephaly and psychiatric problems. Cases with 16p11.2 duplication syndrome have similar neurodevelopmental problems, but typically show a partial 'mirror phenotype' with underweight and microcephaly. Various copy number variants (CNVs) of the chromosomal 16p11.2 region have been described. Most is known about the 'typical' 16p11.2 BP4-BP5 (29.6-30.2 Mb; ~600 kb) deletions and duplications, but there are also several published cohorts with more distal 16p11.2 BP2-BP3 CNVs (28.8-29.0 Mb; ~220 kb), who exhibit clinical overlap. We assessed 100 cases with various pathogenic 16p11.2 CNVs and compared their clinical characteristics to provide more clear genotype-phenotype correlations and raise awareness of the different 16p11.2 CNVs. Neurodevelopmental and weight issues were reported in the majority of cases. Cases with distal 16p11.2 BP2-BP3 deletion showed the most severe obesity phenotype (73.7% obesity, mean BMI SDS 3.2). In addition to the more well defined typical 16p11.2 BP4-BP5 and distal 16p11.2 BP2-BP3 CNVs, we describe the clinical features of five cases with other, overlapping, 16p11.2 CNVs in more detail. Interestingly, four cases had a second genetic diagnosis and 18 cases an additional gene variant of uncertain significance, that could potentially help explain the cases' phenotypes. In conclusion, we provide an overview of our Dutch cohort of cases with various pathogenic 16p11.2 CNVs and relevant second genetic findings, that can aid in adequately recognizing, diagnosing and counseling of individuals with 16p11.2 CNVs, and describe the personalized medicine for cases with these conditions.

Pure partial trisomy 16q12.1q22.1 is a rare chromosome copy number variant (CNV). The primary clinical phenotypes associated with this syndrome include abnormal facial morphology, global developmental delay (GDD), short stature, and reported predisposing factors for atypical behavior, autism, the development of learning disabilities, and neuropsychiatric disorders. The dosage-sensitive genes associated with partial trisomy are not disclosed preventing to establish a genotype-phenotype correlation. We report a case of a Chinese patient diagnosed with GDD and an abnormal facial shape, who was found to have partial trisomy 16 through karyotyping and high-throughput sequencing analysis. Karyotype and CNV tracing analyses were also conducted on the biological parents of the patient to assess for any chromosomal structural abnormalities. Additionally, we included 29 patients with pure partial trisomy 16q, reported in the DECIPHER database and the literature. We and performed a genotype-phenotype correlation analysis. The proband, a 2-year-old female, was found to have a de novo 21.96 Mb duplication located between 16q12.1q22.1, with no other deletions observed on other chromosomes, indicating a pure partial trisomy of 16q. Through genotype and phenotype analysis of 29 individuals, we found that patients with the duplicated region located at the distal region of 16q may exhibit more severe symptoms than those with duplication at the proximal region; however, no relationship was identified between phenotype and the size of the duplicated segment. We report, for the first time, a patient with partial trisomy 16q validated by multiple genetic tests, including CNV-seq, whole exome sequencing (WES), and karyotyping. It is speculated that partial trisomy of 16q may be associated with continuous gene duplication. However, functional studies are necessary to identify the causative gene or critical region linked to duplication syndrome of chromosome 16q.