Pure subtelomeric microduplications as a cause of mental retardation

Construction of copy number variation landscape and characterization of associated genes in a Bangladeshi cohort of neurodevelopmental disorders

Introduction: Copy number variations (CNVs) play a critical role in the pathogenesis of neurodevelopmental disorders (NDD) among children. In this study, we aim to identify clinically relevant CNVs, genes and their phenotypic characteristics in an ethnically underrepresented homogenous population of Bangladesh. Methods: We have conducted chromosomal microarray analysis (CMA) for 212 NDD patients with male to female ratio of 2.2:1.0 to identify rare CNVs. To identify candidate genes within the rare CNVs, gene constraint metrics [i.e., "Critical-Exon Genes (CEGs)"] were applied to the population data. Autism Diagnostic Observation Schedule-Second Edition (ADOS-2) was followed in a subset of 95 NDD patients to assess the severity of autism and all statistical tests were performed using the R package. Results: Of all the samples assayed, 12.26% (26/212) and 57.08% (121/212) patients carried pathogenic and variant of uncertain significance (VOUS) CNVs, respectively. While 2.83% (6/212) patients' pathogenic CNVs were found to be located in the subtelomeric regions. Further burden test identified females are significant carriers of pathogenic CNVs compared to males (OR = 4.2; p = 0.0007). We have observed an increased number of Loss of heterozygosity (LOH) within cases with 23.85% (26/109) consanguineous parents. Our analyses on imprinting genes show, 36 LOH variants disrupting 69 unique imprinted genes and classified these variants as VOUS. ADOS-2 subset shows severe social communication deficit (p = 0.014) and overall ASD symptoms severity (p = 0.026) among the patients carrying duplication CNV compared to the CNV negative group. Candidate gene analysis identified 153 unique CEGs in pathogenic CNVs and 31 in VOUS. Of the unique genes, 18 genes were found to be in smaller (<1 MB) focal CNVs in our NDD cohort and we identified PSMC3 gene as a strong candidate gene for Autism Spectrum Disorder (ASD). Moreover, we hypothesized that KMT2B gene duplication might be associated with intellectual disability. Conclusion: Our results show the utility of CMA for precise genetic diagnosis and its integration into the diagnosis, therapy and management of NDD patients.

A new case of 17p13.3p13.1 microduplication resulted from unbalanced translocation: clinical and molecular cytogenetic characterization

Copy number gain 17 p13.3p13.1 was detected by chromosomal microarray (CMA) in a girl with developmental/speech delay and facial dysmorphism. FISH studies made it possible to establish that the identified genomic imbalance is the unbalanced t(9;17) translocation of maternal origin. Clinical features of the patient are also discussed. The advisability of using the combination of CMA and FISH analysis is shown. Copy number gains detected by clinical CMA should be confirmed using FISH analysis in order to determine the physical location of the duplicated segment. Parental follow-up studies is an important step to determine the origin of genomic imbalance. This approach not only allows a most comprehensive characterization of an identified chromosomal/genomic imbalance but also provision of an adequate medical and genetic counseling for a family taking into account a balanced chromosomal rearrangement.

Prenatal detection of terminal 9p24.3 microduplication encompassing DOCK8 gene: A variant of likely benign

Trisomy 9p is one of the most common chromosomal partial trisomies in newborns. However, reports on prenatal 9p microduplications are rare in the clinic. This study aimed to examine the genotype-phenotype correlation and assess the clinical significance of 9p24.3 microduplication encompassing the DOCK8 gene. Eight pregnant women underwent amniocentesis for cytogenetic and genetic testing for various indications for prenatal diagnosis from January 2019 to January 2020. Chromosomal karyotypic analysis was performed on G-band metaphases that were prepared from cultured amniotic fluid cells. Chromosomal microarray analysis was carried out to detect chromosomal copy number variations. We also performed a literature review on clinical data on similar 9p24.3 microduplications to determine the genotype-phenotype correlation. We detected 123-248-kb microduplications in the region of 9p24.3 (chr9: 208454-469022), involving part of or the entire DOCK8 gene. The indications for prenatal diagnosis mainly focused on the risk of maternal serum screening for trisomy 21/18, advanced maternal age, and increased nuchal translucency. No evident structural abnormalities were observed for all fetuses, except for case 5 who presented with increased nuchal translucency in prenatal ultrasound findings. Follow-up of postnatal health was performed and showed no apparent abnormalities for cases 1 to 6 after birth. The parents of case 7 chose to terminate the pregnancy while the parents of case 8 chose to continue the pregnancy. We propose that 9p24.3 microduplications that encompass part of or the entire DOCK8 gene are variants that might be benign. However, further large-scale studies are necessary to evaluate the clinical pathogenicity. For prenatal cases with 9p24.3 microduplication, postnatal health and growth should be followed up and assessed regularly from childhood to adulthood.

Duplication of 9p24.3 in three unrelated patients and their phenotypes, considering affected genes, and similar recurrent variants

Background

Recent studies suggest that duplication of the 9p24.3 chromosomal locus, which includes the DOCK8 and KANK1 genes, is associated with autism spectrum disorders (ASD), intellectual disability/developmental delay (ID/DD), learning problems, language disorders, hyperactivity, and epilepsy. Correlation between this duplication and the carrier phenotype needs further discussion.

Methods

In this study, three unrelated patients with ID/DD and ASD underwent SNP aCGH and MLPA testing. Similarities in the phenotypes of patients with 9p24.3, 15q11.2, and 16p11.2 duplications were also observed.

Results

All patients with ID/DD and ASD carried the 9p24.3 duplication and showed intragenic duplication of DOCK8. Additionally, two patients had ADHD, one was hearing impaired and obese, and one had macrocephaly. Inheritance of the 9p24.3 duplication was confirmed in one patient and his sibling. In one patient KANK1 was duplicated along with DOCK8. Carriers of 9p24.3, 15q11.2, and 16p11.2 duplications showed several phenotypic similarities, with ID/DD more strongly associated with duplication of 9p24.3 than of 15q11.2 and 16p11.2.

Conclusion

We concluded that 9p24.3 is a likely cause of ASD and ID/DD, especially in cases of DOCK8 intragenic duplication. DOCK8 is a likely causative gene, and KANK1 aberrations a modulator, of the clinical phenotype observed. Other modulators were not excluded.

Gonadal mosaicism of large terminal de novo duplication and deletion in siblings with variable intellectual disability phenotypes

Background

Intellectual disability (ID) is a complex condition that can impact multiple domains of development. The genetic contribution to ID’s etiology is significant, with more than 100 implicated genes and loci currently identified. The majority of such variants are rare and de novo genetic mutations.

Methods

We have applied whole‐genome microarray to identify large, rare, clinically relevant copy number variants (CNVs). We have applied well‐established algorithms for variants call. Quantitative polymerase chain reaction (qPCR) was applied to validate the variants using three technical replicates for each family member. To assess whether the copy number variation was due to balanced translocation or mosaicism, we further conducted droplet digital PCR (ddPCR) on the whole family. We have, as well, applied “critical‐exon” mapping, human developmental brain transcriptome, and a database of known associated neurodevelopmental disorder variants to identify candidate genes.

Results

Here we present two siblings who are both impacted by a large terminal duplication and a deletion. Whole‐genome microarray revealed an 18.82 megabase (MB) duplication at terminal locus (7q34‐q36.3) of chromosome 7 and a 3.90 MB deletion impacting the terminal locus (15q26.3) of chromosome 15. qPCR and ddPCR experiments confirmed the de novo origin of the variants and the co‐occurrence of these two de novo events among the siblings, but their absence in both parents, implicates an unbalanced translocation that could have mal‐segregated among the siblings or a possible germline mosaicism. These terminal events impact IGF1R, CNTNAP2, and DPP6, shown to be strongly associated with neurodevelopmental disorders. Detailed clinical examination of the siblings revealed the presence of both shared and distinct phenotypic features.

Conclusions

This study identified two large rare terminal de novo events impacting two siblings. Further phenotypic investigation highlights that even in the presence of identical large high penetrant variants, spectrum of clinical features can be different between the siblings.

9q34.3 microduplications lead to neurodevelopmental disorders through EHMT1 overexpression

Both copy number losses and gains occur within subtelomeric 9q34 region without common breakpoints. The microdeletions cause Kleefstra syndrome (KS), whose responsible gene is EHMT1. A 9q34 duplication syndrome (9q34 DS) had been reported in literature, but it has never been characterized by a detailed molecular analysis of the gene content and endpoints. To the best of our knowledge, we report on the first patient carrying the smallest 9q34.3 duplication containing EHMT1 as the only relevant gene. We compared him with 21 reported patients described here as carrying 9q34.3 duplications encompassing the entire gene and extending within ~ 3 Mb. By surveying the available clinical and molecular cytogenetic data, we were able to discover that similar neurodevelopmental disorders (NDDs) were shared by patient carriers of even very differently sized duplications. Moreover, some facial features of the 9q34 DS were more represented than those of KS. However, an accurate in silico analysis of the genes mapped in all the duplications allowed us to support EHMT1 as being sufficient to cause a NDD phenotype. Wider patient cohorts are needed to ascertain whether the rearrangements have full causative role or simply confer the susceptibility to NDDs and possibly to identify the cognitive and behavioral profile associated with the increased dosage of EHMT1.

Rare structural variants in the DOCK8 gene identified in a cohort of 439 patients with neurodevelopmental disorders

Detection of copy number variations (CNVs) is a first-tier clinical diagnostic test for children with neurodevelopmental disorders (NDD), which reveals the genetic cause of the disorder in more than 20%. These are mostly known microdeletion/microduplication syndromes, but variants of unknown clinical significance (VOUS) and ambiguous CNVs can also be detected. An example of the last two are abnormalities in the DOCK8 gene. Conflicting interpretations of CNVs affecting DOCK8 can be found in the literature. Deletions were predicted to have a impact in carriers with variable clinical manifestations, where duplications have been proposed as benign variants. In our study, CNV screening was performed in a cohort involving 439 probands with suspected NDD. We identified known microdeletion/microduplication syndromes in 19% and VOUS CNVs in 8% of patients. Among these, three patients had a CNV encompassing the DOCK8 gene. Although diverse clinical presentations are noted in our three patients, comparison of their phenotypes revealed that abnormalities in cognition and communication, aggressive behaviour and mood swings are common to all of them. Therefore, a clinical relevance, in terms of influencing the psychiatric clinical picture of patients, is proposed for the CNVs disrupting the DOCK8 gene, regardless of whether it is a deletion or duplication.

16p subtelomeric duplication with vascular anomalies: an Albanian case report and literature review

A patient with karyotype 46,XY,der(4) was recognized by standard cytogenetic techniques, and presented with facial features, neurological impairment and pulmonary hypertension. Multiplex ligation-dependent probe amplification (MLPA) demonstrated duplication of the subtelomeric region of chromosome 16p and deletion of the subtelomeric region of chromosome 4q, suggesting a translocation between 4q and 16p. The karyotype of his parents was normal and their MLPA analysis also indicated a de novo imbalance. He had microcephaly, high frontal hairline, thin blond hair, bilateral blepharophimosis and palpebral ptosis, short nose, everted upper lip, cleft palate, micrognathia, cupped anteverted ears, hypoplastic distal phalanges and bilateral inguinal hernia. He also had pulmonary hypertension with tricuspidal regurgitation; cavernous liver hemangioma anomalies have been previously described in association with dup16p. We concluded that pulmonary and other vascular anomalies can be a feature of dup16p. We believe this is the first confirmed case of a 16p subtelomeric duplication with vascular anomalies identified in Albania.

Subtelomeric chromosomal rearrangements in a large cohort of unexplained intellectually disabled individuals in Indonesia: A clinical and molecular study

CONTEXT

Unbalanced subtelomeric chromosomal rearrangements are often associated with intellectual disability (ID) and malformation syndromes. The prevalence of such rearrangements has been reported to be 5-9% in ID populations.

AIMS

To study the prevalence of subtelomeric rearrangements in the Indonesian ID population.

MATERIALS AND METHODS

We tested 436 subjects with unexplained ID using multiplex ligation dependent probe amplification (MLPA) using the specific designed sets of probes to detect human subtelomeric chromosomal imbalances (SALSA P070 and P036D). If necessary, abnormal findings were confirmed by other MLPA probe kits, fluorescent in situ hybridization or Single Nucleotide Polymorphism array.

RESULTS

A subtelomeric aberration was identified in 3.7% of patients (16/436). Details on subtelomeric aberrations and confirmation analyses are discussed.

CONCLUSION

This is the first study describing the presence of subtelomeric rearrangements in individuals with ID in Indonesia. Furthermore, it shows that also in Indonesia such abnormalities are a prime cause of ID and that in developing countries with limited diagnostic services such as Indonesia, it is important and feasible to uncover the genetic etiology in a significant number of cases with ID.

Monosomy 9pter and trisomy 9q34.11qter in two sisters due to a maternal pericentric inversion

Pericentric inversions of chromosome 9 leading to unbalanced live-born offspring are relatively rare and so far only four cases have been reported. Here we present two sisters with an unbalanced recombinant chromosome 9 which resulted from a large maternal pericentric inversion inv(9)(p24.3q34.1). Further molecular characterisation of the aberrant chromosome 9 by 250k SNP array analysis showed a terminal 460 kb loss of 9p24.3 and a terminal 8.9 Mb gain of 9q34.11. We compared the clinical features of these two patients with the previous reported four cases as well as with patients with similar sized 9pter deletions or 9qter duplications. Based upon this study, we suggest that the recombinant chromosome 9 phenotype is mainly the result of duplication of a 3.4 Mb region of chromosome 9q34.11q34.13.

12p13 rearrangements: 6 Mb deletion responsible for ID/MCA and reciprocal duplication without clinical responsibility

Congenital balanced reciprocal translocations are one of the most frequent structural chromosomal aberrations in the population. We report a familial translocation t(12;22)(p13.3;pter) responsible for intellectual disabilities and congenital anomalies characterized by FISH and array CGH. Two patients carried a der(12)t(12;22)(p13.3;pter), resulting in a 6 Mb 12pter deletion. Patients presented with intellectual disabilities, pre- and post-natal growth retardation, ponderal development delay, global hypotonia, feeding problems and dysmorphic features. Two relatives presented with the reciprocal 12pter duplication, which had no clinical manifestations associated. For this translocation, we propose a mechanism based on a non-allelic recombination model, in which recombination of direct oriented segmental duplications between non-homologous chromatids leads to the reciprocal translocation. The characterization of this translocation has been critical for the family. Translocation carriers have a risk of 40% of having offspring carrying unbalanced products. 12p13.3 deletion carriers present with a recognizable syndrome and on the contrary, 12p13.3 duplication carriers present without clinical manifestations. Other published cases of 12p13.3 duplication show that this syndrome has a variable phenotype. It is advisable to delineate the duplication size and to discard other genetic aberrations, in order to give an accurate genetic counseling in patients carrying 12pter duplications.

"Familial" versus "sporadic" intellectual disability: contribution of subtelomeric rearrangements

Background

Cryptic subtelomeric rearrangements have been proposed as a significant cause of sporadic intellectual disability (ID) but the role of such aberrations in familial ID has not yet been studied. As positive family history of ID had been proposed as an important and significant predicting factor of subtelomeric rearrangements, it was assumed that the contribution of subtelomeric aberrations in familial ID would be much more than the sporadic ones. Three hundred and twenty two patients from 102 unrelated families with more than two ID patients in the first degree relatives have been investigated. Assessment of subtelomeric rearrangements were carried out using Multiplex Ligation-Dependent Probe Amplification (MLPA) technique. Detected aberrations were then confirmed by Fluorescence in Situ Hybridization (FISH) method.

Results

Among the families studied, 27.4% had 4-12, 36.3% had 3 and 36.3% had 2 affected individuals in the first degree relatives. One unbalanced translocation and 4 polymorphic changes were detected. The prevalence of clinically significant subtelomeric rearrangements was 0.98%.

Conclusion

This is the first investigation of subtelomeric aberrations in a large sample set of familial ID patients. Our results show that the contribution of subtelomeric rearrangements to familial ID is not as much as what had been determined for sporadic ones in the literature. Moreover, this study shows that the positive family history by alone, cannot be the most important and determining indicator of subtelomeric aberrations while it would be a good predicting factor when associated with dysmorphism or congenital malformations. These findings propose that other cryptic chromosomal abnormalities or even single gene disorders may be the main cause of familial ID rather than subtelomeric aberrations.

Unbalanced translocation 9;16 in two children with dysmorphic features, and severe developmental delay: Evidence of cross-over within derivative chromosome 9 in patient #1

We describe 2 children with dysmorphic features, and severe developmental delay presenting with overlapping unbalanced translocations of 9q34.3 and 16p13. Patient #1: A 4 year old African-American female with normal karyotype with a pericentric inversion on one chromosome 9 known to be a benign variant. Low resolution array CGH revealed a single BAC clone loss at 9q34.3 and a single BAC clone gain at 16p13.3, confirmed by FISH. Whole genome SNP array analysis refined these findings, identifying a terminal 1.28 Mb deletion (138,879,862-140,164,310) of 9q34.3 and a terminal 1.62 Mb duplication (45,320-1,621,753) of 16p13.3. Sub-telomeric FISH showed an unbalanced cryptic translocation involving the inverted chromosome 9 and chromosome 16. FISH of the father showed a balanced t(9;16)(q34.3;p13.3) involving the non-inverted chromosome 9, and a pericentric inversion on the normal 9 homologous chromosome. The presence of two rearrangements on chromosome 9, both an unbalanced translocation and a pericentric inversion, indicates recombination between the inverted and derivative 9 homologues from her father. Patient #2: A 1 year old Iraqi-Moroccan female with normal karyotype. Array-CGH identified a 0.56 Mb deletion of 9q34.3 (139,586,637-140,147,760) and an 11.31 Mb duplication of 16p13.3p13.13 (31,010-11,313,519). Maternal FISH showed a balanced t(9;16)(q34.3;p13.13). Both patients present with similar clinical phenotype.

Duplication 5q and deletion 9p due to a t(5;9)(q34;p23) in 2 cousins with features of Hunter-McAlpine syndrome and hypothyroidism

We report on 2 similarly affected cousins with a compound imbalance resulting from a familial t(5;9)(q34;p23) and entailing both an ∼17-Mb 5q terminal duplication and an ∼12-Mb 9p terminal deletion as determined by G-banding, subtelomere FISH, and aCGH. The proband's karyotype was 46,XX,der(9)t(5;9)(q34;p23)mat.ish der(9)t(5;9)(q34;p23)(9pter-,5qter+).arr 5q34q35(163,328,000-180,629,000)×3, 9p24p23(194,000-12,664,000)×1. Her cousin had the same unbalanced karyotype inherited from his father. The clinical phenotype mainly consists of a distinct craniofacial dysmorphism featuring microcephaly, flat facies, down slanting palpebral fissures, small flat nose, long philtrum, and small mouth with thin upper lip. Additional remarkable findings were craniosynostosis of several sutures, craniolacunia and preaxial polydactyly in the proband and hypothyroidism in both subjects. The observed clinical constellation generally fits the phenotypic spectrum of the 5q distal duplication syndrome (known also as Hunter-McAlpine syndrome), except for the thyroid insufficiency which can likely be ascribed to the concurrent 9p deletion, as at least 4 other 9pter monosomic patients without chromosome 5 involvement had this hormonal disorder. The present observation further confirms the etiology of the HMS phenotype from gain of the 5q35→qter region, expands the clinical pictures of partial trisomy 5q and monosomy 9p, and provides a comprehensive list of 160 patients with 5q distal duplication.

Subtelomeric microduplications in three sisters with moderate mental retardation

Copy number changes of subtelomeric regions are a common cause of mental retardation, occurring in approximately 5% of mentally retarded patients. New molecular techniques allow the identification of subtelomeric microduplications. We report a Tunisian family of three sisters with moderate mental retardation, facial dysmorphism, cardiopathy, and bilateral clinodactyly of the third and fourth toes, explored by MLPA, showing the same associated microduplications, 15q and Xq, without a concurrent deletion.

Submicroscopic subtelomeric aberrations in Chinese patients with unexplained developmental delay/mental retardation

BACKGROUND

Subtelomeric imbalance is widely accepted as related to developmental delay/mental retardation (DD/MR). Fine mapping of aberrations in gene-enriched subtelomeric regions provides essential clues for localizing critical regions, and provides a strategy for identifying new candidate genes. To date, no large-scale study has been conducted on subtelomeric aberrations in DD/MR patients in mainland China.

METHODS

This study included 451 Chinese children with moderate to severe clinically unexplained DD/MR. The subtelomere-MLPA (multiplex ligation dependent probe amplification) and Affymetrix human SNP array 6.0 were used to determine the subtelomeric copy number variations. The exact size and the breakpoint of each identified aberration were well defined.

RESULTS

The submicroscopic subtelomeric aberrations were identified in 23 patients, with a detection rate of 5.1%. 16 patients had simple deletions, 2 had simple duplications and 5 with both deletions and duplications. The deletions involved 14 different subtelomeric regions (1p, 2p, 4p, 6p, 7p, 7q, 8p, 9p, 10p, 11q, 14q, 15q, 16p and 22q), and duplications involved 7 subtelomeric regions (3q, 4p, 6q, 7p, 8p, 12p and 22q). Of all the subtelomeric aberrations found in Chinese subjects, the most common was 4p16.3 deletion. The sizes of the deletions varied from 0.6 Mb to 12 Mb, with 5-143 genes inside. Duplicated regions were 0.26 Mb to 11 Mb, with 6-202 genes inside. In this study, four deleted subtelomeric regions and one duplicated region were smaller than any other previously reported, specifically the deletions in 11q25, 8p23.3, 7q36.3, 14q32.33, and the duplication in 22q13. Candidate genes inside each region were proposed.

CONCLUSIONS

Submicroscopic subtelomeric aberrations were detected in 5.1% of Chinese children with clinically unexplained DD/MR. Four deleted subtelomeric regions and one duplicated region found in this study were smaller than any previously reported, which will be helpful for further defining the candidate dosage sensitive gene associated with DD/MR.

Use of Multiplex Ligation-Dependent Probe Amplification (MLPA) in screening of subtelomeric regions in children with idiopathic mental retardation

OBJECTIVE

To detect subtelomeric copy number variations (deletions and duplications) using Multiplex Ligation-Dependent Probe Amplification (MLPA) technique in children with idiopathic mental retardation.

METHODS

All children presenting to the genetics out-patient department for evaluation of mental retardation or developmental delay over a period of two years, for whom no identifiable cause could be found by clinical evaluation, karyotyping, neuroimaging and other relevant investigations.

RESULTS

In the present study, two cases deletions and one case of duplication were detected amongst 65 cases with idiopathic mental retardation/ global developmental delay. The overall detection rate is 4.6%. The detection rate is higher (13%) in children with facial dysmorphism.

CONCLUSION

MLPA for subtelomeric regions is recommended for evaluation of children with idiopathic mental retardation/ global developmental delay were included in the study.

MLPA subtelomere analysis in Tunisian mentally retarded patients

Subtelomeric rearrangements significantly contribute to idiopathic mental retardation and result in several mental retardation syndromes; however, most subtelomeric defects lack a characteristic phenotype. Thirty patients with unexplained mental retardation, a normal R banded karyotype at the 550 band, and no clinically recognizable syndrome were screened by Multiplex ligation-dependent probe amplification (MLPA). Four anomalies were identified: deletion 17q, duplications (4q), and associated duplications 15q and Xq. This duplication was found in two sisters of the proband. Anomalies were unidentified by the conventional technique. The prevalence of subtelomeric imbalances in our cohort of moderate to severe mental retardation is around 13% and is consistent with the literature. The sensitivity of the MLPA technique was characterized on cytogenetically verified positive and negative controls. MLPA is a fast, reliable, and relatively inexpensive technique to detect subtelomeric rearrangement in comparison with the fluorescence in situ hybridization (FISH) technique.

16p subtelomeric duplication: a clinically recognizable syndrome

We report on two patients with duplication of the subterminal region of chromosome 16p (dup16p) recognized by fluorescent in situ hybridization (FISH) telomere analysis, presenting with closely overlapping facial features and neurological impairment. Distinct facial anomalies included high forehead, sparse eyebrows, blepharophimosis, short nose, everted upper lip, high-arched palate, wide-spaced teeth, and cupped anteverted ears. Susceptibility to vascular anomalies, in particular pulmonary hypertension and portal cavernoma, was found in one patient. Subtelomeric analysis by FISH demonstrated a de novo duplication of the subtelomeric region of chromosome 16p and a deletion of the subtelomeric region of chromosome 4q in case 1, and duplication of the subtelomeric region of 16p and a deletion of the subtelomeric region of 21q, resulting from malsegregation of a balanced maternal traslocation t(16pter;21qter) in case 2. The extension of duplicated regions measured by array-comparative genome hybridization was about 12 Mb on 16p13.3p13.13 in case 1, and about 8.5 Mb on 16p13.3p13.2 in case 2. In conclusion, we reported a clinically recognizable disorder in two patients with dup16p. Pulmonary hypertension, vascular ring, and manifestations of vascular disruption, as terminal hypoplasia of hands and aplasia cutis, have been previously described in association with dup16p. Thus, susceptibility to pulmonary vascular disease and other vascular anomalies can be a feature of dup16p, suggesting that this subtelomeric region in some respect could be related to vascular anomalies.