Atypical 22q11.2 deletion in a patient with DGS/VCFS spectrum

Deletions in region 22q11.2 usually occur between two low copy repeat regions (LCRs), which are preferred chromosome sites for rearrangements. Most of the deletions encompass the same 3 or 1.5 Mb region, with breakpoints at LCR A and D or at LCR A and B, respectively. We report on a patient with clinical features of the 22q deletion syndrome who presents a novel, atypical deletion, smaller than 1.5 Mb, with distal breakpoint in LCR B and proximal breakpoint within no known LCR site.     

Atypical deletion of 22q11.2: Detection using the FISH TBX1 probe and molecular characterization with high-density SNP arrays

Despite the heterogeneous clinical presentations, the majority of patients with 22q11.2 deletion syndrome (22q11.2 DS) have either a common recurrent 3 Mb deletion or a less common, 1.5 Mb nested deletion, with breakpoint sites in flanking low-copy repeats (LCR) sequences. Only a small number of atypical deletions have been reported and precisely defined. Haploinsufficiency of the TBX1 gene was determined to be the likely cause of 22q11.2 DS. The diagnostic procedure usually used is FISH using commercially probes (N25 or TUPLE1). However, this test does not contain TBX1, and fails to detect deletions that are either proximal or distal to the FISH probes. Here, we report on two patients with clinical features suggestive of 22q11.2 DS, a male infant with facial dysmorphia, pulmonary atresia, ventricular septal defect, neonatal hypocalcemia, and his affected mother, with facial dysmorphia, learning disabilities, and hypernasal speech. They were tested negative for 22q11.2 DS using N25 or TUPLE1 probes, but were shown deleted for a probe containing TBX1. Delineation of the deletion was performed using high-density SNP arrays (Illumina, 370K). This atypical deletion was spanning 1.89 Mb. The distal breakpoint resided in LCR-D, sharing the same distal breakpoint with the 3 Mb common deletion. The proximal breakpoint was located 105 kb telomeric to TUPLE1, representing a new breakpoint variant that does not correspond to known LCRs of 22q11.2. We conclude that FISH with the TBX1 probe is an accurate diagnostic tool for 22q11.2 DS, with a higher sensitivity than FISH using standard probes, detecting all but the rarest deletions, greatly reducing the false negative rate.     

Homozygous 22q11.2 distal type II microdeletion is associated with syndromic neurodevelopmental delay

Genomic disorders result from heterozygous copy number variants (CNVs). Homozygous deletions spanning numerous genes are rare, despite the potential contribution of consanguinity to such instances. CNVs in the 22q11.2 region are mediated by nonallelic homologous recombination between pairs of low copy repeats (LCRs), from amongst eight LCRs designated A-H. Heterozygous distal type II deletions (LCR-E to LCR-F) have incomplete penetrance and variable expressivity, and can lead to neurodevelopmental issues, minor craniofacial anomalies, and congenital abnormalities. We report siblings with global developmental delay, hypotonia, minor craniofacial anomalies, ocular abnormalities, and minor skeletal issues, in whom chromosomal microarray identified a homozygous distal type II deletion. The deletion was brought to homozygosity as a result of a consanguineous marriage between two heterozygous carriers of the deletion. The phenotype of the children was strikingly more severe and complex than that of the parents. This report suggests that the distal type II deletion harbors a dosage-sensitive gene or regulatory element, which leads to a more severe phenotype when deleted on both chromosomes.     

Distal deletion at 22q11.2 as differential diagnosis in Craniofacial Microsomia: Case report and literature review

Craniofacial Microsomia (CFM) also known as Oculo-auriculo-vertebral Spectrum (OAVS) or Goldenhar Syndrome, presents wide phenotypic and etiological heterogeneity. It affects mainly the structures originated from the first and second pharyngeal arches. In addition, other major anomalies may also be found, including congenital heart diseases. In this study, we report a patient with distal deletion in the 22q11.2 region and a phenotype which resembles CFM. The proband is a girl, who presented bilateral preauricular tags, left auditory canal stenosis, malar hypoplasia, cleft lip and palate, mild asymmetry of soft tissue in face, congenital heart disease, intestinal atresia, annular pancreas and hydronephrosis. The genomic imbalances investigation by Multiplex Ligation-dependent Probe Amplification (MLPA) and Chromosomal Microarray Analysis (CMA) revealed a distal deletion of 1,048?kb?at 22q11.2 encompassing the region from Low Copy Repeats (LCRs) D to E. We did review of the literature and genotype-phenotype correlation. This is the sixth case of distal 22q11.2 deletion resembling CFM and the second encompassing the region between LCRs D to E. All cases share some phenotypic signs, such as preauricular tags, facial asymmetry, cleft lip and palate, and congenital heart diseases. Candidate genes in this region have been studied by having an important role in pharyngeal arches developmental and in congenital heart diseases, such as HIC2, YPEL1and MAPK1/ERK2. This case corroborates the phenotypic similarity between 22q11.2 distal deletion and CFM/OAVS. It also contributes to genotype-phenotype correlation and reinforces that candidate genes for CFM, in the 22q11.2 region, might be located between LCRs D and E.     

Phenotypic heterogeneity in a family with a small atypical microduplication of chromosome 22q11.2 involving TBX1

The chromosome 22q11.2 region is commonly involved in non-allelic homologous recombination (NAHR) events. Microduplications of 22q11.2, usually involving a 3 Mb or 1.5 Mb region constitute the 22q11 microduplication syndrome. Both microdeletions and microduplications of 22q11.21 are reported to share several phenotypic characteristics, including dysmorphic facial features, velopharyngeal insufficiency, congenital heart disease, urogenital abnormalities, and immunologic defects. We report a child who presented at 8 months of age for evaluation of microcephaly and mild motor delay. Head circumference at birth, at 8 months, and at 19 months of age was below the 3rd centile. Other findings included left-sided cryptorchidism and developmental dysplasia of the left hip. In addition, echocardiography revealed a restrictive patent ductus arteriosus. Chromosomal microarray analysis using Affymetrix Genome-Wide Human SNP Array 6.0 revealed a novel 437 kb interstitial duplication at 22q11.21, involving TBX1, whose breakpoints did not coincide with known low copy repeat (LCR) regions. The same duplication was confirmed by fluorescent in situ hybridization (FISH) in the patient's mother and an older sister. The mother has a history of anxiety disorder and depression. The sister had a history of delayed motor milestones. None of the three duplication carriers has any documented renal anomalies or other significant medical problems. This report demonstrates the clinical heterogeneity associated with microduplications of 22q11.2 and illustrates the difficulties related to providing prognostic information and accurate genetic counseling to families when this finding is detected. The described microduplication is the smallest in this genomic region reported to date and further implicates abnormal gene dosage of TBX1 in disorders resulting from 22q11.2 rearrangements.     

1.5 Mb de novo 22q11.21 microduplication in a patient with cognitive deficits and dysmorphic facial features

The 22q11.2 microduplication syndrome is caused by non-allelic homologous recombination mediated by misalignments of low copy repeats located in the region deleted in the DiGeorge syndrome (DGS)/velocardiofacial syndrome (VCFS). The variable phenotype of such condition, consisting in a combination of dysmorphic facial features, cognitive deficits, velopharyngeal insufficiency, congenital heart defects and immunologic derangement, is caused usually in 90% of cases by a 3 Mb deletion or in a minority of cases (7%) by a 1.5 Mb deletion. The most common reciprocal event of deletion is the 3 Mb duplication, reported more recently with a variable phenotype, ranging from multiple defects to normality. In this study, we report a 2.5-year-old girl with cognitive deficits and dysmorphic facial features such as superior placement of eyebrows, upslanting palpebral fissures, widely spaced eyes, broad nasal bridge and epicanthal folds. Fluorescent in situ hybridization for DGS/VCFS region on metaphase chromosomes did not show any apparent anomaly. Subsequent array comparative genomic hybridization study, confirmed by multiplex ligation-dependent probe assay and microsatellite analysis, disclosed a 1.5 Mb de novo 22q11.21 duplication concerning the same chromosomal region deleted in a minority of patients with DGS. These findings identify the minimal duplicated region leading to this emerging syndrome.     

Prenatal and postnatal diagnosis of 22q11.2 deletion syndrome

Microdeletion of chromosome 22q11.2, the most common human deletion syndrome encompasses a wide spectrum of abnormalities. Many clinical or ultrasonographic findings may support deletion studies, either in utero or in the post-natal period. The objective of our study was to evaluate the circumstances of 22q11.2 deletion diagnosis in a single centre of genetics during a 12 years period. Testing for 22q11.2 deletion was performed in 883 cases. Congenital heart defect was the most common reason for referral. An antenatal 22q11.2 microdeletion was detected in 8 fetuses (4.7%) among 169 pregnancies, all presenting conotruncal anomalies. In one case prenatal diagnosis led to the identification of the deletion in the mildly affected father and had negative impact on the family. During the same period, postnatal 22q11.2 DS was diagnosed in 81 out of 714 patients aged from birth to 42 years (11.3%) (p = 0.02). A CHD was present in 37 (45.7%). This figure is significantly lower than the 75% commonly reported. These results suggest that deletion studies could be justifiable in fetuses with non-cardiac prenatal sonographic findings that have been reported in association with 22q11.2 DS. However, as most of these malformations are rather common and non specific, systematic 22q11.2 testing is not justifiable. In such cases, careful cardiac and thymus examination could provide additional clues for 22q11.2 testing. In addition parents should be given accurate information before antenatal or postnatal testing, including the wide variability of the clinical phenotype, the impossibility to establish a precise prognosis concerning psychomotor development and psychiatric risks.     

A patient with a de novo distal 22q11.2 microdeletion and anxiety disorder

We report on a young female with normal intelligence evaluated for long‐term anxiety. Her history includes prematurity, neonatal feeding problems, surgical correction of congenital heart defects, recurrent upper airway and urinary tract infections, and delayed motor and developmental milestones. Physical examination disclosed small stature and minor dysmorphisms. Chromosome analysis, 22q11.2 FISH analysis, and subtelomeric MLPA testing did not detect any abnormalities. Genome wide SNP Array analysis showed a de novo deletion in 22q11.21q11.22, the so‐called distal 22q11 microdeletion that involves the MAPK1 gene. A diagnosis of panic disorder was made and the patient was successfully treated with a daily dose of 20 mg citalopram. To our knowledge, this is the first adolescent patient with a long history of complaints about anxiety and a distal 22q11 microdeletion. We speculate that genes from the deleted region, especially MAPK1, increase the neurobiological susceptibility to anxiety disorders that may be a part of the psychopathological phenotype of the distal 22q11.2 microdeletion syndrome. © 2010 Wiley‐Liss, Inc.     

Further evidence of GABRA4 and TOP3B as autism susceptibility genes

Chromosomal copy number variants (CNVs) are known contributors to neurodevelopmental conditions such as autism spectrum disorder (ASD). Both array comparative genomic hybridization and next-generation sequencing techniques have led to an increased detection of small CNVs and the identification of many candidate susceptibility genes for ASD. We report familial inheritance of two CNVs that include genes with known involvement in neurodevelopment. These CNVs are found in various combinations among four siblings with autism spectrum disorder, as well as in their neurodevelopmentally normal parents. We describe a 2.4 Mb duplication of 4p12 to 4p11 that includes GABRA4 (OMIM: 137141) and other GABA receptor genes, as well as a 246 kb deletion at 22q11.22 involving the TOP3B gene (OMIM: 603582). The maternally inherited 4p duplication was detected in three siblings, two of whom also had the paternally inherited 22q11.22 deletion. The fourth sibling only had the 22q11.22 deletion. These CNVs have rarely been reported in the literature. Upon review, a single publication was found describing a similar 4p duplication in three generations of a family with neurodevelopmental and neuropsychiatric disorders, as well as in an unrelated patient with autism (Polan et al., 2014). TOP3B falls within the distal 22q11.22 microdeletion syndrome and has been associated with schizophrenia, neurodevelopmental disorders including epilepsy, and cardiac defects. The identification of this family contributes to the understanding of specific genetic contributors to neurodevelopmental disorders and an emerging phenotype associated with proximal 4p duplication.     

人类染色体22q11.2微缺失综合征发病机制的研究进展

22q11缺失综合征（22qll deletion syndrome,22qllDS）是由染色22q11．21-q11．23缺失引起的遗传性综合征，其临床表现复杂，主要包括心脏、颅面、免疫等系统异常。22qll缺失产生的机制是缺失区域内低拷贝重复序列（10w-copy-repetitives，LCR22s）之间的不对称重组。本文对其临床表现、发病机制、候选基因克隆等方面的近年进展进行了综述。     

Diagnosis of distal 22q11.2 deletion syndrome in a patient with a teratoid/rhabdoid tumour

We report an 18 year old patient with mild intellectual disability who was diagnosed with a late onset teratoid/rhabdoid tumour by histological and immunohistochemical studies. Array-CGH studies, performed on a peripheral blood sample, showed a 3.4Mb deletion of chromosome 22q11.2, distal to the common DiGeorge syndrome (DGS) or Velocardiofacial syndrome (VCFs) region. This deletion is consistent with a diagnosis of distal 22q11.2 deletion syndrome. The deletion encompasses the INI1/SMARCB1 tumour suppressor gene. Biallelic inactivation of this gene is characteristic of atypical teratoid/rhabdoid tumours. Although several constitutional chromosome conditions are known to have increased susceptibility to various forms of cancer, very little is known regarding the magnitude of risk for malignancy associated with distal 22q11.2 deletion syndrome. In view of this finding we suggest that patients diagnosed with distal 22q11.2 deletion syndrome undergo careful prolonged monitoring for this type of tumour. This case demonstrates the need to carefully assess regions found to be deleted in individuals, referred for dysmorphia and/or developments delay, by array-CGH for the presence of genes known to be implicated in malignancy.     

Under-recognition of 22q11.2 deletion in adult Chinese patients with conotruncal anomalies: Implications in transitional care

22q11.2 deletion syndrome (22q11.2DS) is a multi-systemic disorder with high phenotypic variability. Under-diagnosis in adults is common and recognition of facial dysmorphic features can be affected by age and ethnicity. This study aims to determine the prevalence of undiagnosed 22q11.2DS in adult Chinese patients with conotruncal anomalies and to delineate their facial dysmorphisms and extra-cardiac manifestations. We recruited consecutively 156 patients with conotruncal anomalies in an adult congenital heart disease (CHD) clinic in Hong Kong and screened for 22q11.2DS using fluorescence-PCR and fluorescence in-situ hybridization. Assessment for dysmorphic features was performed by a cardiologist at initial screening and then by a clinical geneticist upon result disclosure. Clinical photographs were taken and childhood photographs collected. Eighteen patients (11.5%) were diagnosed with 22q11.2DS, translating into 1 previously unrecognized diagnosis of 22q11.2DS in every 10 adult patients with conotruncal anomalies. While dysmorphic features were detected by our clinical geneticist in all patients, only two-thirds were considered dysmorphic by our cardiologist upon first assessment. Evolution of facial dysmorphic features was noted with age. Extra-cardiac manifestations included velopharyngeal incompetence or cleft palate (44%), hypocalcemia (39%), neurodevelopmental anomalies (33%), thrombocytopenia (28%), psychiatric disorders (17%), epilepsy (17%) and hearing loss (17%). We conclude that under-diagnosis of 22q11.2DS in Chinese adults with conotruncal defects is common and facial dysmorphic features may not be reliably recognized in the setting of adult CHD clinic, referral for genetic evaluation and molecular testing for 22q11.2DS should be offered to patients with conotruncal defects.     

人类染色体22q11.2微缺失综合征发病机制的研究进展

22ql1缺失综合征(22q11 deletion syndrome,22q11DS)是由染色22ql1.21-ql1.23缺失引起的遗传性综合征，其临床表现复杂，主要包括心脏、颅面、免疫等系统异常。22q11缺失产生的机制是缺失区域内低拷贝重复序列(1ow-copy-repetitives，LCR22s)之间的不对称重组。本文对其临床表现、发病机制、候选基因克隆等方面的近年进展进行了综述。     

Manifestation of recessive combined D‐2‐, L‐2‐hydroxyglutaric aciduria in combination with 22q11.2 deletion syndrome

22q11.2 deletion syndrome is one of the most common human microdeletion syndromes. The clinical phenotype of 22q11.2 deletion syndrome is variable, ranging from mild to life‐threatening symptoms, depending mainly on the extent of the deleted region. Brain malformations described in association with 22q11.2 deletion syndrome include polymicrogyria, cerebellar hypoplasia, megacisterna magna, and agenesis of the corpus callosum (ACC), although these are rare. We report here for the first time a patient who manifested combined D‐2‐ and L‐2‐hydroxyglutaric aciduria as a result of a hemizygous mutation in SLC25A1 in combination with 22q11.2 deletion. The girl was diagnosed to have ACC shortly after birth and a deletion of 22q11.2 was identified by genetic analysis. Although the patient showed cardiac anomalies, which is one of the typical symptoms of 22q11.2 deletion syndrome, her rather severe phenotype and atypical face prompted us to search for additional pathogenic mutations. Three genes present in the deleted 22q11.2 region, SLC25A1, TUBA8, and SNAP29, which have been reported to be associated with brain malformation, were analyzed for the presence of pathogenic mutations. A frameshift mutation, c.18_24dup (p.Ala9Profs*82), was identified in the first exon of the remaining SLC25A1 allele, resulting in the complete loss of normal SLC25A1 function in the patient's cells. Our results support the notion that the existence of another genetic abnormality involving the retained allele on 22q11.2 should be considered when atypical or rare phenotypes are observed.

     

Exploring the potential association among sleep disturbances,cognitive impairments,and immune activation in 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.DS) is a neurogenetic disorder caused by a microdeletion in chromosome 22. Its phenotype includes high rates of psychiatric disorders, immune system abnormalities, and cognitive impairments. We assessed the quality of sleep in 22q11.2DS and its potential link to inflammatory markers and cognitive deficits. Thirty‐three 22q11.2DS individuals and 24 healthy controls were studied. Sleep parameters were assessed by the Pittsburgh sleep quality index (PSQI) questionnaire and correlated with serum cytokine levels and cognitive functioning, measured using the Penn computerized neurocognitive battery (CNB). The 22q11.2DS individuals had significantly worse sleep quality scores than the controls, unrelated to the psychiatric or physical comorbidities common to 22q11.2DS. Interleukin 6 levels were correlated with the overall score of the PSQI questionnaire for nonpsychotic 22q11.2DS participants only. Several domains of the CNB were associated with poorer sleep quality, suggesting that cognitive impairments in 22q11.2DS may be at least partially explained by poor sleep quality. Our findings confirm sleep impairments in individuals with 22q11.2DS, which might negatively affect their cognitive functioning, and corroborate a potential role of immunological pathways in the 22q11.2DS neuro‐phenotype.     

Genotypic and phenotypic variability of 22q11.2 microduplications: An institutional experience

Duplications in the 22q11.2 region can cause 22q11.2 duplication syndrome and encompass a variety of phenotypes including developmental delays, facial abnormalities, cardiovascular defects, central nervous system delays, and other congenital abnormalities. However, the contribution of these contiguous duplicated regions to the clinical phenotypes has not been fully elucidated. In this study, we identified nine patients carrying different 22q11.2 microduplications detected by chromosomal microarray. Of these patients, seven pediatric patients presented with various clinical features including two neonate cases died shortly after birth, and two healthy adults. We examined region specific genotype–phenotype associations and found unpredictability associated with 22q11.2 duplications in these nine patients.     

Medical,welfare, and educational challenges and psychological distress in parents caring for an individual with 22q11.2 deletion syndrome: A cross-sectional survey in Japan

Parents of children with 22q11.2 deletion syndrome (22q11DS) experience distress not only due to multimorbidity in the patients, but also due to professionals' lack of understanding about 22q11DS and insufficient support systems. This study investigated relationships between medical, welfare, and educational challenges and parental psychological distress. A cross-sectional survey was conducted on primary caregivers of children with 22q11DS. Participants included 125 parents (114 mothers, 91.2%; average age = 44.3 years) who reported their challenges, psychological distress, and child's comorbidities of 22q11DS. Results showed that the difficulty in going to multiple medical institutions (β = 0.181, p < 0.05) and lack of understanding by welfare staff and insufficient welfare support systems for 22q11DS (β = 0.220–0.316, all p < 0.05) were associated with parental psychological distress, even after adjusting for child's comorbidities. In the subsample of parents whose child attended an educational institution, inadequate management in classroom and mismatch between service and users in educational settings were associated with psychological distress (β = 0.222–0.296, all p < 0.05). This study reveals the importance of assessing not only severity of comorbidities in 22q11DS, but also the medical, welfare, and educational challenges for parental mental health.     

Anomalies of the genitourinary tract in children with 22q11.2 deletion syndrome

The 22q11.2 deletion syndrome (22q11.2DS) involves multiple organ systems with variable phenotypic expression. Genitourinary tract abnormalities have been noted to be present in up to 30–40% of patients. At our institution, an internationally recognized, comprehensive, and multidisciplinary 22q11.2DS care center has been providing care to these children. We sought to report on the incidence of genitourinary tract anomalies in this large cohort and, therefore, retrospectively reviewed all patients who underwent a complete evaluation from 1992 to March 2017. We identified all children with any genital or urinary tract anomaly. For all children with a diagnosis of hydronephrosis, the underlying etiology was determined, when possible. Overall, 1,073 of 1,267 children with 22q11.2DS underwent renal evaluations at our institution. Hundered Sixty‐Two (15.1%) children had structural abnormalities of their kidneys/urinary tracts. The majority of children with hydronephrosis (63%) had isolated upper tract dilation without any additional diagnoses. Boys were significantly more likely to be diagnosed with a genital abnormality than girls (7.7 vs. 0.5%, p < 0.001). Of the 649 boys in the entire cohort, 24 (3.7%) had cryptorchidism and 24 (3.7%) had hypospadias, which was noted to be mild in all except one boy. Overall, findings of hydronephrosis, unilateral renal agenesis, and multicystic dysplastic kidney occur at higher rates than expected in the general population. Given these findings, in addition to routine physical examination, we believe that all patients with 22q11.2DS warrant screening RBUS at time of diagnosis.     

Recurrent 22q11.2 deletion in a sibship suggestive of parental germline mosaicism in velocardiofacial syndrome

Deletions of chromosome 22q11.2 are recognized as the main cause of a number of clinical phenotypes, including velocardiofacial syndrome (VCFS) and DiGeorge syndrome (DGS). Velocardiofacial syndrome is a relatively common developmental disorder that is characterized by craniofacial anomalies and conotruncal heart defects. Most 22q11.2 deletions occur sporadically, although the deletion may be transmitted in some cases. The present performed a molecular analysis in one family including a patient with clinical diagnosis of VCFS and his sister with a suggestive phenotype. Six polymorphic 22q11.2 markers (i.e. D22S420, D22S264, D22S941, D22S306, D22S425 and D22S257) were used for genotype analysis of the DNA from the patients and unaffected relatives. The results revealed a 22q11.2 deletion in the patient and his sister from one of six markers (i.e. D22S941). Genotype analysis demonstrated that the deletion in this sib was of maternal origin. The results suggest that the mother probably has gonadal mosaicism. The other relatives present normal DNA profiles for all markers. These results have implications for genetic counseling because of a risk of transmission by germ cells carrying the deletion, even when parents present with a normal DNA profile in their blood cells.