Phenotype of adults with the 22q11 deletion syndrome: A review

Thalamocortical organoids enable in vitro modeling of 22q11.2 microdeletion associated with neuropsychiatric disorders

Thalamic dysfunction has been implicated in multiple psychiatric disorders. We sought to study the mechanisms by which abnormalities emerge in the context of the 22q11.2 microdeletion, which confers significant genetic risk for psychiatric disorders. We investigated early stages of human thalamus development using human pluripotent stem cell-derived organoids and show that the 22q11.2 microdeletion underlies widespread transcriptional dysregulation associated with psychiatric disorders in thalamic neurons and glia, including elevated expression of FOXP2. Using an organoid co-culture model, we demonstrate that the 22q11.2 microdeletion mediates an overgrowth of thalamic axons in a FOXP2-dependent manner. Finally, we identify ROBO2 as a candidate molecular mediator of the effects of FOXP2 overexpression on thalamic axon overgrowth. Together, our study suggests that early steps in thalamic development are dysregulated in a model of genetic risk for schizophrenia and contribute to neural phenotypes in 22q11.2 deletion syndrome.

Evaluation and Maintenance of Behavioral Interventions for 22q11.2 Deletion Syndrome

22q11.2-deletion syndrome is a genetic disorder caused by a small deletion of chromosome 22. This deletion often results in developmental delays, learning disabilities, medical conditions, and comorbid psychiatric conditions. Patients with 22q11.2DS may present with a variety of behavioral phenotypes including obsessiveness and rigidity, poor social skills, and anxiety. In some cases, the phenotype can consist of destructive and inappropriate behavior including harming self and others. Behavioral difficulties are reported as one of the most challenging aspects of 22q11.2-deletion syndrome for families of patients, however, few studies have examined behavioral interventions as a possible therapeutic treatment for this population. Using principles derived from operant-behavioral psychology, we conducted functional assessments to determine the environmental correlates of destructive and inappropriate behaviors in two adult men with 22q11.2-deletion syndrome. Subsequently, behavioral interventions based on differential reinforcement were incorporated into each participant's natural environment to eliminate these behaviors. Significant reductions in destructive and inappropriate behavior were observed with both participants and therapeutic gains were maintained at follow-up. We discuss the role of behavioral interventions in combination with appropriate psychotropic medication when addressing challenging behaviors in this population.

DiGeorge syndrome: consider the diagnosis

DiGeorge syndrome (DGS) is caused by a chromosomal microdeletion at 22q11.2 that results in impaired development of the pharyngeal pouch system. Patients with DGS may have developmental abnormalities of craniofacial structures, parathyroid glands, thymus and cardiac outflow tract. Doctors have been routinely testing for DGS in newborns with conotruncal cardiac anomalies since the late 1990s; before then, however, they relied on complex diagnostic criteria and the disease was often missed. Adults born with conotruncal defects before the late 1990s may have undiagnosed DGS. We present one such case: a 35-year-old woman with a cardiac diagnosis of tetralogy of Fallot and unilateral absence of a pulmonary arter who was found to have DGS. Identifying DGS in adults is important both for disease management and genetic counselling. Our case emphasises the importance of screening for DGS in adults who were born with conotruncal cardiac abnormalities before widespread neonatal testing became common.

Functional Dysconnectivity in Ventral Striatocortical Systems in 22q11.2 Deletion Syndrome

22q11.2 deletion syndrome (22q11.2DS) is a genetic neurodevelopmental disorder that represents one of the greatest known risk factors for psychosis. Previous studies in psychotic subjects without the deletion have identified a dopaminergic dysfunction in striatal regions, and dysconnectivity of striatocortical systems, as an important mechanism in the emergence of psychosis. Here, we used resting-state functional MRI to examine striatocortical functional connectivity in 22q11.2DS patients. We used a 2 × 2 factorial design including 125 subjects (55 healthy controls, 28 22q11.2DS patients without a history of psychosis, 10 22q11.2DS patients with a history of psychosis, and 32 subjects with a history of psychosis without the deletion), allowing us to identify network effects related to the deletion and to the presence of psychosis. In line with previous results from psychotic patients without 22q11.2DS, we found that there was a dorsal to ventral gradient of hypo- to hyperstriatocortical connectivity related to psychosis across both patient groups. The 22q11.2DS was additionally associated with abnormal functional connectivity in ventral striatocortical networks, with no significant differences identified in the dorsal system. Abnormalities in the ventral striatocortical system observed in these individuals with high genetic risk to psychosis may thus reflect a marker of illness risk.

A Rare Etiology of Hypocalcemic Seizures in Adulthood: Clues to Diagnosis from Facial Dysmorphism

We report a 40-year-old male who presented with seizures due to hypocalcemia. Biochemical evaluation revealed the diagnosis of hypoparathyroidism. The symptom complex of dysmorphic facies and intellectual disability along with hypoparathyroidism led to a suspicion of 22q11.2 microdeletion syndrome (22q11.2DS), which was confirmed by multiplex ligation-dependent probe amplification (MLPA) analysis showing 22q11.2.21 microdeletion.

Palatoschisis, Schizophrenia and Hypocalcaemia: Phenotypic Expression of 22q11.2 Deletion Syndrome (DiGeorge Syndrome) in an Adult

22q11.2 deletion syndrome typically presents with congenital cardiac anomalies, immunodeficiencies and hypoparathyroidism. However, clinical findings vary greatly. We present the case of a 56-year-old man, with a history of cleft palate and schizophrenia, who was newly diagnosed with 22q11.2 deletion syndrome during an episode of hypocalcaemia. The syndrome is caused by developmental abnormalities of the embryonic pharyngeal arch system. Treatment of hypocalcaemia with oral calcium and vitamin D is usually sufficient.

LEARNING POINTS

22q11.2 deletion syndrome typically presents with congenital cardiac anomalies, immunodeficiencies and hypoparathyroidism.The syndrome has a variable phenotypic expression and can therefore remain unrecognised in adult patients with mild symptoms.22q11.2 deletion syndrome should be borne in mind, particularly as regards adult psychiatric patients.

Access to Multidisciplinary Care for Patients With 22q11.2 Deletion Syndrome: Identifying Breakdowns in the Screening Process

The 22q11.2 deletion syndrome affects approximately 1 in 4000 live births and involves cardiac defects, immunodeficiency, and endocrine disruption. The complexity of diagnosis and multifaceted care often leads to fragmented management in the short and long term. With the purpose of developing an effective multidisciplinary program, the authors aimed to identify the deficiencies in current screening and referral processes among the teams required in the care for patients with 22q11.2 deletion syndrome. A retrospective chart review was conducted at our institution between 2001 and 2016. Patients with confirmed 22q11.2 deletion diagnoses between the ages of 0 and 28 were included. A list of 15 relevant specialties that should evaluate patients with 22q11.2 deletion syndrome was created according to established guidelines. Patient medical and demographic information were collected and analyzed. A total of 270 patients were included. Mean age at diagnosis was 3.3 years. On average, patients visited 6 of 15 departments (1-14). Only 8.8% of patients visited >10 specialties. The majority were seen by Cardiology, Allergy and Immunology, Genetics, and Speech (57.4-87.8%). A minority were seen by Hematology and Oncology, Sleep Therapy, and Physical Therapy (13.3-16.3%). Only 34.1% encountered plastic surgery. Negative correlation (-0.128; P = 0.035) was demonstrated between patients' age at diagnosis and number of specialty teams encountered. This study highlights the current underutilization of services required to manage patients with 22q11.2 deletion syndrome. While screening guidelines have been established, implementation can be challenging as it requires efficient care coordination between teams. Moving forward, the authors believe that a multidisciplinary clinical approach to streamline patient care is necessary.

Ontogeny of the facial phenotypic variability in Mexican patients with 22q11.2 deletion syndrome

Background

22q11.2 deletion syndrome is a medical condition that results from genomic loss at chromosome 22. Affected patients exhibit large variability that ranges from a severe condition to mild symptoms. In addition, the spectrum of clinical features differs among populations and even within family members. The facial features related to this syndrome are not an exception, and although part of its variation arises through development, few studies address this topic in order to understand the intra and inter-population heterogeneities. Here, we analyze the ontogenetic dynamics of facial morphology of Mexican patients with del22q11.2 syndrome.

Methods

Frontal facial photographs of 37 patients (mean age = 7.65 ± 4.21 SE) with del22q11.2DS and 200 control subjects (mean age = 7.69 ± 4.26 SE) were analyzed using geometric morphometric methods. Overall mean shape and size differences between patients and controls were analyzed, as well as differences in ontogenetic trajectories (i.e. development, growth, and allometry).

Results

We found that Mexican patients show typical traits that have been reported for the Caucasian population. Additionally, there were significant differences between groups in the facial shape and size when all the ontogenetic stages were considered together and, along ontogeny. The developmental and allometric trajectories of patients and controls were similar, but they differed in allometric scaling. Finally, patients and controls showed different growth trajectories.

Conclusion

The results suggest that the typical face of patients with del22q11.2DS is established prenatally; nonetheless, the postnatal ontogeny could influence the dysmorphology and its variability through size-related changes.

Infertility in a man with oligoasthenozoospermia associated with mosaic chromosome 22q11 deletion

BACKGROUND

A 30-year-old oligoasthenozoospermia man was found to have unbalance mosaic translocation between chromosome 22 and four other chromosomes (5, 6, 13, and 15) during the investigations for a couple with infertility for 3 years, which is a rare event in human pathology.

METHODS

Classical cytogenetics analysis, fluorescence in situ hybridization (FISH), and chromosome microarray analyses (CMA) were performed on peripheral blood lymphocytes; copy number variation sequencing (CNV-Seq) analysis was performed on sperm DNA.

RESULTS

Classical cytogenetics analysis showed the presence of six cell lines on peripheral blood lymphocytes: 45, XY, der (13) t(13;22),-22[10]/46, XY, t(13;22)[6]/45, XY, der(15)t(15;22),-22[4]/46, XY, t(13;22)[1]/45, XY, der(5)t(5;22),-22[1]/45, XY, der(6)t(6;22)[1]. FISH and CMA performed on peripheral blood cells showed the presence of a 6.9 Mb mosaic 22q11 deletion (approximately 50% of cells); it is unexpected that the phenotypes of this man were merely oligoasthenozoospermia, mild bradycardia, and mild tricuspid regurgitation. CNV-Seq analysis performed on sperm DNA revealed the rate of 22q11 deletion cells was obviously lower compared with peripheral blood cells. And the frequency of gametes exhibiting a normal or balance chromosomal equipment was above 80% in sperm samples.

CONCLUSION

To the best of our knowledge, this report is the first case of a de novo gonosomal mosaic of chromosome 22q11 deletion just associated with male infertility.

Modeling age-specific facial development in Williams-Beuren-, Noonan-, and 22q11.2 deletion syndromes in cohorts of Czech patients aged 3-18 years: A cross-sectional three-dimensional geometric morphometry analysis of their facial gestalt

Three-dimensional (3D) virtual facial models facilitate genotype-phenotype correlations and diagnostics in clinical dysmorphology. Within cross-sectional analysis of both genders we evaluated facial features in representative cohorts of Czech patients with Williams-Beuren-(WBS; 12 cases), Noonan-(NS; 14), and 22q11.2 deletion syndromes (22q11.2DS; 20) and compared their age-related developmental trajectories to 21 age, sex and ethnically matched controls in 3-18 years of age. Using geometric morphometry statistically significant differences in facial morphology were found in all cases compared to controls. The dysmorphic features observed in WBS were specific and manifested in majority of cases. During ontogenesis, dysmorphic features associated with increased facial convexity become more pronounced whereas other typical features remained relatively stable. Dysmorphic features observed in NS cases were mostly apparent during childhood and gradually diminished with age. Facial development had a similar progress as in controls, while there has been increased growth of patients' nose and chin in adulthood. Facial characteristics observed in 22q11.2DS, except for hypoplastic alae nasi, did not correspond with the standard description of its facial phenotype because of marked facial heterogeneity of this clinical entity. Because of the sensitivity of 3D facial morphometry we were able to reach statistical significance even in smaller retrospective patient cohorts, which proves its clinical utility within the routine setting.

What is new with 22q? An update from the 22q and You Center at the Children's Hospital of Philadelphia

22q11.2 deletion syndrome (22q11.2DS) is a disorder caused by recurrent, chromosome-specific, low copy repeat (LCR)-mediated copy-number losses of chromosome 22q11. The Children's Hospital of Philadelphia has been involved in the clinical care of individuals with what is now known as 22q11.2DS since our initial report of the association with DiGeorge syndrome in 1982. We reviewed the medical records on our continuously growing longitudinal cohort of 1,421 patients with molecularly confirmed 22q11.2DS from 1992 to 2018. Most individuals are Caucasian and older than 8 years. The mean age at diagnosis was 3.9 years. The majority of patients (85%) had typical LCR22A-LCR22D deletions, and only 7% of these typical deletions were inherited from a parent harboring the deletion constitutionally. However, 6% of individuals harbored other nested deletions that would not be identified by traditional 22q11.2 FISH, thus requiring an orthogonal technology to diagnose. Major medical problems included immune dysfunction or allergies (77%), palatal abnormalities (67%), congenital heart disease (64%), gastrointestinal difficulties (65%), endocrine dysfunction (>50%), scoliosis (50%), renal anomalies (16%), and airway abnormalities. Median full-scale intelligence quotient was 76, with no significant difference between individuals with and without congenital heart disease or hypocalcemia. Characteristic dysmorphic facial features were present in most individuals, but dermatoglyphic patterns of our cohort are similar to normal controls. This is the largest longitudinal study of patients with 22q11.2DS, helping to further describe the condition and aid in diagnosis and management. Further surveillance will likely elucidate additional clinically relevant findings as they age.

Congenital heart diseases and cardiovascular abnormalities in 22q11.2 deletion syndrome: From well-established knowledge to new frontiers

Congenital heart diseases (CHDs) and cardiovascular abnormalities are one of the pillars of clinical diagnosis of 22q11.2 deletion syndrome (22q11.2DS) and still represent the main cause of mortality in the affected children. In the past 30 years, much progress has been made in describing the anatomical patterns of CHD, in improving their diagnosis, medical treatment, and surgical procedures for these conditions, as well as in understanding the underlying genetic and developmental mechanisms. However, further studies are still needed to better determine the true prevalence of CHDs in 22q11.2DS, including data from prenatal studies and on the adult population, to further clarify the genetic mechanisms behind the high variability of phenotypic expression of 22q11.2DS, and to fully understand the mechanism responsible for the increased postoperative morbidity and for the premature death of these patients. Moreover, the increased life expectancy of persons with 22q11.2DS allowed the expansion of the adult population that poses new challenges for clinicians such as acquired cardiovascular problems and complexity related to multisystemic comorbidity. In this review, we provide a comprehensive review of the existing literature about 22q11.2DS in order to summarize the knowledge gained in the past years of clinical experience and research, as well as to identify the remaining gaps in comprehension of this syndrome and the possible future research directions.

Gene expression profiling in the developing secondary palate in the absence of Tbx1 function

BACKGROUND

Microdeletion of chromosome 22q11 is associated with significant developmental anomalies, including disruption of the cardiac outflow tract, thymic/parathyroid aplasia and cleft palate. Amongst the genes within this region, TBX1 is a major candidate for many of these developmental defects. Targeted deletion of Tbx1 in the mouse has provided significant insight into the function of this transcription factor during early development of the cardiac and pharyngeal systems. However, less is known about its role during palatogenesis. To assess the influence of Tbx1 function on gene expression profile within the developing palate we performed a microarray screen using total RNA isolated from the secondary palate of E13.5 mouse embryos wild type, heterozygous and mutant for Tbx1.

RESULTS

Expression-level filtering and statistical analysis revealed a total of 577 genes differentially expressed across genotypes. Data were clustered into 3 groups based on comparison between genotypes. Group A was composed of differentially expressed genes in mutant compared to wild type (n = 89); Group B included differentially expressed genes in heterozygous compared to wild type (n = 400) and Group C included differentially expressed genes in mutant compared to heterozygous (n = 88). High-throughput quantitative real-time PCR (RT-PCR) confirmed a total of 27 genes significantly changed between wild type and mutant; and 27 genes between heterozygote and mutant. Amongst these, the majority were present in both groups A and C (26 genes). Associations existed with hypertrophic cardiomyopathy, cardiac muscle contraction, dilated cardiomyopathy, focal adhesion, tight junction and calcium signalling pathways. No significant differences in gene expression were found between wild type and heterozygous palatal shelves.

CONCLUSIONS

Significant differences in gene expression profile within the secondary palate of wild type and mutant embryos is consistent with a primary role for Tbx1 during palatogenesis.

Atypical microdeletion in 22q11 deletion syndrome reveals new candidate causative genes: A case report and literature review

RATIONALE

22q11 deletion syndrome, the most common chromosomal microdeletion disease, is caused by megabase-sized deletions on chromosome 22q11.2. It is characterized by a wide spectrum of congenital anomalies in velopharyngeal and facial, cardiac, genitourinary, vertebroskeletal, respiratory, digestive, and central nervous systems. Phenotype-genotype studies have revealed several causative genes that regulate the development of the third and fourth pharyngeal arches in human. However, the exact pathogenesis of this syndrome remains unknown. Herein, we report a case of 22q11 deletion syndrome with an atypical microdeletion of 125 kb.

PATIENT CONCERNS

A 15-year-old Chinese girl presented with symptoms of facial dysmorphia, cardiac defects, velopharyngeal insufficiency, splenomegaly, immunodeficiency, and thrombocytopenia.

DIAGNOSES

Microarray analysis revealed a 22q11.23 deletion of 125 kb (chromosome 22: 24276973-24402263), suggesting the diagnosis of 22q11 deletion syndrome. The haploinsufficient genes included GSTT2B, GSTT2, DDTL, DDT, GSTTP1, LOC391322, GSTT1, and GSTTP2.

INTERVENTIONS

The patient was administrated glucocorticoids and calcium supplements.

OUTCOMES

No epistaxis or petechiae episode occurred during the follow-up; her platelet count ranged between 60 × 10 and 80 × 10/L.

LESSONS

Although none of the previous reported causative genes were affected in the patient, her clinical manifestations were typical of 22q11 deletion syndrome, apart from her progressive splenomegaly. This case indicated 8 new candidate pathogenic genes for 22q11 deletion syndrome. Given that the loss of these genes was sufficient to induce 22q11DS defects, whether these genes directly influence the pathogenesis of 22q11DS or through interactions with known hotspot mutations is worthy of research.

DiGeorge Syndrome Associated with Azoospermia: First case in the literature

DiGeorge syndrome (DGS) is one of the most frequently seen chromosomal abnormalities. The major genetic cause of DGS is a microdeletion on chromosome 22q11.2. Majority of the cases are diagnosed during their childhood. DGS is rarely considered and diagnosed in adulthood. Herein, we report the first case of a patient with DGS and azoospermia in the literature. Our patient was a 35-year-old male with mild dysmorphic features, hypernasal voice, mental retardation, and azoospermia. His laboratory tests and echocardiographic assessments were normal. Clinical clues to DGS were hypernasal voice and dysmorphic features with mild mental retardation. The diagnosis of DGS was confirmed by fluorescence in situ hybridization (FISH). Negative effects of cognitive disorders on reproductivity are already known; however, we haven't find any studies in the literature that evaluated infertile patients with DGS using semen analysis, apart from these potential unfavourable effectc of cognitive disorders. Coexistence of DGS and azoospermia may be completely coincidental, but azoospermia can be also one of the unknown clinical features of this syndrome. Many patients with a mild phenotype of DGS may be underdiagnosed. DGS should be considered in adults who have mental, behavioral, or psychiatric disorders with mild dysmorphic features, even in the absence of classical features.

An Adult Case of Chromosome 22q11.2 Deletion Syndrome Associated with a High-positioned Right Aortic Arch

Chromosome 22q11.2 deletion syndrome (22q11.2 DS) has a very wide phenotypic spectrum that includes dysmorphic features, cardiac anomalies, and hypocalcemia arising from hypoparathyroidism. We herein describe an adult case of 22q11.2 DS with associated hypoparathyroidism and anomalies of the aortic arch. Because the patient had been diagnosed with primary hypoparathyroidism at another hospital, a diagnosis of 22q11.2 DS had been overlooked. A chest X-ray examination revealed widening of the mediastinum caused by a high-positioned right aortic arch, and we subsequently confirmed a diagnosis of 22q11.2 DS using fluorescence in situ hybridization. Because primary hypoparathyroidism is a rare disorder, physicians should be aware of the variable phenotypic features of 22q11.2 DS.

Cardiomyocyte-specific conditional knockout of the histone chaperone HIRA in mice results in hypertrophy, sarcolemmal damage and focal replacement fibrosis

HIRA is the histone chaperone responsible for replication-independent incorporation of histone variant H3.3 within gene bodies and regulatory regions of actively transcribed genes, and within the bivalent promoter regions of developmentally regulated genes. The HIRA gene lies within the 22q11.2 deletion syndrome critical region; individuals with this syndrome have multiple congenital heart defects. Because terminally differentiated cardiomyocytes have exited the cell cycle, histone variants should be utilized for the bulk of chromatin remodeling. Thus, HIRA is likely to play an important role in epigenetically defining the cardiac gene expression program. In this study, we determined the consequence of HIRA deficiency in cardiomyocytes in vivo by studying the phenotype of cardiomyocyte-specific Hira conditional-knockout mice. Loss of HIRA did not perturb heart development, but instead resulted in cardiomyocyte hypertrophy and susceptibility to sarcolemmal damage. Cardiomyocyte degeneration gave way to focal replacement fibrosis and impaired cardiac function. Gene expression was widely altered in Hira conditional-knockout hearts. Significantly affected pathways included responses to cellular stress, DNA repair and transcription. Consistent with heart failure, fetal cardiac genes were re-expressed in the Hira conditional knockout. Our results suggest that transcriptional regulation by HIRA is crucial for cardiomyocyte homeostasis.

Thrombocytopenia and Postpartum Hemorrhage in a Woman with Chromosome 22q11.2 Deletion Syndrome

Chromosome 22q11.2 deletion syndrome, also known as DiGeorge or velocardiofacial syndrome, is associated with a wide spectrum of phenotypic features. It is known to be associated with severe macrothrombocytopenia. Postpartum hemorrhage is a leading cause of maternal morbidity and mortality globally. Chromosome 22q11.2 deletion syndrome is rare cause of thrombocytopenia that can be a significant risk factor for life-threatening postpartum hemorrhage. We report a case of postpartum hemorrhage in a woman with 22q11.2 deletion syndrome causing severe macrothrombocytopenia.

Post-childhood Presentation and Diagnosis of DiGeorge Syndrome

BACKGROUND AND OBJECTIVES

The diversity of clinical presentations makes the diagnosis of DiGeorge syndrome (DGS) a diagnostic challenge. The objective of our study was to report the clinical presentation of DGS in the post-childhood period.

METHODS

A retrospective study, investigating patients diagnosed clinically and genetically with DGS at Sheba Medical Center during the period of 2010-2013. Post-childhood period was defined as age >10 years.

RESULTS

During the study period, 29 patients were diagnosed with DGS. Nine (31%) patients with DGS were diagnosed in their post-childhood period. The basis for clinical suspicion was diverse. However, once the suspicion was brought to attention, additional symptoms consistent with DGS were noted at up to 88% of patients who presented characteristic of facial features and developmental delay.

CONCLUSION

Our research shows that diagnosing DGS patients in the post-childhood period is not uncommon. Characteristic facial features and developmental delay, although not leading presenting symptoms, are found very frequently in patients with DGS.

[Efficiency and good tolerance of rituximab for idiopathic thrombocytopenic purpura revealing a 22q11 deletion syndrome]

INTRODUCTION

22q11 deletion is a common genetic disorder which associates a polymalformative syndrome to dysimmune features. Autoimmunity and immune deficiency manifestations are often associated, resulting in a therapeutic challenge for this disease.

CASE REPORT

We report a 28-year-old patient who presented with hemorrhagic manifestations leading to the diagnosis of severe thrombocytopenia (15,000/mm³), of both central and peripheral origin. Patient history, cardio-facial malformative syndrome, hypoparathyroidism and partial immune deficiency led to the molecular diagnosis of 22q11 deletion syndrome. After failure of polyvalent immunoglobulin infusions, rituximab alone allowed the increase of platelets to their usual level of 100-120,000/mm³ within 4 weeks and a complete clinical remission of the hemorrhagic syndrome, without any infectious complication after a 4-year follow-up.

CONCLUSION

Rituximab may be an alternative to corticosteroid for the treatment of auto-immune manifestations associated with minor forms of 22q11 deletion syndrome without significant worsening of the immune deficiency.

A French multicenter study of over 700 patients with 22q11 deletions diagnosed using FISH or aCGH

Although 22q11.2 deletion syndrome (22q11.2DS) is the most recurrent human microdeletion syndrome associated with a highly variable phenotype, little is known about the condition's true incidence and the phenotype at diagnosis. We performed a multicenter, retrospective analysis of postnatally diagnosed patients recruited by members of the Association des Cytogénéticiens de Langue Française (the French-Speaking Cytogeneticists Association). Clinical and cytogenetic data on 749 cases diagnosed between 1995 and 2013 were collected by 31 French cytogenetics laboratories. The most frequent reasons for referral of postnatally diagnosed cases were a congenital heart defect (CHD, 48.6%), facial dysmorphism (49.7%) and developmental delay (40.7%). Since 2007 (the year in which array comparative genomic hybridization (aCGH) was introduced for the routine screening of patients with intellectual disability), almost all cases have been diagnosed using FISH (96.1%). Only 15 cases (all with an atypical phenotype) were diagnosed with aCGH; the deletion size ranged from 745 to 2904 kb. The deletion was inherited in 15.0% of cases and was of maternal origin in 85.5% of the latter. This is the largest yet documented cohort of patients with 22q11.2DS (the most commonly diagnosed microdeletion) from the same population. French cytogenetics laboratories diagnosed at least 108 affected patients (including fetuses) per year from among a national population of ∼66 million. As observed for prenatal diagnoses, CHDs were the most frequently detected malformation in postnatal diagnoses. The most common CHD in postnatal diagnoses was an isolated septal defect.

Regulating Craniofacial Development at the 3' End: MicroRNAs and Their Function in Facial Morphogenesis

Defects in craniofacial development represent a majority of observed human birth defects, occurring at a rate as high as 1:800 live births. These defects often occur due to changes in neural crest cell (NCC) patterning and development and can affect non-NCC-derived structures due to interactions between NCCs and the surrounding cell types. Proper craniofacial development requires an intricate array of gene expression networks that are tightly controlled spatiotemporally by a number of regulatory mechanisms. One of these mechanisms involves the action of microRNAs (miRNAs), a class of noncoding RNAs that repress gene expression by binding to miRNA recognition sequences typically located in the 3' UTR of target mRNAs. Recent evidence illustrates that miRNAs are crucial for vertebrate facial morphogenesis, with changes in miRNA expression leading to facial birth defects, including some in complex human syndromes such as 22q11 (DiGeorge Syndrome). In this review, we highlight the current understanding of miRNA biogenesis, the roles of miRNAs in overall craniofacial development, the impact that loss of miRNAs has on normal development and the requirement for miRNAs in the development of specific craniofacial structures, including teeth. From these studies, it is clear that miRNAs are essential for normal facial development and morphogenesis, and a potential key in establishing new paradigms for repair and regeneration of facial defects.

The First Case Report in Italy of Di George Syndrome Detected by Noninvasive Prenatal Testing

Panorama Plus (Natera), a single-nucleotide polymorphism- (SNP-) based approach that relies on the identification of maternal and fetal allele distributions, allows the detection of common aneuploidies and also incorporates a panel of 5 microdeletions including Di George syndrome. We report here the first case of Di George syndrome detected by NIPT in Italy; blood was drawn at 12 weeks' gestation. The patient had an amniocentesis to confirm the diagnosis by MLPA (multiplex ligation-dependent probe amplification) and an ultrasound aimed to detect the features associated with the syndrome. A right aortic arch and suspect of thymus atrophy were detected, but not other severe malformations typical of the disease. The patient terminated the pregnancy at 17 weeks. NIPT allowed an early screening of Di George syndrome. As the patient was at low risk, it is likely that an ultrasound would have missed the condition.

[22q11.2DS Syndrome as a Genetic Subtype of Schizophrenia]

INTRODUCTION

The 22q11.2 deletion syndrome (22q11.2DS) is associated with the microdeletion of this chromosomal region, and represents the second most common genetic syndrome after Down's syndrome. In patients with schizophrenia, 22q11.2DS has a prevalence of 2%, and in selected groups can be increased to between 32-53%.

OBJECTIVE

To describe the generalities of 22q11.2DS syndrome as a genetic subtype of schizophrenia, its clinical characteristics, molecular genetic aspects, and frequency in different populations.

METHODS

A review was performed from 1967 to 2013 in scientific databases, compiling articles about 22q11.2DS syndrome and its association with schizophrenia.

RESULTS

The 22q11.2 DS syndrome has a variable phenotype associated with other genetic syndromes, birth defects in many tissues and organs, and a high rate of psychiatric disorders, particularly schizophrenia. Likewise, it has been identified in clinical populations with schizophrenia selected by the presence of common syndromic characteristics. FISH, qPCR and MLPA techniques, and recently, aCGH and NGS technologies, are being used to diagnose this microdeletion.

CONCLUSIONS

It is important in clinical practice to remember that people suffering the 22q11.2DS have a high genetic risk for developing schizophrenia, and it is considered that the simultaneous presence of this disease and 22q11.2DS represents a genetic subtype of schizophrenia. There are clear phenotypic criteria, molecular and cytogenetic methods to diagnose this group of patients, and to optimize a multidisciplinary approach in their monitoring.

Self-reported speech problems in adolescents and young adults with 22q11.2 deletion syndrome: a cross-sectional cohort study

Background

Speech problems are a common clinical feature of the 22q11.2 deletion syndrome. The objectives of this study were to inventory the speech history and current self-reported speech rating of adolescents and young adults, and examine the possible variables influencing the current speech ratings, including cleft palate, surgery, speech and language therapy, intelligence quotient, and age at assessment.

Methods

In this cross-sectional cohort study, 50 adolescents and young adults with the 22q11.2 deletion syndrome (ages, 12-26 years, 67% female) filled out questionnaires. A neuropsychologist administered an age-appropriate intelligence quotient test. The demographics, histories, and intelligence of patients with normal speech (speech rating=1) were compared to those of patients with different speech (speech rating>1).

Results

Of the 50 patients, a minority (26%) had a cleft palate, nearly half (46%) underwent a pharyngoplasty, and all (100%) had speech and language therapy. Poorer speech ratings were correlated with more years of speech and language therapy (Spearman's correlation= 0.418, P=0.004; 95% confidence interval, 0.145-0.632). Only 34% had normal speech ratings. The groups with normal and different speech were not significantly different with respect to the demographic variables; a history of cleft palate, surgery, or speech and language therapy; and the intelligence quotient.

Conclusions

All adolescents and young adults with the 22q11.2 deletion syndrome had undergone speech and language therapy, and nearly half of them underwent pharyngoplasty. Only 34% attained normal speech ratings. Those with poorer speech ratings had speech and language therapy for more years.

Interaction of neurodevelopmental pathways and synaptic plasticity in mental retardation, autism spectrum disorder and schizophrenia: implications for psychiatry

OBJECTIVES

Schizophrenia (SCZ), autism spectrum disorder (ASD) and mental retardation (MR) are psychiatric disorders with high heritability. They differ in their clinical presentation and in their time course of major symptoms, which predominantly occurs for MR and ASD during childhood and for SCZ during young adult age. Recent findings with focus on the developmental neurobiology of these disorders emphasize shared mechanisms of common origin. These findings propose a continuum of genetic risk factors impacting on synaptic plasticity with MR causing impairments in global cognitive abilities, ASD in social cognition and SCZ in both global and social cognition.

METHODS

We assess here the historical developments that led to the current disease concepts of the three disorders. We then analyse, based on the functions of genes mutated in two or three of the disorders, selected mechanisms shared in neurodevelopmental pathways and synaptic plasticity.

RESULTS

The analysis of the psychopathological constructs supports the existence of three distinct clinical entities but also elaborates important associations. Similarly, there are common mechanisms especially in global and social cognition.

CONCLUSIONS

We discuss implications from this integrated view on MR, ASD and SCZ for child & adolescent and adult psychiatry in pathophysiology and research perspectives.

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.

A French collaborative survey of 272 fetuses with 22q11.2 deletion: ultrasound findings, fetal autopsies and pregnancy outcomes

OBJECTIVE

The 22q11.2 deletion (del22q11.2) is one of the most common microdeletions. We performed a collaborative, retrospective analysis in France of prenatal diagnoses and outcomes of fetuses carrying the del22q11.2.

METHODS

A total of 272 fetuses were included. Data on prenatal diagnosis, ultrasound findings, pathological features, outcomes and inheritance were analyzed.

RESULTS

The mean time of prenatal diagnosis was 25.6 ± 6 weeks of gestation. Most of the diagnoses (86.8%) were prompted by abnormal ultrasound findings [heart defects (HDs), in 83.8% of cases]. On fetal autopsy, HDs were again the most common disease feature, but thymus, kidney abnormalities and facial dysmorphism were also described. The deletion was inherited in 27% of cases. Termination of pregnancy (TOP) occurred in 68.9% of cases and did not appear to depend on the inheritance status. However, early diagnosis was associated with a higher TOP rate.

CONCLUSION

This is the largest cohort of prenatal del22q11.2 diagnoses. As in postnatally diagnosed cases, HDs were the most frequently observed abnormalities. However, thymus and kidney abnormalities and polyhydramnios should also be screened for in the prenatal diagnosis of del22q11.2. Only the time of diagnosis appeared to be strongly associated with the pregnancy outcome: the earlier the diagnosis, the higher the TOP rate.

Intergenerational and intrafamilial phenotypic variability in 22q11.2 deletion syndrome subjects

BACKGROUND

22q11.2 deletion syndrome (22q11.2DS) is a common microdeletion syndrome, which occurs in approximately 1:4000 births. Familial autosomal dominant recurrence of the syndrome is detected in about 8-28% of the cases. Aim of this study is to evaluate the intergenerational and intrafamilial phenotypic variability in a cohort of familial cases carrying a 22q11.2 deletion.

METHODS

Thirty-two 22q11.2DS subjects among 26 families were enrolled.

RESULTS

Second generation subjects showed a significantly higher number of features than their transmitting parents (212 vs 129, P = 0.0015). Congenital heart defect, calcium-phosphorus metabolism abnormalities, developmental and speech delay were more represented in the second generation (P < 0.05). Ocular disorders were more frequent in the parent group. No significant difference was observed for the other clinical variables. Intrafamilial phenotypic heterogeneity was identified in the pedigrees. In 23/32 families, a higher number of features were found in individuals from the second generation and a more severe phenotype was observed in almost all of them, indicating the worsening of the phenotype over generations. Both genetic and epigenetic mechanisms may be involved in the phenotypic variability.

CONCLUSIONS

Second generation subjects showed a more complex phenotype in comparison to those from the first generation. Both ascertainment bias related to patient selection or to the low rate of reproductive fitness of adults with a more severe phenotype, and several not well defined molecular mechanism, could explain intergenerational and intrafamilial phenotypic variability in this syndrome.

Hippocampal malrotation is associated with chromosome 22q11.2 microdeletion

BACKGROUND

Patients with chromosome 22q11.2 deletion syndrome (22q11DS) are at a seven fold increased risk of developing seizures. However, only a fraction of these patients exhibit structural abnormalities such as polymicrogyria (PMG) and periventricular nodular heterotopia (PNH) that are known to cause seizures and to be associated with 22q11DS. In this study we used a dedicated seizure imaging protocol to look for additional structural abnormalities in these individuals that may explain the elevated risk of seizure disorder in this patient group.

METHODS

Nineteen consecutive adult subjects with 22q11DS underwent a 3 Tesla MRI with a dedicated high-resolution seizure protocol. Neurological exam was performed in all patients. Genome-wide analysis excluded the presence of other pathogenic microdeletions or duplications.

RESULTS

Structural abnormalities were found in 11 of 14 subjects with sufficient image quality. These included three patients with PNH, one of whom had associated PMG. In addition, there was a surprisingly high prevalence of unilateral hippocampal malrotation (HIMAL), observed in 9 of 14 cases (64%). EEG findings showed interictal epileptiform discharges with focal distribution in four patients and generalized discharges in one patient.

CONCLUSION

The results suggest that, in addition to other known structural abnormalities, 22q11DS is associated with HIMAL. It has been suggested that this developmental abnormality of the hippocampus may predispose or otherwise contribute to epileptogenesis. However in this study we observed HIMAL in a large proportion of patients, with and without epilepsy. Therefore, other as yet unknown factors may contribute to the high prevalence of epilepsy in this population.

Prenatal diagnosis of 22q11.2 deletion syndrome in twin pregnancy: a case report

Chromosome 22q11.2 deletion syndrome is a common genetic disorder, also known as DiGeorge syndrome. It occurs in approximately 1:4,000 births, and the incidence is increasing due to affected parents bearing their own affected children. We report the prenatal diagnosis of 22q11.2 deletion syndrome by fluorescence in situ hybridization in twin fetuses having tetralogy of Fallot with absent pulmonary valve.

Expression of autism spectrum and schizophrenia in patients with a 22q11.2 deletion

BACKGROUND

Copy number variants (CNVs) associated with neuropsychiatric disorders are increasingly being identified. While the initial reports were relatively specific, i.e. implicating vulnerability for a particular neuropsychiatric disorder, subsequent studies suggested that most of these CNVs can increase the risk for more than one neuropsychiatric disorder. Possibly, the different neuropsychiatric phenotypes associated with a single genetic variant are really distinct phenomena, indicating pleiotropy. Alternatively, seemingly different disorders could represent the same phenotype observed at different developmental stages or the same underlying pathogenesis with different phenotypic expressions.

AIMS

To examine the relation between autism and schizophrenia in patients sharing the same CNV.

METHOD

We interviewed parents of 78 adult patients with the 22q11.2 deletion (22q11.2DS) to examine if autistic symptoms during childhood were associated with psychosis in adulthood. We used Chi-square, T-tests and logistic regression while entering cognitive level, gender and age as covariates.

RESULTS

The subgroup of 22q11.2DS patients with probable ASD during childhood did not show an increased risk for psychosis in adulthood. The average SRS scores were highly similar between those with and those without schizophrenia.

CONCLUSIONS

ASD and schizophrenia associated with 22q11.2DS should be regarded as two unrelated, distinct phenotypic manifestations, consistent with true neuropsychiatric pleiotropy. 22q11.2DS can serve as a model to examine the mechanisms associated with neuropsychiatric pleiotropy associated with other CNVs.

Palate abnormalities in Chilean patients with chromosome 22q11 microdeletion syndrome

OBJECTIVE

Chromosome 22q11 microdeletion syndrome (del22q11) is the most frequent microdeletion syndrome in humans, with an estimated incidence of 1/4000. It is recognized as a common identifiable cause of cleft palate. We characterized palatal abnormalities in a large cohort of Chilean patients with del22q11.

METHODS

Patients with the deletion were evaluated by geneticists and speech pathologists, including nasopharyngoscopy when indicated. Comparisons between groups with and without palatal abnormalities were performed using Fisher's exact test and Mann-Whitney U test.

RESULTS

Two hundred and one patients were included in the study. Palate abnormalities were present in 154 patients (76.6%). The most frequent finding was submucous cleft palate (both classic and occult forms) seen in 80 patients (39.8% of the total group). Overt cleft palate or cleft lip/palate was seen in 30 patients (14.9%). Patients without palate abnormalities had significantly greater frequency of congenital heart disease and higher mortality.

CONCLUSIONS

Our data show a high frequency of palate abnormalities without significant association with congenital heart disease. The most common types of palate defects seen in this series are usually not evident on physical examination and thus require a high index of suspicion and active evaluation through nasopharyngoscopy.

Clinical applications of schizophrenia genetics: genetic diagnosis, risk, and counseling in the molecular era

Schizophrenia is a complex neuropsychiatric disease with documented clinical and genetic heterogeneity, and evidence for neurodevelopmental origins. Driven by new genetic technologies and advances in molecular medicine, there has recently been concrete progress in understanding some of the specific genetic causes of this serious psychiatric illness. In particular, several large rare structural variants have been convincingly associated with schizophrenia, in targeted studies over two decades with respect to 22q11.2 microdeletions, and more recently in large-scale, genome-wide case-control studies. These advances promise to help many families afflicted with this disease. In this review, we critically appraise recent developments in the field of schizophrenia genetics through the lens of immediate clinical applicability. Much work remains in translating the recent surge of genetic research discoveries into the clinic. The epidemiology and basic genetic parameters (such as penetrance and expression) of most genomic disorders associated with schizophrenia are not yet well characterized. To date, 22q11.2 deletion syndrome is the only established genetic subtype of schizophrenia of proven clinical relevance. We use this well-established association as a model to chart the pathway for translating emerging genetic discoveries into clinical practice. We also propose new directions for research involving general genetic risk prediction and counseling in schizophrenia.

De novo rates and selection of schizophrenia-associated copy number variants

BACKGROUND

At least 10 large and rare recurrent DNA copy number variants (CNVs) have been identified as risk factors for schizophrenia and other neurodevelopmental disorders. Because such conditions are associated with reduced fecundity, these pathogenic CNVs should be filtered out from the population by selection and must be replenished by de novo events.

METHODS

To estimate the mutation rate (μ) for these CNVs and the selection pressure (s) against them, we first conducted a literature review on the rate of each of these CNVs in the population and the rate of their de novo occurrence. In each generation, the number of CNVs lost because of reduced fertility must be replenished by the same number of de novo CNVs. Therefore, the observed ratio of de novo versus all (inherited + de novo) CNVs approximates the selection coefficient (s) of that CNV. The mutation rate approximates to μ = s × q, where q is the frequency of the CNV in the population.

RESULTS

High selection pressure operates at all these loci (s = .12 - .88), suggesting that following de novo occurrence, each of these CNVs persists in the population in only a few generations. The mutation rate for each CNV is high, affecting between 1:3500 and 1:30,000 individuals. The rarest CNVs have the highest selection coefficients.

CONCLUSIONS

The CNVs that increase risk to develop schizophrenia are caused by recent de novo mutations and are under strong selection pressure. They persist in the population because of high mutation rates.

Chromosome 22q11.2 deletion syndrome in African-American patients: a diagnostic challenge

Chromosome 22q11.2 deletion syndrome (22q11DS) is associated with numerous and variable clinical manifestations including conotruncal heart abnormalities, palatal anomalies, hypoparathyroidism, immune deficiency, and cognitive deficits. The clinical suspicion of this syndrome is often heightened by the presence of characteristic facial features. A previous report highlighted the under-diagnosis of this condition in African Americans, thought to be related to a paucity of typical facial features. We ascertained the largest cohort (n = 50) of African-American individuals with 22q11DS reported thus far, across five genetics centers in the United States and report on their facial and other phenotypic features. About 3/4 of our cohort has at least one dysmorphic facial feature. Auricular abnormalities, especially small ears, are the most common dysmorphic facial feature followed by nasal and ocular abnormalities. Skeletal findings are seen in about 2/3 of our cohort, higher than the typical frequency reported in 22q11DS. Cardiac anomalies, developmental delay, and palatal abnormalities are seen at a lower frequency in our cohort. Thus, it is evident that the features traditionally associated with 22q11DS are difficult to recognize in African-American individuals with this syndrome, due to both altered frequencies of major anomalies and a non-classic facial appearance. Therefore, a high index of suspicion is needed to recognize 22q11DS in African-American individuals.

Adults with Rubinstein-Taybi syndrome

Information in the medical literature regarding adults with genetic syndromes is limited, making the care of these patients challenging. We conducted a questionnaire study of adults with Rubinstein-Taybi syndrome that addressed medical problems, education, independence, and behavior. The most common medical problems included short stature, obesity, visual difficulties, keloids, eating problems, spine curvature, and joint problems. The adults had typically moderate mental retardation, but most achieved some independence in self-care and communication; many participated in supported work situations. However, approximately one-third were said to have some decreased abilities over time. Behavior problems were common and often worsened with age. Very few of the study participants were seeing a geneticist as an adult. Long-term involvement of geneticists and education of adult primary care providers may help with many of the challenges facing adults with RTS and their families.

Síndrome de deleção 22q11.2 e cardiopatias congênitas

OBJETIVO: Revisar as características clínicas, etiológicas e diagnósticas da síndrome de deleção 22q11 e sua associação com as cardiopatias congênitas. FONTES DOS DADOS: Foram pesquisados artigos científicos presentes nos portais Medline, Lilacs e SciELO, utilizando-se descritores específicos como "22q11", "DiGeorge syndrome", "velocardiofacial syndrome", "congenital heart defects" e "cardio-vascular malformations". O período adotado para a revisão foi de 1980 a 2009. SÍNTESE DOS DADOS: As malformações cardíacas são os defeitos congênitos observados mais frequentemente ao nascimento e representam um problema importante de Saúde Pública. Dentre suas principais causas conhecidas destaca-se a síndrome de deleção 22q11, também chamada de síndrome de DiGeorge, síndrome velocardiofacial e CATCH22. Trata-se de uma doença autossômica domi-nante caracterizada por um fenótipo altamente variável, o que dificulta em muito seu reconhecimento clínico. Além disso, a maior parte dos pacientes apresenta uma microdeleção identificada principalmente por técnicas de citogenética molecular, como a hibridização in situ fluorescente, pouco disponíveis em nosso meio. De forma similar a outras síndromes, a síndrome de deleção 22q11 associa-se a certos defeitos cardíacos específicos, no caso os do tipo conotruncal. Apesar disso, não há ainda na literatura um consenso sobre quais os pacientes com car-diopatia congênita que deveriam ser investigados para a síndrome de deleção 22q11. CONCLUSÕES: Cardiologistas e cirurgiões cardíacos, espe-cialmente pediátricos, devem estar cientes das peculiaridades e dos cuidados dispensados à síndrome de deleção 22q11. Os indivíduos com a síndrome apresentam comumente alterações envolvendo vários sistemas, o que pode levar a dificuldades e a complicações durante seu manejo clínico e cirúrgico.

Complex congenital heart disease in unaffected relatives of adults with 22q11.2 deletion syndrome

The 22.q11.2 deletion syndrome (22q11DS) is a common genetic condition associated with 22q11.2 microdeletions and classically has included congenital heart disease (CHD) as a part of the variable expression. Some evidence has shown that relatives of those with 22q11DS might be at an increased risk of CHD in the absence of 22q11.2 deletions. We obtained a detailed family history of CHD in the first- to third-degree relatives (n = 2,639) of 104 adult probands with 22q11DS. We compared the prevalence of CHD in the relatives without 22q11.2 deletions to the published general population prevalence. We also investigated the effect of CHD in the probands on prevalence of CHD in the relatives. Of the 104 probands with 22q11DS, 14 (13.5%) had 17 relatives (17 of 2,639, 0.6%) with CHD. Of 66 probands with CHD, 15 (0.9%) of their 1,663 relatives had CHD, a significantly greater prevalence than that for the relatives of probands without CHD (0.2%, 2 of 976, p = 0.041, odds ratio 4.43, 95% confidence interval 1.03 to 40.00). In relatives of probands with CHD, the prevalence of those with severe CHD (0.36%) was significantly elevated compared to population expectations (0.061%, p = 0.007, odds ratio 5.88, 95% confidence interval 2.16 to 12.85). In conclusion, these results support a heritable susceptibility to CHD in families of probands with 22q11DS, in addition to that imparted by microdeletion 22q11.2. The occurrence of CHD in relatives might be related to the expression of CHD in the proband with 22q11DS. These findings have potential implications for the genetic counseling of families of those with 22q11DS and support the notion that interacting genetic variants might contribute to the variable expression of 22q11DS.