Practical guidelines for managing adults with 22q11.2 deletion syndrome

Pediatric healthcare costs for patients with 22q11.2 deletion syndrome

BACKGROUND

The 22q11.2 deletion syndrome is a variably expressed disorder that can include cardiac, palate, and other physical abnormalities, immunodeficiency, and hypocalcemia. Because of the extreme variability in phenotype, there has been no available estimate of the total medical expenditure associated with the average case.

METHODS

We have developed a model to estimate the cost from the time of diagnosis to age 20. Costs were based on patients seen at a specialty center but also considered those components of care expected to have been provided by external healthcare facilities. Expense was based on billed medical charges extracted from the electronic medical billing system for all patients with a diagnosis of DiGeorge or velocardiofacial syndrome from 1993-2015. Expenditures included maternal prenatal care directly related to an affected pregnancy, molecular/cytogenetic diagnosis, consultations, surgery, and/or other treatment and management. Most mental health services (except inpatient), therapy related to cognitive, behavioral, speech, pharmacy, and nonmedical costs (special education, vocational, respite, lost earnings) were not included.

RESULTS

Data were available for 642 patients with 50.7% diagnosed prenatally or in the first year of life. The average cost for a patient was $727,178. Costs were highest for patients ascertained prenatally ($2,599,955) or in the first year of life ($1,043,096), those with cardiac abnormalities or referred for cardiac evaluation ($751,535), and patients with low T-cell counts ($1,382,222).

CONCLUSION

This study demonstrates that there are significant medical costs associated with 22q11.2 deletion syndrome.

Neuroradiographic findings in 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2DS) is a common genetic disorder with enormous phenotypic heterogeneity. Despite the established prevalence of developmental and neuropsychiatric issues in this syndrome, its neuroanatomical correlates are not as well understood. A retrospective chart review was performed on 111 patients diagnosed with 22q11.2DS. Of the 111 patients, 24 with genetically confirmed 22q11.2 deletion and brain MRI or MRA were included in this study. The most common indications for imaging were unexplained developmental delay (6/24), seizures of unknown etiology (5/24), and unilateral weakness (3/24). More than half (13/24) of the patients had significant radiographic findings, including persistent cavum septi pellucidi and/or cavum vergae (8/24), aberrant cortical veins (6/24), polymicrogyria or cortical dysplasia (4/24), inner ear deformities (3/24), hypoplastic internal carotid artery (2/24), and hypoplastic cerebellum (1/24). These findings reveal the types and frequencies of brain malformations in this case series, and suggest that the prevalence of neuroanatomical abnormalities in 22q11.2DS may be underestimated. Understanding indications for imaging and frequently encountered brain malformations will result in early diagnosis and intervention in an effort to optimize patient outcomes.

Delayed diagnosis of 22q11 deletion syndrome due to late onset hypocalcemia in a 11-year-old girl with imperforated anus

Neonatal hypocalcemia and congenital heart defects has been known as the first clinical manifestation of the chromosome 22q11.2 deletion syndrome (22q11DS). However, because of its wide clinical spectrum, diagnosis of 22q11DS can be delayed in children without classic symptoms. We report the case of a girl with the history of imperforate anus but without neonatal hypocalcemia or major cardiac anomaly, who was diagnosed for 22q11DS at the age of 11 after the onset of overt hypocalcemia. She was born uneventfully from phenotypically normal Korean parents. Imperforate anus and partial cleft palate were found at birth, which were surgically repaired thereafter. There was no history of neonatal hypocalcemia, and karyotyping by GTG banding was normal. At the age of 11, hypocalcemia (serum calcium, 5.0 mg/dL) and decreased parathyroid hormone level (10.8 pg/mL) was noted when she visited our Emergency Department for fever and vomiting. The 22q11DS was suspected because of her mild mental retardation and velopharyngeal insufficiency, and a microdeletion on chromosome 22q11.2 was confirmed by fluorescence in situ hybridization. The 22q11DS should be considered in the differential diagnosis of hypocalcemia at any age because of its wide clinical spectrum.

Association of airway abnormalities with 22q11.2 deletion syndrome

INTRODUCTION

22q11.2 deletion syndrome (22q11.2DS) presents with complex but variable symptoms, including cardiac, immune, palatal, endocrine, cognitive, and psychiatric issues. However, an association of 22q11.2DS with structural airway abnormalities has not been formally described. The aim of this study was to document the frequency of this association.

METHODS

We retrospectively reviewed medical records of patients with 22q11.2DS evaluated in the 22q and You Center at the Children's Hospital of Philadelphia between 1999 and 2015 referred to otolaryngology for an airway assessment. Type of airway abnormality and presence of comorbidities, such as congenital heart disease, tracheostomy, and association with prenatal symptomatology such as polyhydramnios, were noted.

RESULTS

Of the 104 patients who underwent an otolaryngology procedure (microlaryngoscopy or bronchoscopy), 71% (n = 74) had airway abnormalities. Patients with airway abnormalities ranged in age from 5 months to 37 years, with similar prevalence among males and females. Observed airway abnormalities included tracheomalacia (36%), subglottic stenosis (28%), laryngomalacia (26%), glottic web (21%), and bronchomalacia (16%). Most patients with airway abnormalities (91%) had an associated congenital heart defect, with ventricular septal defect and Tetralogy of Fallot being the most prevalent. Importantly, 30% of patients required a tracheostomy, and overall polyhydramnios was noted in 16% of pregnancies.

CONCLUSION

Airway abnormalities are a common feature of 22q11.2DS, leading to substantial morbidity, particularly when combined with complex cardiac disease. Polyhydramnios may be an important prenatal clue to both the diagnosis of 22q11.2DS and airway anomalies. Postnatal assessment of airway structure and function among patients with 22q11.2DS is an important component of overall evaluation and will help guide long-term management.

Update on the 22q11.2 deletion syndrome and its relevance to schizophrenia

PURPOSE OF REVIEW

Schizophrenia occurs in ∼25% of individuals with 22q11.2 deletion syndrome (22q11.2DS), the strongest known molecular genetic risk factor for schizophrenia. This review highlights recent literature in 22q11.2DS as it pertains to psychosis and schizophrenia.

RECENT FINDINGS

Advances in noninvasive prenatal testing allow for early detection of 22q11.2DS in utero, whereas premature birth has been shown to be a significant risk factor for development of psychotic illness in 22q11.2DS. Impairments in various domains of cognitive and social functioning, as well as neuroanatomical alterations, are comparable with those in other high-risk groups and may serve as early signs of psychosis in 22q11.2DS. Novel research on the pathogenesis of schizophrenia in 22q11.2DS using cellular and mouse models indicates changes in expression of genes within the 22q11.2 deletion region and elsewhere in the genome, implicating molecular pathways involved in schizophrenia and associated neurocognitive deficits. Increased risks of obesity and of Parkinson's disease in 22q11.2DS warrant consideration in antipsychotic management.

SUMMARY

Progress in characterizing and predicting psychotic illness in 22q11.2DS supports this identifiable subpopulation as a molecular model with important implications for understanding the pathogenesis of schizophrenia in the general population and for development of potential novel therapies.

Whole-genome sequencing suggests mechanisms for 22q11.2 deletion-associated Parkinson's disease

OBJECTIVES

To investigate disease risk mechanisms of early-onset Parkinson's disease (PD) associated with the recurrent 22q11.2 deletion, a genetic risk factor for early-onset PD.

METHODS

In a proof-of-principle study, we used whole-genome sequencing (WGS) to investigate sequence variants in nine adults with 22q11.2DS, three with neuropathologically confirmed early-onset PD and six without PD. Adopting an approach used recently to study schizophrenia in 22q11.2DS, here we tested candidate gene-sets relevant to PD.

RESULTS

No mutations common to the cases with PD were found in the intact 22q11.2 region. While all were negative for rare mutations in a gene-set comprising PD disease-causing and risk genes, another candidate gene-set of 1000 genes functionally relevant to PD presented a nominally significant (P = 0.03) enrichment of rare putatively damaging missense variants in the PD cases. Polygenic score results, based on common variants associated with PD risk, were non-significantly greater in those with PD.

CONCLUSIONS

The results of this first-ever pilot study of WGS in PD suggest that the cumulative burden of genome-wide sequence variants may contribute to expression of early-onset PD in the presence of threshold-lowering dosage effects of a 22q11.2 deletion. We found no evidence that expression of PD in 22q11.2DS is mediated by a recessive locus on the intact 22q11.2 chromosome or mutations in known PD genes. These findings offer initial evidence of the potential effects of multiple within-individual rare variants on the expression of PD and the utility of next generation sequencing for studying the etiology of PD.

22q11.2 deletion syndrome in diverse populations

22q11.2 deletion syndrome (22q11.2 DS) is the most common microdeletion syndrome and is underdiagnosed in diverse populations. This syndrome has a variable phenotype and affects multiple systems, making early recognition imperative. In this study, individuals from diverse populations with 22q11.2 DS were evaluated clinically and by facial analysis technology. Clinical information from 106 individuals and images from 101 were collected from individuals with 22q11.2 DS from 11 countries; average age was 11.7 and 47% were male. Individuals were grouped into categories of African descent (African), Asian, and Latin American. We found that the phenotype of 22q11.2 DS varied across population groups. Only two findings, congenital heart disease and learning problems, were found in greater than 50% of participants. When comparing the clinical features of 22q11.2 DS in each population, the proportion of individuals within each clinical category was statistically different except for learning problems and ear anomalies (P < 0.05). However, when Africans were removed from analysis, six additional clinical features were found to be independent of ethnicity (P ≥ 0.05). Using facial analysis technology, we compared 156 Caucasians, Africans, Asians, and Latin American individuals with 22q11.2 DS with 156 age and gender matched controls and found that sensitivity and specificity were greater than 96% for all populations. In summary, we present the varied findings from global populations with 22q11.2 DS and demonstrate how facial analysis technology can assist clinicians in making accurate 22q11.2 DS diagnoses. This work will assist in earlier detection and in increasing recognition of 22q11.2 DS throughout the world.

Incidence of the 22q11.2 deletion in a large cohort of miscarriage samples

Background

The 22q11.2 deletion syndrome is the most common microdeletion syndrome in livebirths, but data regarding its incidence in other populations is limited and also include ascertainment bias. This study was designed to determine the incidence of the 22q11.2 deletion in miscarriage samples sent for clinical molecular cytogenetic testing.

Results

Twenty-six thousand one hundred one fresh product of conception (POC) samples were sent to a CLIA- certified, CAP-accredited laboratory from April 2010–-May 2016 for molecular cytogenetic miscarriage testing using a single-nucleotide polymorphism (SNP)-based microarray platform. A retrospective review determined the incidence of the 22q11.2 deletion in this sample set. Fetal results were obtained in 22,451 (86%) cases, of which, 15 (0.07%) had a microdeletion in the 22q11.2 region (incidence, 1/1497). Of those, 12 (80%) cases were found in samples that were normal at the resolution of traditional karyotyping (i.e., had no chromosome abnormalities above 10 Mb in size) and three (20%) cases had additional findings (Trisomy 15, Trisomy 16, XXY). Ten (67%) cases with a 22q11.2 deletion had the common ~3 Mb deletion; the remaining 5 cases had deletions ranging in size from 0.65 to 1.5 Mb. A majority (12/15) of cases had a deletion on the maternally inherited chromosome. No significant relationship between maternal age and presence of a fetal 22q11.2 deletion was observed.

Conclusions

The observed incidence of 1/1497 for the 22q11.2 deletion in miscarriage samples is higher than the reported general population prevalence (1/4000–1/6000). Further research is needed to determine whether the 22q11.2 deletion is a causal factor for miscarriage.

Hypothyroidism associated with parathyroid disorders

Hypothyroidism may occur in association with congenital parathyroid disorders determining parathyroid hormone insufficiency, which is characterized by hypocalcemia and concomitant inappropriately low secretion of parathormone (PTH). The association is often due to loss of function of genes common to thyroid and parathyroid glands embryonic development. Hypothyroidism associated with hypoparathyroidism is generally mild and not associated with goiter; moreover, it is usually part of a multisystemic involvement not restricted to endocrine function as occurs in patients with 22q11 microdeletion/DiGeorge syndrome, the most frequent disorders. Hypothyroidism and hypoparathyroidism may also follow endocrine glands' damages due to autoimmunity or chronic iron overload in thalassemic disorders, both genetically determined conditions. Finally, besides PTH deficiency, hypocalcemia can be due to PTH resistance in pseudohypoparathyroidism; when hormone resistance is generalized, patients can suffer from hypothyroidism due to TSH resistance. In evaluating patients with hypothyroidism and hypocalcemia, physical examination and clinical history are essential to drive the diagnostic process, while routine genetic screening is not recommended.

Obesity in adults with 22q11.2 deletion syndrome

PURPOSE

To characterize the prevalence of and contributing factors to adult obesity in the most common recurrent copy-number variation (CNV), 22q11.2 deletion, given that other rare CNVs are known to have obesity phenotypes.

METHODS

In 207 adults with 22q11.2 deletion syndrome (22q11.2DS), we used available height and weight measurements to calculate body mass index (BMI) and recorded associated factors that could play a role in obesity. We used the maximum BMI per subject and logistic regression to test a model predicting obesity class.

RESULTS

The prevalence of obesity (BMI ≥30) in 22q11.2DS (n = 90, 43.5%; at median age of 26.7 years) was significantly greater than for Canadian norms (odds ratio (OR) 2.30, 95% confidence interval (CI) = 1.74-3.02, P < 0.0001), even after excluding individuals with a history of antipsychotic use. The regression model was significant (P < 0.0001). Psychotropic medication use and age, but not sex or presence of intellectual disability, were associated with higher obesity level. Ten (4.8%) individuals were diagnosed with type 2 diabetes at a median age of 39.5 years; the prevalence was higher in those with obesity (P < 0.01).

CONCLUSION

The results suggest that adult obesity is related to the 22q11.2 deletion. The findings expand the potential genetic causes of obesity and have important implications for management of 22q11.2DS.Genet Med 19 2, 204-208.

Amniotic Band Syndrome, Perinatal Hospice, and Palliative Care versus Active Management

Introduction. Amniotic band syndrome and sequence are a relatively rare condition in which congenital anomalies occur as a result of the adherence and entrapment of fetal parts with coarse fibrous bands of the amniotic membrane. A large percentage of reported cases have an atypical gestational history. The frequency of this obstetric complication is not affected by fetal gender, genetic abnormality, or prenatal infection. Case. A 21-year-old, G1P0 female parturient at 18 weeks and 5 days with a single intrauterine gestation during a routine ultrasound evaluation was noted to have amniotic band sequence. The pregnancy was subsequently complicated by preterm premature rupture of membranes with oligohydramnios, resulting in a surviving neonate scheduled for rehabilitative treatment. Conclusion. Amniotic band syndrome is an uncommon congenital anomaly resulting in multiple disfiguring and disabling manifestations. Several theories are proposed with most involving early rupture of the amnion and entanglement of fetal parts by amniotic bands. This syndrome can be manifested by development of multiple malformations, with the majority of the defects being limb abnormalities of a disorganized nature, as in the case we present. In the absence of a clear etiology of consequential congenital abnormalities, obstetric management guidelines should use shared decision models to focus on the quality of life for the offspring.

Neuropsychiatric aspects of 22q11.2 deletion syndrome: considerations in the prenatal setting

Most major neuropsychiatric outcomes of concern to families are not detectable by prenatal ultrasound. The introduction of genome-wide chromosomal microarray analysis to prenatal clinical diagnostic testing has increased the detection of pathogenic 22q11.2 deletions, which cause the most common genomic disorder. The recent addition of this and other microdeletions to non-invasive prenatal screening methods using cell-free fetal DNA has further propelled interest in outcomes. Conditions associated with 22q11.2 deletions include intellect ranging from intellectual disability to average, schizophrenia and other treatable psychiatric conditions, epilepsy, and early-onset Parkinson's disease. However, there is currently no way to predict how severe the lifetime expression will be. Available evidence suggests no major role in these neuropsychiatric outcomes for the congenital cardiac or most other structural anomalies that may be detectable on ultrasound. This article provides an outline of the lifetime neuropsychiatric phenotype of 22q11.2 deletion syndrome that will be useful to clinicians involved in prenatal diagnosis and related genetic counselling. The focus is on information that will be most relevant to two common situations: detection of a 22q11.2 deletion in a fetus or newborn, and new diagnosis of 22q11.2 deletion syndrome in a parent without a previous molecular diagnosis. © 2016 John Wiley & Sons, Ltd.

[Diagnosis of 22q11.2 deletion syndrome in the context of newly developed psychosis]

22q11.2 deletion syndrome (clinically also known as velocardiofacial or DiGeorge syndrome) is the most common human microdeletion syndrome and can be associated with a multitude of clinical features. In this article we report the case of a 22-year-old patient from Austria who was diagnosed with previously unknown 22q11.2 deletion syndrome in the context of newly developed psychosis. Using this case as an example, we then discuss the implications of 22q11.2 deletion syndrome for clinical psychiatric practice.

Camptodactyly and the 22q11.2 deletion syndrome

We describe a 5-day-old male with minor facial anomalies, a congenital laryngeal web, severe laryngomalacia, and prominent fixed flexion of the proximal interphalangeal joints of digits 2 through 5 bilaterally. A whole genome SNP microarray analysis identified a 2.55 Mb interstitial deletion of 22q11.21, typical of that seen in the DiGeorge and Velocardiofacial syndromes. A review of the literature identifies 10 other cases with camptodactyly. Camptodactyly appears to be an associated but rarely reported anomaly in patients with the 22q11.2 microdeletion syndrome. © 2016 Wiley Periodicals, Inc.

The importance of copy number variation in congenital heart disease

Congenital heart disease (CHD) is the most common class of major malformations in humans. The historical association with large chromosomal abnormalities foreshadowed the role of submicroscopic rare copy number variations (CNVs) as important genetic causes of CHD. Recent studies have provided robust evidence for these structural variants as genome-wide contributors to all forms of CHD, including CHD that appears isolated without extra-cardiac features. Overall, a CNV-related molecular diagnosis can be made in up to one in eight patients with CHD. These include de novo and inherited variants at established (chromosome 22q11.2), emerging (chromosome 1q21.1), and novel loci across the genome. Variable expression of rare CNVs provides support for the notion of a genetic spectrum of CHD that crosses traditional anatomic classification boundaries. Clinical genetic testing using genome-wide technologies (e.g., chromosomal microarray analysis) is increasingly employed in prenatal, paediatric and adult settings. CNV discoveries in CHD have translated to changes to clinical management, prognostication and genetic counselling. The convergence of findings at individual gene and at pathway levels is shedding light on the mechanisms that govern human cardiac morphogenesis. These clinical and research advances are helping to inform whole-genome sequencing, the next logical step in delineating the genetic architecture of CHD.

Cardiac sympathetic activity in 22q11.2 deletion syndrome

AIM

22q11.2 deletion syndrome (22q11.2DS) affects catechol-O-methyl-transferase (COMT), which involves the degradation of norepinephrine (NE). Clinically, adults with 22q11.2DS are at increased risk for sudden unexpected death. Although the causes are likely multifactorial, increased cardiac sympathetic activity with subsequent fatal arrhythmia, due to increased levels of NE, should be considered as a possible mechanism predisposing to this premature death. The purpose of this study was to determine whether cardiac sympathetic activity is increased in 22q11.2DS, both at baseline and following an acute NE depletion with alpha-methyl-para-tyrosine (AMPT).

METHODS

Five adults with 22q11.2DS and five age- and sex-matched healthy controls underwent 2 sessions with either AMPT or placebo administration before (123)I-mIBG scintigraphy. Heart-to-mediastinum ratios (H/M) were determined from the images 15min (early) and 4h (late) after administration of (123)I-mIBG and the washout (WO) was calculated as an indicator of adrenergic drive.

RESULTS

At baseline there were no significant differences in both early and late H/M between 22q11.2DS and controls. However, there was a significant difference in WO between 22q11.2DS and controls (-4.92±2.8 and -10.44±7.2, respectively; p=0.027), but a "negative WO" does not support an increased sympathetic drive. In addition there was a trend towards a higher late H/M after AMPT administration compared to baseline which was more pronounced in 22q11.2DS.

CONCLUSION

This study for the first time suggests normal cardiac sympathetic activity in adults with 22q11.2DS assessed by (123)I-mIBG scintigraphy. Although there is a small difference in adrenergic drive compared to healthy subjects, this most likely does not explain the increased unexpected death rate in the 22q11.2 DS population.

Two patients with chromosome 22q11.2 deletion presenting with childhood obesity and hyperphagia

Chromosome 22q11.2 deletion syndrome is a clinically heterogeneous condition of intellectual disability, parathyroid and thyroid hypoplasia, palatal abnormalities, cardiac malformations and psychiatric symptoms. Hyperphagia and childhood obesity is widely reported in Prader-Willi Syndrome (PWS) but there is only one previous report of this presentation in chromosome 22q11.2 deletion syndrome. We describe two further cases of chromosome 22q11.2 deletion syndrome in which hyperphagia and childhood obesity were the presenting features. This may be a manifestation of obsessive behaviour secondary to some of the psychiatric features commonly seen in chromosome 22q11.2 deletion syndrome. Serious complications may result from hyperphagia and childhood obesity therefore early recognition and intervention is crucial. Due to the similar clinical presentation of these two patients to patients with PWS, it is suggested that the hyperphagia seen here should be managed in a similar way to how it is managed in PWS.

Deletions at 22q11.2 in idiopathic Parkinson's disease: a combined analysis of genome-wide association data

BACKGROUND

Parkinson's disease has been reported in a small number of patients with chromosome 22q11.2 deletion syndrome. In this study, we screened a series of large, independent Parkinson's disease case-control studies for deletions at 22q11.2.

METHODS

We used data on deletions spanning the 22q11.2 locus from four independent case-control Parkinson's disease studies (UK Wellcome Trust Case Control Consortium 2, Dutch Parkinson's Disease Genetics Consortium, US National Institute on Aging, and International Parkinson's Disease Genomics Consortium studies), which were independent of the original reports of chromosome 22q11.2 deletion syndrome. We did case-control association analysis to compare the proportion of 22q11.2 deletions found, using the Fisher's exact test for the independent case-control studies and the Mantel-Haenszel test for the meta-analyses. We retrieved clinical details of patients with Parkinson's disease who had 22q11.2 deletions from the medical records of these patients.

FINDINGS

We included array-based copy number variation data from 9387 patients with Parkinson's disease and 13 863 controls. Eight patients with Parkinson's disease and none of the controls had 22q11.2 deletions (p=0·00082). In the 8451 patients for whom age at onset data were available, deletions at 22q11.2 were associated with Parkinson's disease age at onset (Mann-Whitney U test p=0·001). Age at onset of Parkinson's disease was lower in patients carrying a 22q11.2 deletion (median 37 years, 95% CI 32·0-55·5; mean 42·1 years [SD 11·9]) than in those who did not carry a deletion (median 61 years, 95% CI 60·5-61·0; mean 60·3 years [SD 12·8]). A 22q11.2 deletion was present in more patients with early-onset (p<0·0001) and late-onset Parkinson's disease (p=0·016) than in controls, and in more patients with early-onset than late-onset Parkinson's disease (p=0·005).

INTERPRETATION

Clinicians should be alert to the possibility of 22q11.2 deletions in patients with Parkinson's disease who have early presentation or features associated with the chromosome 22q11.2 deletion syndrome, or both.

FUNDING

UK Medical Research Council, UK Wellcome Trust, Parkinson's UK, Patrick Berthoud Trust, National Institutes of Health, "Investissements d'Avenir" ANR-10-IAIHU-06, Dutch Parkinson Foundation (Parkinson Vereniging), Neuroscience Campus Amsterdam, National Institute for Health Research, National Institute on Aging, National Institutes of Health.

The importance of understanding cognitive trajectories: the case of 22q11.2 deletion syndrome

PURPOSE OF REVIEW

The 22q11.2 deletion syndrome (velo-cardio-facial syndrome or DiGeorge syndrome) is the most common known contiguous gene deletion syndrome, and is associated with neurodevelopmental problems and diverse neuropsychiatric disorders across the life span. In this review, we discuss the wide variability in intelligence, the developmental phenotypic transitions regarding cognitive development (intelligence) from preschool to adolescence, and the importance of understanding these cognitive trajectories in 22q11.2 deletion syndrome for care/management and research.

RECENT FINDINGS

Longitudinal data on the cognitive development of children and adolescents with 22q11.2 deletion syndrome reveal divergent cognitive trajectories. A decline in verbal intelligence quotient precedes the onset of psychosis in 22q11.2 deletion syndrome.

SUMMARY

Understanding these cognitive trajectories is important since it can guide clinicians to develop adequate support, tailored remediation, and psychiatric care and individualized follow-up.

22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2DS) is the most common chromosomal microdeletion disorder, estimated to result mainly from de novo non-homologous meiotic recombination events occurring in approximately 1 in every 1,000 fetuses. The first description in the English language of the constellation of findings now known to be due to this chromosomal difference was made in the 1960s in children with DiGeorge syndrome, who presented with the clinical triad of immunodeficiency, hypoparathyroidism and congenital heart disease. The syndrome is now known to have a heterogeneous presentation that includes multiple additional congenital anomalies and later-onset conditions, such as palatal, gastrointestinal and renal abnormalities, autoimmune disease, variable cognitive delays, behavioural phenotypes and psychiatric illness - all far extending the original description of DiGeorge syndrome. Management requires a multidisciplinary approach involving paediatrics, general medicine, surgery, psychiatry, psychology, interventional therapies (physical, occupational, speech, language and behavioural) and genetic counselling. Although common, lack of recognition of the condition and/or lack of familiarity with genetic testing methods, together with the wide variability of clinical presentation, delays diagnosis. Early diagnosis, preferably prenatally or neonatally, could improve outcomes, thus stressing the importance of universal screening. Equally important, 22q11.2DS has become a model for understanding rare and frequent congenital anomalies, medical conditions, psychiatric and developmental disorders, and may provide a platform to better understand these disorders while affording opportunities for translational strategies across the lifespan for both patients with 22q11.2DS and those with these associated features in the general population.

Whole-Genome Sequencing Suggests Schizophrenia Risk Mechanisms in Humans with 22q11.2 Deletion Syndrome

Chromosome 22q11.2 microdeletions impart a high but incomplete risk for schizophrenia. Possible mechanisms include genome-wide effects of DGCR8 haploinsufficiency. In a proof-of-principle study to assess the power of this model, we used high-quality, whole-genome sequencing of nine individuals with 22q11.2 deletions and extreme phenotypes (schizophrenia, or no psychotic disorder at age >50 years). The schizophrenia group had a greater burden of rare, damaging variants impacting protein-coding neurofunctional genes, including genes involved in neuron projection (nominal P = 0.02, joint burden of three variant types). Variants in the intact 22q11.2 region were not major contributors. Restricting to genes affected by a DGCR8 mechanism tended to amplify between-group differences. Damaging variants in highly conserved long intergenic noncoding RNA genes also were enriched in the schizophrenia group (nominal P = 0.04). The findings support the 22q11.2 deletion model as a threshold-lowering first hit for schizophrenia risk. If applied to a larger and thus better-powered cohort, this appears to be a promising approach to identify genome-wide rare variants in coding and noncoding sequence that perturb gene networks relevant to idiopathic schizophrenia. Similarly designed studies exploiting genetic models may prove useful to help delineate the genetic architecture of other complex phenotypes.

Comparative mapping of the 22q11.2 deletion region and the potential of simple model organisms

Background

22q11.2 deletion syndrome (22q11.2DS) is the most common micro-deletion syndrome. The associated 22q11.2 deletion conveys the strongest known molecular risk for schizophrenia. Neurodevelopmental phenotypes, including intellectual disability, are also prominent though variable in severity. Other developmental features include congenital cardiac and craniofacial anomalies. Whereas existing mouse models have been helpful in determining the role of some genes overlapped by the hemizygous 22q11.2 deletion in phenotypic expression, much remains unknown. Simple model organisms remain largely unexploited in exploring these genotype-phenotype relationships.

Methods

We first developed a comprehensive map of the human 22q11.2 deletion region, delineating gene content, and brain expression. To identify putative orthologs, standard methods were used to interrogate the proteomes of the zebrafish (D. rerio), fruit fly (D. melanogaster), and worm (C. elegans), in addition to the mouse. Spatial locations of conserved homologues were mapped to examine syntenic relationships. We systematically cataloged available knockout and knockdown models of all conserved genes across these organisms, including a comprehensive review of associated phenotypes.

Results

There are 90 genes overlapped by the typical 2.5 Mb deletion 22q11.2 region. Of the 46 protein-coding genes, 41 (89.1 %) have documented expression in the human brain. Identified homologues in the zebrafish (n = 37, 80.4 %) were comparable to those in the mouse (n = 40, 86.9 %) and included some conserved gene cluster structures. There were 22 (47.8 %) putative homologues in the fruit fly and 17 (37.0 %) in the worm involving multiple chromosomes. Individual gene knockdown mutants were available for the simple model organisms, but not for mouse. Although phenotypic data were relatively limited for knockout and knockdown models of the 17 genes conserved across all species, there was some evidence for roles in neurodevelopmental phenotypes, including four of the six mitochondrial genes in the 22q11.2 deletion region.

Conclusions

Simple model organisms represent a powerful but underutilized means of investigating the molecular mechanisms underlying the elevated risk for neurodevelopmental disorders in 22q11.2DS. This comparative multi-species study provides novel resources and support for the potential utility of non-mouse models in expression studies and high-throughput drug screening. The approach has implications for other recurrent copy number variations associated with neurodevelopmental phenotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s11689-015-9113-x) contains supplementary material, which is available to authorized users.

Fetal growth and gestational factors as predictors of schizophrenia in 22q11.2 deletion syndrome

PURPOSE

Schizophrenia occurs in 20-25% of adults with 22q11.2 deletion syndrome (22q11.2DS). General population studies of schizophrenia report associations with perinatal complications, although effect sizes are generally low. We aimed to determine whether such factors are associated with expression of schizophrenia in individuals with 22q11.2DS.

METHODS

We investigated the relationship of small for gestational age (SGA) birth weight (<3rd percentile for sex and gestational age) and prematurity (<37 weeks gestation) to expression of schizophrenia in a well-characterized cohort of 123 adults with 22q11.2DS. Outcome measures included adjusted odds ratios and positive and negative predictive values (PPV and NPV) for schizophrenia.

RESULTS

SGA birth weight (OR = 3.52, 95% CI = 1.34-9.22) and prematurity (OR = 5.38, 95% CI = 1.63-17.75), but not maternal factors, were significant risk factors for schizophrenia in 22q11.2DS. Being born SGA or premature resulted in a PPV of 46% for schizophrenia; NPV in the absence of both features was 83%. Post hoc analyses suggested these perinatal complications were also associated with factors indicative of increased severity of schizophrenia.

CONCLUSION

In 22q11.2DS, fetal growth and gestation may have a clinically significant impact on future risk for schizophrenia. These data advance our understanding of determinants of disease-specific expression in 22q11.2DS, with implications for other genomic disorders.Genet Med 18 4, 350-355.

Response to clozapine in a clinically identifiable subtype of schizophrenia

BACKGROUND

Genetic testing in psychiatry promises to improve patient care through advances in personalised medicine. However, there are few clinically relevant examples.

AIMS

To determine whether patients with a well-established genetic subtype of schizophrenia show a different response profile to the antipsychotic clozapine than those with idiopathic schizophrenia.

METHOD

We retrospectively studied the long-term safety and efficacy of clozapine in 40 adults with schizophrenia, half with a 22q11.2 deletion (22q11.2DS group) and half matched for age and clinical severity but molecularly confirmed to have no pathogenic copy number variant (idiopathic group).

RESULTS

Both groups showed similar clinical improvement and significant reductions in hospitalisations, achieved at a lower median dose for those in the 22q11.2DS group. Most common side-effects were similarly prevalent between the two groups, however, half of the 22q11.2DS group experienced at least one rare serious adverse event compared with none of the idiopathic group. Many were successfully retried on clozapine.

CONCLUSIONS

Individuals with 22q11.2DS-schizophrenia respond as well to clozapine treatment as those with other forms of schizophrenia, but may represent a disproportionate number of those with serious adverse events, primarily seizures. Lower doses and prophylactic (for example anticonvulsant) management strategies can help ameliorate side-effect risks. This first systematic evaluation of antipsychotic response in a genetic subtype of schizophrenia provides a proof-of-principle for personalised medicine and supports the utility of clinical genetic testing in schizophrenia.

Burden analysis of rare microdeletions suggests a strong impact of neurodevelopmental genes in genetic generalised epilepsies

Genetic generalised epilepsy (GGE) is the most common form of genetic epilepsy, accounting for 20% of all epilepsies. Genomic copy number variations (CNVs) constitute important genetic risk factors of common GGE syndromes. In our present genome-wide burden analysis, large (≥ 400 kb) and rare (< 1%) autosomal microdeletions with high calling confidence (≥ 200 markers) were assessed by the Affymetrix SNP 6.0 array in European case-control cohorts of 1,366 GGE patients and 5,234 ancestry-matched controls. We aimed to: 1) assess the microdeletion burden in common GGE syndromes, 2) estimate the relative contribution of recurrent microdeletions at genomic rearrangement hotspots and non-recurrent microdeletions, and 3) identify potential candidate genes for GGE. We found a significant excess of microdeletions in 7.3% of GGE patients compared to 4.0% in controls (P = 1.8 x 10-7; OR = 1.9). Recurrent microdeletions at seven known genomic hotspots accounted for 36.9% of all microdeletions identified in the GGE cohort and showed a 7.5-fold increased burden (P = 2.6 x 10-17) relative to controls. Microdeletions affecting either a gene previously implicated in neurodevelopmental disorders (P = 8.0 x 10-18, OR = 4.6) or an evolutionarily conserved brain-expressed gene related to autism spectrum disorder (P = 1.3 x 10-12, OR = 4.1) were significantly enriched in the GGE patients. Microdeletions found only in GGE patients harboured a high proportion of genes previously associated with epilepsy and neuropsychiatric disorders (NRXN1, RBFOX1, PCDH7, KCNA2, EPM2A, RORB, PLCB1). Our results demonstrate that the significantly increased burden of large and rare microdeletions in GGE patients is largely confined to recurrent hotspot microdeletions and microdeletions affecting neurodevelopmental genes, suggesting a strong impact of fundamental neurodevelopmental processes in the pathogenesis of common GGE syndromes.