Deletion Syndrome 22q11.2: A Systematic Review

Review of the Pathophysiology and Clinical Manifestations of 22q11.2 Deletion and Duplication Syndromes

22q11.2 deletion and duplication syndromes are complex genetic syndromes composed of a wide spectrum of clinical manifestations, mostly affecting cardiovascular, endocrine, neurodevelopmental, and immune functioning. 22q11.2 deletion syndrome (22q11.2 DS) is more common and widely recognized compared to the duplication counterpart. Most of the literature focuses on delineating the genetic, molecular, and clinical impact of 22q11.2 DS, and less information focuses on the 22q11.2 duplication syndrome (22q11.2 DupS). We will cover both variants in this review and shed light on the less reported atypical 22q11.2 deletions and duplications. Variants in multiple genes in the 22q11.2 region, especially the TBX1 and DGCR8 genes, have been linked to the clinical phenotypes of 22q11.2 DS and 22q11.2 DupS. Variations in genes on the non-deleted homologous chromosome in the critical 22q11.2 region can further influence phenotypes by revealing recessive diseases. This effect has been documented for several genes in this area, such as SNAP29 and GP1BB. Neural crest development is usually impacted leading to various cardiovascular defects including Tetralogy of Fallot and truncus arteriosus. It can also cause palatal defects, especially velopharyngeal deficiency, considered another hallmark of 22q11DS. Individuals may also present with hypocalcemia and thyroid dysfunction due to impaired parathyroid gland formation and thyroid dysgenesis, respectively. Immunodeficiencies result from impaired T-cell development due to thymic hypoplasia, also a consequence of abnormal neural crest development. Humoral defects are also now increasingly recognized in these individuals. Psychiatric, neurocognitive, and developmental features are common, but severity varies across affected individuals. Other systems like the genitourinary, gastrointestinal, skeletal, and hematological are also involved. Monitoring and treating all the possible clinical manifestations require a multi-disciplinary approach to effectively address the plethora of clinical findings. The complex nature of the treatment guidelines reflects the clinical heterogeneity of these genetic variations. Further research is required to continue exploring the mechanisms relating to the impact of genetic aberrations in the 22q11.2 region on various clinical parameters. This will hopefully guide future updates to the current clinical practice guidelines to continue tailoring them to the individual needs of each affected person.

Benchmarking nanopore sequencing and rapid genomics feasibility: validation at a quaternary hospital in New Zealand

Approximately 200 critically ill infants and children in New Zealand are in high-dependency care, many suspected of having genetic conditions, requiring scalable genomic testing. We adopted an acute care genomics protocol from an accredited laboratory and established a clinical pipeline using Oxford Nanopore Technologies PromethION 2 solo system and Fabric GEM™ software. Benchmarking of the pipeline was performed using Global Alliance for Genomics and Health benchmarking tools and Genome in a Bottle samples (HG002-HG007). Evaluation of single nucleotide variants resulted in a precision and recall of 0.997 and 0.992, respectively. Small indel identification approached a precision of 0.922 and recall of 0.838. Large genomic variations from Coriell Copy Number Variation Reference Panel 1 were reliably detected with ~2 M long reads. Finally, we present results obtained from fourteen trio samples, ten of which were processed in parallel with a clinically accredited short-read rapid genomic testing pipeline (Newborn Genomics Programme; NCT06081075; 2023-10-12).

Mortality in Patients with 22q11.2 Rearrangements

The 22q11.2 region is highly susceptible to genomic rearrangements leading to multiple genomic disorders, including 22q11.2 microdeletion syndrome (22q11.2 DS) (MIM# 188400), 22q11.2 microduplication syndrome (MIM# 608363), supernumerary der(22)t(11;22) syndrome (also known as Emanuel Syndrome; MIM# 609029), and Cat Eye Syndrome (MIM# 115470). In this study, we present data on causes of mortality, average age of death, and the existing associated risk factors in patients with 22q11.2 rearrangements. Our cohort included 223 patients (120 males and 103 females) with confirmed diagnoses of 22q11.2 rearrangements diagnosed through molecular techniques (FISH, MLPA, and CMA). Relatives from patients who have been molecularly confirmed with 22q11.2 rearrangements have also been added to the study, regardless of the presence or absence of symptoms. Of these 223 individuals, 21 (9.4%) died. Deceased patients' rearrangements include 19 microdeletions, 1 microduplication, and 1 patient with a marker chromosome. The median age of death was 3 months and 18 days (ranging from 3 days to 34 years). There were 17 patients who died at pediatric age (80.95%), 3 died at adult age (14.28%), and for 1 of whom, the age of death is unknown (4.76%). Eighteen patients were White Mediterranean (European non-Finnish) (85.71%) whereas three were Amerindian (South American) (14.28%). Mortality from cardiac causes accounted for 71.42%. The second most frequent cause of death was sepsis in two patients (9.52%). One patient died from respiratory failure (4.76%) and one from renal failure (4.76%). Information regarding the cause of death was not available in two patients (9.52%). Most patients who died were diagnosed within the first week of life, the majority on the first day. This study adds additional information on mortality in one of the largest cohorts of patients with 22q11.2 rearrangements in more than 30 years of follow-up.

The Co-Occurrence of 22q11.2 Deletion Syndrome and Epithelial Basement Membrane Dystrophy: A Case Report and Review of the Literature

BACKGROUND

22q11.2 deletion syndrome (22q11.2DS) is a genetic disorder caused by the deletion of the q11.2 band of chromosome 22. It may affect various systems, including the cardiovascular, immunological, gastrointestinal, endocrine, and neurocognitive systems. Additionally, several ocular manifestations have been described.

RESULTS

We report a case of a 34-year-old female diagnosed with 22q11.2DS who presented with visual discomfort and foreign body sensation in both eyes. She had no history of recurrent ocular pain. A comprehensive ophthalmological examination was performed, including anterior segment optical coherence tomography and in vivo confocal microscopy. Overall, the exams revealed bilateral corneal map-like lines, dots, and fingerprint patterns, consistent with a diagnosis of epithelial basement membrane dystrophy (EBMD). In addition to presenting with this novel corneal manifestation for 22q11.2 DS, we review the ocular clinical features of 22q11.2DS in the context of our case.

CONCLUSIONS

The EBMD may represent a new corneal manifestation associated with 22q11.2 syndrome, although the link between these conditions is unknown. Further research is warranted to investigate potentially shared genetic or molecular pathways to the understanding of the phenotypic variety observed among this rare syndrome.

Small Differences and Big Changes: The Many Variables of MicroRNA Expression and Function in the Brain

MicroRNAs are emerging as crucial regulators within the complex, dynamic environment of the synapse, and they offer a promising new avenue for the treatment of neurological disease. These small noncoding RNAs modify gene expression in several ways, including posttranscriptional modulation via binding to complementary and semicomplementary sites on target mRNAs. This rapid, finely tuned regulation of gene expression is essential to meet the dynamic demands of the synapse. Here, we provide a detailed review of the multifaceted world of synaptic microRNA regulation. We discuss the many mechanisms by which microRNAs regulate gene expression at the synapse, particularly in the context of neuronal plasticity. We also describe the various factors, such as age, sex, and neurological disease, that can influence microRNA expression and activity in neurons. In summary, microRNAs play a crucial role in the intricate and quickly changing functional requirements of the synapse, and context is essential in the study of microRNAs and their potential therapeutic applications.

In-silico identification of deleterious non-synonymous SNPs of TBX1 gene: Functional and structural impact towards 22q11.2DS

The TBX1 gene plays a critical role in the development of 22q11.2 deletion syndrome (22q11.2DS), a complex genetic disorder associated with various phenotypic manifestations. In this study, we performed in-silico analysis to identify potentially deleterious non-synonymous single nucleotide polymorphisms (nsSNPs) within the TBX1 gene and evaluate their functional and structural impact on 22q11.2DS. A comprehensive analysis pipeline involving multiple computational tools was employed to predict the pathogenicity of nsSNPs. This study assessed protein stability and explored potential alterations in protein-protein interactions. The results revealed the rs751339103(C>A), rs780800634(G>A), rs1936727304(T>C), rs1223320618(G>A), rs1248532217(T>C), rs1294927055 (C>T), rs1331240435 (A>G, rs1601289406 (A>C), rs1936726164 (G>A), and rs911796187(G>A) with a high-risk potential for affecting protein function and stability. These nsSNPs were further analyzed for their impact on post-translational modifications and structural characteristics, indicating their potential disruption of molecular pathways associated with TBX1 and its interacting partners. These findings provide a foundation for further experimental studies and elucidation of potential therapeutic targets and personalized treatment approaches for individuals affected by 22q11.2DS.

An Unusual Relation in an Infant With Left Hemitruncus and Tetralogy of Fallot Along With Pulmonary Valve Syndrome: A Case Report

The abnormal origin of the left pulmonary artery (LPA) from the ascending aorta is a rare cardiac condition that is often associated with several other congenital defects. In this paper, we report the case of an infant who presented with recurrent infections and was prenatally diagnosed with tetralogy of Fallot (TOF). During echocardiography, various other cardiac defects such as ventricular septal defects (VSD), pulmonary stenosis (PS), and dilated right heart chambers were identified. Furthermore, cardiac catheterization revealed an anomalous origin of the LPA arising from the aorta associated with a narrow pulmonary annulus. Due to both conditions sharing a similar embryological course, the condition is commonly associated with a conotruncal defect known as DiGeorge syndrome. Together, the overall combination of cardiac anomalies is both unusual and unique. This case study explains the clinical associations, embryological origin, and surgical management of this condition in an infant.

Understanding the Variability of 22q11.2 Deletion Syndrome: The Role of Epigenetic Factors

Initially described as a triad of immunodeficiency, congenital heart defects and hypoparathyroidism, 22q11.2 deletion syndrome (22q11.2DS) now encompasses a great amount of abnormalities involving different systems. Approximately 85% of patients share a 3 Mb 22q11.2 region of hemizygous deletion in which 46 protein-coding genes are included. However, the hemizygosity of the genes of this region cannot fully explain the clinical phenotype and the phenotypic variability observed among patients. Additional mutations in genes located outside the deleted region, leading to "dual diagnosis", have been described in 1% of patients. In some cases, the hemizygosity of the 22q11.2 region unmasks autosomal recessive conditions due to additional mutations on the non-deleted allele. Some of the deleted genes play a crucial role in gene expression regulation pathways, involving the whole genome. Typical miRNA expression patterns have been identified in 22q11.2DS, due to an alteration in miRNA biogenesis, affecting the expression of several target genes. Also, a methylation epi-signature in CpG islands differentiating patients from controls has been defined. Herein, we summarize the evidence on the genetic and epigenetic mechanisms implicated in the pathogenesis of the clinical manifestations of 22q11.2 DS. The review of the literature confirms the hypothesis that the 22q11.2DS phenotype results from a network of interactions between deleted protein-coding genes and altered epigenetic regulation.

The Outcomes of Cardiac Surgery in Children With DiGeorge Syndrome in a Single Center Experience: A Retrospective Cohort Study

Background DiGeorge syndrome, a common genetic microdeletion syndrome, is associated with multiple congenital anomalies, including congenital cardiac diseases. This study aims to identify the short and midterm outcomes of cardiac surgery performed on children with DiGeorge syndrome. Methods A retrospective cohort study was conducted between the period of 2018-2022, which included children divided into two groups with a 1:2 ratio. Group one included DiGeorge syndrome patients who were diagnosed using fluorescence in situ hybridization (FISH). Group two included the control group of patients who were clear of genetic syndromes. The two groups were matched based on similar cardiac surgery, age of surgery, and Risk Adjustment in Congenital Heart Surgery (RACHS-1) score. The two groups were compared based on the demographical data and postoperative complications. Results The study consisted of 81 children; 27 were DiGeorge syndrome patients, and 54 were in the control group. DiGeorge syndrome patients showed an increase in mechanical ventilation duration (p=0.0047), intensive care unit (ICU) length of stay (p=0.0012), and hospital length of stay (p=0.0391). Moreover, they showed an increased risk for bacteremia (p=0.0414), ventilator-associated pneumonia (VAP; p=0.0036), urinary tract infections (UTI; p=0.0064), and surgical site infection (SSI; p≤0.0001). They were also more susceptible to postoperative seizures (p=0.0049). Furthermore, patients with DiGeorge syndrome had a higher prevalence of congenital renal anomalies. However, there was no mortality in either group.  Conclusion This study shows a variability in the postoperative outcomes between the two groups. The study demonstrates that patients with DiGeorge syndrome have higher risks of infections and longer hospital stay during the postoperative period. Further research with a larger sample is needed to confirm our findings.

Hypoparathyroidism Associated with Benign Thyroid Nodules in DiGeorge-like Syndrome: A Rare Case Report and Literature Review

BACKGROUND

DiGeorge-like syndrome (DGLS) is a rare genetic disorder due to the presence of the same classical clinical manifestations of DiGeorge syndrome (DGS) without its typical deletion. In the DGLS phenotype, hypoparathyroidism seldom occurs and is considered rare. In DGS, hypocalcemia affects up to 70% of patients, and a considerable share often has asymptomatic thyroid abnormalities.

CASE PRESENTATION

In this study, we describe an unusual case of a 16-year-old patient with DGLS due to a duplication of 365 kb in the 20p11.22 region, affected by hypoparathyroidism associated with thyroid nodule. The intraoperative parathyroid evaluation ruled out agenesis as a cause of hypoparathyroidism. In addition, we carried out a thorough literature review from 2010 to 2023 of DGLS cases using specific keywords, such as "22q11.2 deletion syndrome", "Di- George-like Syndrome", "hypoparathyroidism", "thyroid", and "children", analyzing 119 patients with DGLS.

CONCLUSION

Interestingly enough, the present case represents, to our knowledge, the first report of a patient with DGLS associated with hypoparathyroidism and the presence of thyroid nodules where an intraoperative observation reported a non-functional parathyroid gland.

Navigating the transition of care in patients with inborn errors of immunity: a single-center's descriptive experience

The transition from pediatric to adult care is a critical milestone in managing children, especially in those with complex chronic conditions. It involves ensuring the patient and family adapt correctly to the new phase, maintaining continuity of ongoing treatments, and establishing an appropriate follow-up plan with specialists. Patients with Inborn error of immunity (IEI), formerly known as Primary Immune Disorders (PID) are part of a group of disorders characterized by alterations in the proper functioning of the immune system; as the diagnostic and treatment tools for these entities progress, life expectancy increases, and new needs emerge. These children have special needs during the transition. Particularly important in the group of children with PID and syndromic features, who often present multiple chronic medical conditions. In these cases, transition planning is a significant challenge, involving not only the patients and their families but also a wide range of specialists. To achieve this, a multidisciplinary transition team should be established between the pediatric specialists and the adult consultants, designing a circuit in which communication is essential. As few transition care guidelines in the field of PID are available, and to our knowledge, there is no specific information available regarding patients with PID associated with syndromic features, we share our experience in this issue as a Primary Immunodeficiencies Unit that is a National Reference Center for PID, and propose a guide to achieve an adequate and successful transition to adulthood in these patients, especially in those with associated syndromic features.

A Novel Distal 22Q11.21 Microduplication in a 43-Year-Old Male Patient with Mild Intellectual Disability, Social Cognitive Dysfunctions, and Anxiety

OBJECTIVE

The chromosome region 22q11.2 is highly susceptible to genomic rearrangements. It has become clear that genomic instability extends distally to the commonly deleted/duplicated region (Low Copy Repeats [LCR] A-D) and that a clear difference exists between the phenotypic presentation of patients with rearrangements in the common region versus that in the distal region (LCR D-H), particularly with respect to developmental and somatic issues. Microdeletions in the 22q11.2 distal region are typically associated with congenital heart defects whereas distal 22q11.2 microduplications are infrequently described and present with a smaller duplicated region and a rather unspecified phenotype.

METHOD

The present paper provides detailed assessments of a middle-aged male with mild intellectual disability, elsewhere diagnosed with autism spectrum disorder. Because of persisting functional complaints, he was referred for second opinion to a specialized outpatient department.

RESULTS

High resolution SNP-based array analysis demonstrated a ~1.5 Mb distal microduplication in chromosome 22 flanked by LCR region 22C and LCR22E encompassing among others the disease gene MAPK1. No remarkable facial dysmorphisms were noticed. Autism spectrum disorder was ruled out and it was concluded that the patient was primarily suffering from mild intellectual disability and social cognitive dysfunctions with anxieties and suspicious social interactions, to be understood as a disorder within the anxiety spectrum.

CONCLUSIONS

The pattern of psychological and psychiatric phenomena was discussed against the background of findings on psychopathology in the chromosome 22 region demarcated by LCR breakpoints C and E. It was suggested that alterations in the MAPK1 gene due to either a deletion or a duplication enhance the vulnerability to develop a psychiatric disorder within the anxiety spectrum.

Skeletal system in adult congenital heart disease

Image 1.

Clinical Course and Outcome of Prenatally Detected 22q11.2 Deletion Syndrome-A Retrospective Analysis

The 22q11.2 deletion syndrome (22q11.2 DS) is known as the most common microdeletion syndrome. Due to its variable clinical phenotype, prenatal diagnosis can be challenging. The aim of this retrospective study was to evaluate the clinical course and pregnancy outcome of cases with prenatally diagnosed 22q11.2 deletion syndrome (DS) as well as to evaluate the role of prenatal magnetic resonance imaging (MRI) and postmortem examination. In total, 21 cases who underwent prenatal ultrasound examination and pregnancy care at the Department of Obstetrics and Gynecology at the Medical University of Vienna between 2012 and 2022 were included. The majority of the cases were genetically diagnosed using fluorescent in situ hybridization (FISH). The median gestational age (GA) at genetic diagnosis was 23.0 weeks (IQR 21.4-24.8 weeks). CHDs were detected in all fetuses and the most common extracardiac manifestation was thymus hypo/aplasia followed by genitourinary anomalies. Prenatal magnetic resonance imaging (MRI) revealed additional diagnostic information in three of ten cases. Overall, 14 patients opted for drug-induced TOP, of which 9 cases had a feticide prior to the induction of labor. The majority of craniofacial malformations were only detected by autopsy. In conclusion, the majority of cases prenatally diagnosed with 22q11.2 DS had an absent or hypoplastic thymus noted antenatally in addition to the detected CHD, and almost half of the cases had another extracardiac malformation of predominantly genitourinary origin. Furthermore, prenatal MRIs confirmed previously detected malformations, but only provided additional diagnostic information in three out of ten cases, whereas postmortem examination diagnosed most of the craniofacial anomalies and should always be conducted, serving as an important quality indicator for prenatal imaging.

Chromosome 22q11.2 Deletion Syndrome: A Comprehensive Review of Molecular Genetics in the Context of Multidisciplinary Clinical Approach

The 22q11.2 deletion syndrome is a multisystemic disorder characterized by a marked variability of phenotypic features, making the diagnosis challenging for clinicians. The wide spectrum of clinical manifestations includes congenital heart defects-most frequently conotruncal cardiac anomalies-thymic hypoplasia and predominating cellular immune deficiency, laryngeal developmental defects, midline anomalies with cleft palate and velar insufficiency, structural airway defects, facial dysmorphism, parathyroid and thyroid gland hormonal dysfunctions, speech delay, developmental delay, and neurocognitive and psychiatric disorders. Significant progress has been made in understanding the complex molecular genetic etiology of 22q11.2 deletion syndrome underpinning the heterogeneity of clinical manifestations. The deletion is caused by chromosomal rearrangements in meiosis and is mediated by non-allelic homologous recombination events between low copy repeats or segmental duplications in the 22q11.2 region. A range of genetic modifiers and environmental factors, as well as the impact of hemizygosity on the remaining allele, contribute to the intricate genotype-phenotype relationships. This comprehensive review has been aimed at highlighting the molecular genetic background of 22q11.2 deletion syndrome in correlation with a clinical multidisciplinary approach.

Congenital Athymia: Unmet Needs and Practical Guidance

Inborn errors of thymic stromal cell development and function which are associated with congenital athymia result in life-threatening immunodeficiency with susceptibility to infections and autoimmunity. Athymic patients can be treated by thymus transplantation using cultured donor thymus tissue. Outcomes in patients treated at Duke University Medical Center and Great Ormond Street Hospital (GOSH) over the past three decades have shown that sufficient T-cell immunity can be recovered to clear and prevent infections, but post-treatment autoimmune manifestations are relatively common. Whilst thymus transplantation offers the chance of long-term survival, significant challenges remain to optimise the outcomes for the patients. In this review, we will discuss unmet needs and offer practical guidance based on the experience of the European Thymus Transplantation programme at GOSH. Newborn screening (NBS) for severe combined immunodeficiency (SCID) and routine use of next-generation sequencing (NGS) platforms have improved early recognition of congenital athymia and increasing numbers of patients are being referred for thymus transplantation. Nevertheless, there remain delays in diagnosis, in particular when the cause is genetically undefined, and treatment accessibility needs to be improved. The majority of athymic patients have syndromic features with acute and chronic complex health issues, requiring life-long multidisciplinary and multicentre collaboration to optimise their medical and social care. Comprehensive follow up after thymus transplantation including monitoring of immunological results, management of co-morbidities and patient and family quality-of-life experience, is vital to understanding long-term outcomes for this rare cohort of patients. Alongside translational research into improving strategies for thymus replacement therapy, patient-focused clinical research will facilitate the design of strategies to improve the overall care for athymic patients.

Non-Invasive Prenatal Testing in Germany

In the short 10 years following the introduction of non-invasive prenatal testing (NIPT), it has been adapted in many countries around the world as a standard screening test. In this review, this development was analyzed with a special focus on Germany. As a result, it can be stated that all known advantages of NIPT apart from "compensating for having no access to centers offering invasive diagnostics" are valid for Germany. In addition, following a review of the international literature, all documented issues with NIPT are also observed in Germany. However, the German Gene Diagnostics Act (GenDG) addresses a number of these issues, for example, the regulations by GenDG hamper induced abortions, based exclusively on an abnormal NIPT result. At the same time, GenDG has created new problems, as a possible collusion between the "right not to know with regard to parts of the examination result" may occur, or that the sex of the fetus must not be reported to the pregnant woman before the 12th week of gestation. Main conclusions drawn are that appropriate training and the continuing education of the physicians providing NIPT-related counseling are needed, as well as the provision of balanced and comprehensive information for the pregnant woman or the couple that is imperative.