Immunologic features of chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

Genetic profile of a large Spanish cohort with hypercalcemia

Introduction

The disorders in the metabolism of calcium can present with manifestations that strongly suggest their diagnosis; however, most of the time, the symptoms with which they are expressed are nonspecific or present only as a laboratory finding, usually hypercalcemia. Because many of these disorders have a genetic etiology, in the present study, we sequenced a selection of 55 genes encoding the principal proteins involved in the regulation of calcium metabolism.

Methods

A cohort of 79 patients with hypercalcemia were analyzed by next-generation sequencing.

Results

The 30% of our cohort presented one pathogenic or likely pathogenic variant in genes associated with hypercalcemia. We confirmed the clinical diagnosis of 17 patients with hypocalciuric hypercalcemia (pathogenic or likely pathogenic variants in the CASR and AP2S1 genes), one patient with neonatal hyperparathyroidism (homozygous pathogenic variant in the CASR gene), and another patient with infantile hypercalcemia (two pathogenic variants in compound heterozygous state in the CYP24A1 gene). However, we also found variants in genes associated with primary hyperparathyroidism (GCM2), renal hypophosphatemia with or without rickets (SLC34A1, SLC34A3, SLC9A3R1, VDR, and CYP27B1), DiGeorge syndrome (TBX1 and NEBL), and hypophosphatasia (ALPL). Our genetic study revealed 11 novel variants.

Conclusions

Our study demonstrates the importance of genetic analysis through massive sequencing to obtain a clinical diagnosis of certainty. The identification of patients with a genetic cause is important for the appropriate treatment and identification of family members at risk of the disease.

Th1/interferon-γ bias in 22q11.2 deletion syndrome is driven by memory T cells and exacerbated by IL-7

The aim of this study was to investigate the impact of thymic dysplasia on the phenotypic and functional characteristics of T cells in patients with 22q11.2 deletion syndrome, including T-cell phenotype, transcriptional profile, cytokine production, as well as the possibility of utilizing IL-7 to recover their numbers and function. We found a strong bias towards Th1 response in pediatric and young adult 22q11.2DS patients, expansion of CXCR5+ follicular helper cells and CXCR3+CCR6- Th1 cells, increased production of cytokines IFN-γ, IL-10, IL-2, IL-21 and TNF-α. This Th1 skew was primarily driven by expanded terminally differentiated T cells. IL-7 further reduced naive T cells, increased cytokine production and caused an upregulation of exhaustion markers. Thus, Th1 bias in T cell populations persists from infancy into adolescence and is accompanied by accelerated maturation of T cells into memory stages. This phenotype is exacerbated by IL-7 which causes further decrease in naïve T cells in vitro.

Risk of thyroid neoplasms in patients with 22q11.2 deletion and DiGeorge-like syndromes: an insight for follow-up

Introduction

The chromosome 22q11.2 deletion syndrome comprises phenotypically similar diseases characterized by abnormal development of the third and fourth branchial arches, resulting in variable combinations of congenital heart defects, dysmorphisms, hypocalcemia, palatal dysfunction, developmental or neuropsychiatric disorders, and impairment of the immune system due to thymic dysfunction. Other genetic syndromes, often called DiGeorge-like, share clinical and immunological features with 22q11.2 deletion syndrome. This syndrome has been rarely associated with malignancies, mainly hematological but also hepatic, renal, and cerebral. Rarely, malignancies in the head and neck region have been described, although no aggregate of data on the development of thyroid neoplasms in patients with this clinical phenotype has been conducted so far.

Materials and methods

To characterize this possible association, a multicenter survey was made. Thus, we present a case series of five pediatric patients with 22q11.2 deletion syndrome or DiGeorge-like syndrome who were occasionally found with confirmed or highly suspected neoplasms of the thyroid gland during their follow-up. In three cases, malignancies were histologically confirmed, but their outcome was good due to an early recognition of suspicious nodules and precocious surgery.

Conclusions

This study underlines for clinicians the higher risk of neoplasms in the head and neck district for patients affected by these syndromes. It also emphasizes the importance of a prolonged clinical and ultrasound follow-up for patients with this clinical and immunological phenotype.

Chromosome 22q11.2 Deletion (DiGeorge Syndrome): Immunologic Features, Diagnosis, and Management

PURPOSE OF REVIEW

This review focuses on immunologic findings, relationships among immunologic findings and associated conditions of autoimmunity and atopy, and management of immunologic disease in chromosome 22q11.2 deletion syndrome (22q11.2DS, historically known as DiGeorge syndrome).

RECENT FINDINGS

The implementation of assessment of T cell receptor excision circles (TRECs) in newborn screening has led to increased detection of 22q11.2 deletion syndrome. While not yet applied in clinical practice, cell-free DNA screening for 22q11.2DS also has the potential to improve early detection, which may benefit prompt evaluation and management. Multiple studies have further elucidated phenotypic features and potential biomarkers associated with immunologic outcomes, including the development of autoimmune disease and atopy. The clinical presentation of 22q11.2DS is highly variable particularly with respect to immunologic manifestations. Time to recovery of immune system abnormalities is not well-defined in current literature. An understanding of the underlying causes of immunologic changes found in 22q11.2DS, and the progression and evolution of immunologic changes over the lifespan have expanded over time and with improved survival. An included case highlights the variability of presentation and potential severity of T cell lymphopenia in partial DiGeorge syndrome and demonstrates successful spontaneous immune reconstitution in partial DiGeorge syndrome despite initial severe T cell lymphopenia.

Analyses of thymocyte commitment to regulatory T cell lineage in thymus of healthy subjects and patients with 22q11.2 deletion syndrome

The Chromosome 22q11.2 deletion syndrome (22q11.2DS) results in an inborn error of immunity due to defective thymic organogenesis. Immunological abnormalities in 22q11.2DS patients are thymic hypoplasia, reduced output of T lymphocytes by the thymus, immunodeficiency and increased incidence of autoimmunity. While the precise mechanism responsible for increased incidence of autoimmunity is not completely understood, a previous study suggested a defect in regulatory T cells (Treg) cell lineage commitment during T cell development in thymus. Here, we aimed to analyze this defect in more detail. Since Treg development in human is still ill-defined, we first analyzed where Treg lineage commitment occurs. We performed systematic epigenetic analyses of the Treg specific demethylation region (TSDR) of the FOXP3 gene in sorted thymocytes at different developmental stages. We defined CD3+CD4+CD8+ FOXP3+CD25+ as the T cell developmental stage in human where TSDR demethylation first occurs. Using this knowledge, we analyzed the intrathymic defect in Treg development in 22q11.2DS patients by combination of TSDR, CD3, CD4, CD8 locus epigenetics and multicolor flow cytometry. Our data showed no significant differences in Treg cell frequencies nor in their basic phenotype. Collectively, these data suggest that although 22q11.2DS patients present with reduced thymic size and T cell output, the frequencies and the phenotype of Treg cell at each developmental stage are surprisingly well preserved.

Infections in Inborn Errors of Immunity with Combined Immune Deficiency: A Review

Enhanced susceptibility to microbes, often resulting in severe, intractable and frequent infections due to usually innocuous organisms at uncommon sites, is the most striking feature in individuals with an inborn error of immunity. In this narrative review, based on the International Union of Immunological Societies' 2022 (IUIS 2022) Update on phenotypic classification of human inborn errors of immunity, the focus is on commonly encountered Combined Immunodeficiency Disorders (CIDs) with susceptibility to infections. Combined immune deficiency disorders are usually commensurate with survival beyond infancy unlike Severe Combined Immune Deficiency (SCID) and are often associated with clinical features of a syndromic nature. Defective humoral and cellular immune responses result in susceptibility to a broad range of microbial infections. Although disease onset is usually in early childhood, mild defects may present in late childhood or even in adulthood. A precise diagnosis is imperative not only for determining management strategies, but also for providing accurate genetic counseling, including prenatal diagnosis, and also in deciding empiric treatment of infections upfront before investigation reports are available.

Immunologic, Molecular, and Clinical Profile of Patients with Chromosome 22q11.2 Duplications

PURPOSE

Duplication of chromosome 22q11.2 due to meiotic non-allelic homologous recombination results in a distinct syndrome, chromosome 22q11.2 duplication syndrome that has some overlapping phenotypic features with the corresponding 22q11.2 deletion syndrome. Literature on immunologic aspects of the duplication syndrome is limited. We conducted a retrospective study of 216 patients with this syndrome to better define the key features of the duplication syndrome.

METHODS

Single-center retrospective record review was performed. Data regarding demographics, clinical details, and immunological tests were compiled, extracted into a predetermined data collection form, and analyzed.

RESULTS

This cohort comprised 113 (52.3%) males and 103 (47.7%) females. The majority (54.6%) of mapped duplications were between low copy repeat regions A-D (LCR22A to -D). Though T cell subsets were relatively preserved, switched memory B cells, immunoglobulins, and specific antibodies were each found to be decreased in a subset of the cohort. One-fifth (17/79, 21.5%) of patients had at least 2 low immunoglobulin values, and panhypogammaglobulinemia was found in 11.7% (9/79) cases. Four children were on regular immunoglobulin replacement therapy. Asthma and eczema were the predominant atopic symptoms in our cohort.

CONCLUSION

Significant immunodeficiencies were observed in our cohort, particularly in B cells and antibodies. Our study expands the current clinical understanding and emphasizes the need of immunological studies and multidisciplinary approaches for these patients.

Clinical Practice Guidelines for the Immunological Management of Chromosome 22q11.2 Deletion Syndrome and Other Defects in Thymic Development

Current practices vary widely regarding the immunological work-up and management of patients affected with defects in thymic development (DTD), which include chromosome 22q11.2 microdeletion syndrome (22q11.2del) and other causes of DiGeorge syndrome (DGS) and coloboma, heart defect, atresia choanae, retardation of growth and development, genital hypoplasia, ear anomalies/deafness (CHARGE) syndrome. Practice variations affect the initial and subsequent assessment of immune function, the terminology used to describe the condition and immune status, the accepted criteria for recommending live vaccines, and how often follow-up is needed based on the degree of immune compromise. The lack of consensus and widely varying practices highlight the need to establish updated immunological clinical practice guidelines. These guideline recommendations provide a comprehensive review for immunologists and other clinicians who manage immune aspects of this group of disorders.

COVID-19 Severity, Cardiological Outcome, and Immunogenicity of mRNA Vaccine on Adult Patients With 22q11.2 DS

BACKGROUND

The contemporaneous presence of immune defects and heart diseases in patients with 22q11.2 deletion syndrome (22q11.3DS) might represent risk factors for severe coronavirus 2019 disease (COVID-19).

OBJECTIVE

To analyze severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outcome in 22q11.2DS patients and immunogenicity of different doses of mRNA SARS-CoV-2 vaccine.

METHODS

Longitudinal observational study on SARS-CoV-2 outcome in 60 adults with 22q11.2DS (March 2020-June 2022). Anti-Spike, and anti-receptor binding domain (RBD) antibody responses, generation of Spike-specific memory B cells (MBCs) and Spike-specific T cells at different time points before and after the mRNA BNT162b2 vaccination were evaluated in 16 22q11.2DS patients.

RESULTS

We recorded a 95% rate of vaccination, with almost all patients being immunized with the booster dose. Twenty-one patients had SARS-CoV-2 infection. Three patients were infected before vaccine availability, 6 after receiving 2 doses of vaccine, and 12 after one booster dose. The SARS-CoV-2- infection had a mild course, except in one unvaccinated patient with several comorbidities who died from acute respiratory distress syndrome (fatality rate 5%). Infected patients had more frequently moderate/severe intellectual disability, lymphopenia, and lower CD4+ count. Despite major congenital heart diseases, COVID-19 did not impact cardiological conditions. The BNT162b2 vaccine induced S1-immunoglobulin G (IgG) responses, low serum S1-IgA, and slightly impaired specific MBCs response. Specific T-cell responses observed were related to lymphocytes and CD4+ T cell counts.

CONCLUSIONS

The SARS-CoV-2 infection had a mild course in most patients with 22q11.2DS, even in patients with major cardiovascular diseases. Immunization induced Spike-specific IgG responses and generated specific MBCs and memory T cells. The weaker memory responses in patients with lymphopenia suggested the need for additional doses.

Immune status of the murine 22q11.2 deletion syndrome model

Mice modeling the hemizygous deletion of chromosome 22q11.2 (22qMc) have been utilized to address various clinical phenotypes associated with the disease, including cardiac malformations, altered neural circuitry, and behavioral deficits. Yet, the status of the T cell compartment, an important clinical concern among 22q11.2 deletion syndrome (22qDS) patients, has not been addressed. While infancy and early childhood in 22qDS are associated with deficient T cell numbers and thymic hypoplasia, which can be severe in a small subset of patients, studies suggest normalization of the T cell counts by adulthood. We found that adult 22qMc do not exhibit thymic hypoplasia or altered thymic T cell development. Our findings that immune cell counts and inflammatory T cell activation are unaffected in 22qMc lend support to the hypothesis that human 22qDS immunodeficiencies are secondary to thymic hypoplasia, rather than intrinsic effects due to the deletion. Furthermore, the 22q11.2 deletion does not impact the differentiation capacity of T cells, nor their activity and response during inflammatory activation. Thus, 22qMc reflects the T cell compartment in adult 22qDS patients, and our findings suggest that 22qMc may serve as a novel model to address experimental and translational aspects of immunity in 22qDS.

Characterization of Autoimmune Thyroid Disease in a Cohort of 73 Paediatric Patients Affected by 22q11.2 Deletion Syndrome: Longitudinal Single-Centre Study

Background. Chromosome 22q11.2 Deletion Syndrome (22q11.2DS) is the most frequent microdeletion syndrome and is mainly characterized by congenital cardiac defects, dysmorphic features, hypocalcemia, palatal dysfunction, developmental delay, and impaired immune function due to thymic hypoplasia or aplasia. Thyroid anomalies are frequently reported in patients with 22q11.2DS, although only a few well-structured longitudinal studies about autoimmune thyroid disease (ATD) have been reported. Aim. To longitudinally evaluate the frequency of thyroid anomalies and ATD in patients with 22q11.2DS. Patients and Methods. Pediatric patients with a confirmed genetic diagnosis of 22q11.2DS were recruited and followed up on longitudinally. Clinical, biochemical, and immunological data were collected, as well as thyroid function, autoimmunity, and thyroid sonographic data. Results. The study included 73 children with 22q11.2DS, with a mean follow-up duration of 9.51 ± 5.72 years. In all, 16 of the 73 enrolled patients (21.9%) developed ATD before 18 years of age (mean age 12.92 ± 3.66 years). A total of 20.5% developed Hashimoto’s Thyroiditis (HT), of whom 50% required L-thyroxine treatment; 1.4% developed Graves Disease. Thyroid hypoplasia was found in 6/16 patients with ATD and left lobe hypoplasia in 9/16 patients. These features were also found in patients affected by 22q11.2DS without ATD. Among patients who developed ATD, at the first altered ultrasound scan, the most frequent anomalies suggestive of thyroiditis were inhomogeneous echotexture, diffuse or irregular hypo-echogenicity, and vascular overflow. Conclusion. We strongly recommend periodic screening of thyroid function and for autoimmunity in patients affected by 22q11.2DS. Along with blood tests, ultrasound scans of the thyroid gland should be performed periodically since some patients who go on to develop an ATD could have specific anomalies on ultrasound prior to any other anomaly.

Case Report: Balanced Reciprocal Translocation t (17; 22) (p11.2; q11.2) and 10q23.31 Microduplication in an Infertile Male Patient Suffering From Teratozoospermia

Two chromosomal abnormalities are described in an infertile man suffering from teratozoospermia: balanced reciprocal translocation t (17; 22) (p11.2; q11.2) and a microduplication in the region 10q23.31. Twenty genes located on the breakpoints of translocation (e.g., ALKBH5, TOP3A, SPECC1L, and CDC45) are selected due to their high expression in testicular tissues and might be influenced by chromosome translocation. Four genes located on the breakpoints of microduplication including FLJ37201, KIF20B, LINC00865, and PANK1 result in an increased dosage of genes, representing an imbalance in the genome. These genes have been reported to be associated with developmental disorders/retardation and might be risk factors affecting spermatogenesis. Bioinformatics analysis is carried out on these key genes, intending to find the pathogenic process of reproduction in the context of the translocation and microduplication encountered in the male patient. The combination of the two chromosomal abnormalities carries additional risks for gametogenesis and genomic instability and is apparently harmful to male fertility. Overall, our findings could contribute to the knowledge of male infertility caused by genetic factors.

Evaluation of rotavirus vaccine administration among a 22q11.2DS patient population

Background

22q11.2 Deletion Syndrome (22q11.2DS) can result in array of congenital abnormalities including immune dysfunction. International guidelines recommend immune evaluation of 22q11.2DS patients prior to live vaccine administration. A rotavirus vaccination program for infants aged 2 and 4 months was implemented in British Columbia (BC) in 2012. Adherence to immune workup recommendations prior to 2 months of age in patients with 22q11.2DS and adverse events following immunization is not known.

Methods

A retrospective chart review of children diagnosed with 22q11.2DS in BC from January 1, 2012 to January 1, 2019 was conducted. Demographic, clinical, laboratory, immunization data and adverse reactions to vaccines were obtained. International guidelines were used as a reference for adherence to immunologic workup recommendations.

Results

Forty-two children with 22q11.2DS were included. Immunization records were available for 39 children, and 22 (52.3%) received at least one dose of a live rotavirus vaccine. No adverse events following immunization were noted in clinical records. While 25 out of 27 (92.6%) of patients who received an immunological workup had a CD4 + lymphocyte count to qualify for safe administration of a live vaccination, only 12 (44%) received the Rotavirus vaccine. Of 22 infants diagnosed with 22q11.DS prior to 8 weeks of age, only ten (45.5%) received an immune workup before the rotavirus vaccine.

Conclusions

The majority of our infant cohort did not receive medical care consistent with international 22q11.2DS vaccination and immunological surveillance recommendations. More effective dissemination of 22q11.2DS guidelines and improved immunological assessment for infants with 22q11.2DS in BC is necessary.

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.

Immunity and inflammation: the neglected key players in congenital heart disease?

Although more than 90% of children born with congenital heart disease (CHD) survive into adulthood, patients face significantly higher and premature morbidity and mortality. Heart failure as well as non-cardiac comorbidities represent a striking and life-limiting problem with need for new treatment options. Systemic chronic inflammation and immune activation have been identified as crucial drivers of disease causes and progression in various cardiovascular disorders and are promising therapeutic targets. Accumulating evidence indicates an inflammatory state and immune alterations in children and adults with CHD. In this review, we highlight the implications of chronic inflammation, immunity, and immune senescence in CHD. In this context, we summarize the impact of infant open-heart surgery with subsequent thymectomy on the immune system later in life and discuss the potential role of comorbidities and underlying genetic alterations. How an altered immunity and chronic inflammation in CHD influence patient outcomes facing SARS-CoV-2 infection is unclear, but requires special attention, as CHD could represent a population particularly at risk during the COVID-19 pandemic. Concluding remarks address possible clinical implications of immune changes in CHD and consider future immunomodulatory therapies.

Transcriptomic profiling of whole blood in 22q11.2 reciprocal copy number variants reveals that cell proportion highly impacts gene expression

22q11.2 reciprocal copy number variants (CNVs) offer a powerful quasi-experimental "reverse-genetics" paradigm to elucidate how gene dosage (i.e., deletions and duplications) disrupts the transcriptome to cause further downstream effects. Clinical profiles of 22q11.2 CNV carriers indicate that disrupted gene expression causes alterations in neuroanatomy, cognitive function, and psychiatric disease risk. However, interpreting transcriptomic signal in bulk tissue requires careful consideration of potential changes in cell composition. We first characterized transcriptomic dysregulation in peripheral blood from reciprocal 22q11.2 CNV carriers using differential expression analysis and weighted gene co-expression network analysis (WGCNA) to identify modules of co-expressed genes. We also assessed for group differences in cell composition and re-characterized transcriptomic differences after accounting for cell type proportions and medication usage. Finally, to explore whether CNV-related transcriptomic changes relate to downstream phenotypes associated with 22q11.2 CNVs, we tested for associations of gene expression with neuroimaging measures and behavioral traits, including IQ and psychosis or ASD diagnosis. 22q11.2 deletion carriers (22qDel) showed widespread expression changes at the individual gene as well as module eigengene level compared to 22q11.2 duplication carriers (22qDup) and controls. 22qDup showed increased expression of 5 genes within the 22q11.2 locus, and CDH6 located outside of the locus. Downregulated modules in 22qDel implicated altered immune and inflammatory processes. Celltype deconvolution analyses revealed significant differences between CNV and control groups in T-cell, mast cell, and macrophage proportions; differential expression of individual genes between groups was substantially attenuated after adjusting for cell composition. Individual gene, module eigengene, and cell proportions were not significantly associated with psychiatric or neuroanatomic traits. Our findings suggest broad immune-related dysfunction in 22qDel and highlight the importance of understanding differences in cell composition when interpreting transcriptomic changes in clinical populations. Results also suggest novel directions for future investigation to test whether 22q11.2 CNV effects on macrophages have implications for brain-related microglial function that may contribute to psychiatric phenotypes in 22q11.2 CNV carriers.

Plasma cells are essentially absent in the luminal gastrointestinal tract of patients with "complete" 22q11.2 deletion syndrome (DiGeorge syndrome)

Gastrointestinal symptoms are commonly reported in patients with 22q11.2 deletion syndrome or DiGeorge syndrome (DGS) in addition to the dominant cardiac manifestations and immunodeficiency. But literature providing specific morphologic details of the gastrointestinal tract pathology is very limited. Here, we provide the first comprehensive morphologic description of the luminal gastrointestinal tract changes in patients with DGS. Cytogenetically confirmed DGS patients were identified, clinical and laboratory data were reviewed to determine the severity of immunodeficiency, and patients were stratified into mildly immunocompromised, that is, partial DiGeorge anomaly or severely immunosuppressed, that is, complete DiGeorge anomaly groups. Gastrointestinal tract biopsies from these patients were retrospectively reviewed and compared with those from controls without the history of DGS. Patients with immunosuppressed DGS showed a near complete absence of plasma cells in the stomach, duodenum, and colon lamina propria by hematoxylin and eosin evaluation. Immunohistochemistry for CD138 used to highlight plasma cells confirmed this finding. The notable absence of plasma cells adds to the existing knowledge of the pathophysiology underlying DGS and expands the differential diagnostic considerations for this finding, which has been previously described in common variable immunodeficiency. It also provides a useful morphologic marker observable by the readily accessible light microscopy. Second, patients with DGS showed a mild increase in epithelial cell apoptosis in their colon. This finding is significant because of its overlap with morphologic features of gastrointestinal graft versus host disease as thymus transplantation is being used as a treatment option for patients with complete DGS.

Clinical Features in a Large Cohort of Patients With 22q11.2 Deletion Syndrome

OBJECTIVES

To evaluate various clinical aspects, specifically regarding immune status, in a large cohort of patients with DiGeorge syndrome.

STUDY DESIGN

Data were collected for 98 patients with DiGeorge syndrome treated at a tertiary medical center. This included general information, laboratory results, and clinical features.

RESULTS

The median age at diagnosis was 2.0 years (range, 0.0-36.5 years). The most common symptoms that led to diagnosis were congenital heart defect, speech delay, palate anomalies, and developmental delay. Common clinical features included recurrent infections (76 patients), congenital heart diseases (61 patients), and otorhinolaryngology disorders (61 patients). Twenty patients had anemia; the incidence was relatively high among patients aged 6-59 months. Thrombocytopenia was present in 20 patients. Recurrent chest infections were significantly higher in patients with T cell and T cell subset deficiencies. Decreased T cell receptor excision circles were more common with increasing age (P < .001). Of the 27 patients hospitalized due to infection, pneumonia was a leading cause in 13.

CONCLUSIONS

Awareness of DiGeorge syndrome's typical and uncommon characteristics is important to improve diagnosis, treatment, surveillance, and follow-up.

Medical and dental characteristics of children with chromosome 22q11.2 deletion syndrome at the Royal Children's Hospital, Melbourne

BACKGROUND

Chromosome 22q11.2 deletion syndrome (22q11.2DS) is a multifaceted syndrome with a variable phenotype. Few studies have described the associated dental characteristics and their relationship with medical co-morbidities; and no Australian data exist.

AIM

To determine the clinical manifestations and correlations between oral and medical conditions in children with 22q11.2DS.

DESIGN

A retrospective observational study. Children genetically diagnosed with 22q11.2DS at the Royal Children's Hospital Melbourne were selected; their medical and dental characteristics were collated and analysed.

RESULTS

The study population (n = 57; mean age 11.5 years, range 2-27 years) experienced a range of medical conditions involving multiple medical systems; of whom 44 (77.2%) had caries experience, 7 (12.3%) developmentally missing teeth, and 31 (54.4%) developmental defects of enamel (DDE). Smaller proportions of primary teeth were affected by DDE in children with congenital heart disease (2.2% vs 9.7%; P = .02), and cardiac surgery (0.2% vs 9%; P = .001). Conversely, children with hypoparathyroidism (n = 2) had significantly higher proportions of primary teeth affected by DDE (27.5% vs 4%; P = .02).

CONCLUSIONS

Significant associations existed between medical conditions (congenital heart disease, history of cardiac surgery, and hypoparathyroidism) and primary dentition DDE in children with 22q11.2 DS.

Accelerated Maturation, Exhaustion, and Senescence of T cells in 22q11.2 Deletion Syndrome

PURPOSE

22q11.2 deletion syndrome (22q11.2DS) is a primary immunodeficiency characterized chiefly by the hypoplasia of the thymus resulting in T cell lymphopenia, increased susceptibility to infections, and higher risk of autoimmune diseases. The irregular thymic niche of T cell development may contribute to autoimmune and atopic complications, whereas the compensatory mechanism of homeostatic T cell proliferation and continuous immune stimulation may result in T cell senescence and exhaustion, further aggravating the immune system dysregulation.

METHODS

We used flow cytometry to investigate T cell maturation, delineation, proliferation, activation, and expression of senescence and exhaustion-associated markers (PD1, KLRG1, CD57) in 17 pediatric and adolescent patients with 22q11.2DS and age-matched healthy donors.

RESULTS

22q11.2DS patients aged 0-5 years had fewer naïve but more effector memory T cells with a tendency to approach normal values with increasing age. Young patients in particular had a higher percentage of proliferating T cells and increased expression of PD1, KLRG1, and CD57, as well as cells co-expressing several exhaustion-associated molecules (PD1, KLRG1, Tbet, Eomes, Helios). Additionally, high-risk 22q11.2DS patients with very low numbers of CD4 T cells had significantly higher percentage of Th1 and Th17 T cells, driven in part by higher proportion of mature T cell forms.

CONCLUSION

The low thymic output and accelerated T cell differentiation remain the principal features of 22q11.2DS patient immunity, especially in young patients of < 5 years. Later in life, homeostatic proliferation drives expression of T cell exhaustion and senescence-associated markers, suggesting functional aberrations in addition to numeric T cell deficiency.

Central 22q11.2 deletion (LCR22 B-D) in a fetus with severe fetal growth restriction and a mother with severe systemic lupus erythematosus: Further evidence of CRKL haploinsufficiency in the pathogenesis of 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2 DS, MIM #188400) is the most common chromosomal microdeletion with an incidence of 1 in 4000 live births. 22q11.2 DS patients present with varying penetrance and a broad phenotypic spectrum including dysmorphic features, congenital heart defects, hypoplastic thymus and T-cell deficiency, and hypocalcemia. The typical deletion spans 3 Mb between 4 large blocks of repetitive DNA, known as low copy repeats (LCRs), on chromosome 22 (LCR22) A and D. This deletion is found in ~85% of 22q11.2 DS patients, while only 4-5% have central LCR22B-D (1.5 Mb) and LCR22C-D (0.7 Mb) deletions. We report on a prenatally diagnosed, inherited case of central LCR22B-D 22q11.2 DS, born to a 22-year-old female with multiple autoimmune disorders. These include Sjogren's-syndrome-related antigen A (SSA+) severe systemic lupus erythematosus (SLE) with cutaneous and discoid components and seronegative antiphospholipid syndrome. Amniocentesis was performed due to fetal growth restriction (FGR). FISH with TUPLE1 (HIRA) probe was normal; however, chromosomal microarray identified a ~737 kb heterozygous loss between LCR22B-D. Subsequently, the same deletion was identified in the mother, which included CRKL and 19 other genes but excluded HIRA and TBX1, the typical candidate genes for 22q11.2DS pathogenesis. This case explores how loss of CRKL may contribute to immune dysregulation, as seen in the multiple severe autoimmune phenotypes of the mother, and FGR. Our experience confirms the importance of thorough workup in individuals with reduced penetrance of 22q11.2 DS features or atypical clinical presentations.

Distinct immune trajectories in patients with chromosome 22q11.2 deletion syndrome and immune-mediated diseases

BACKGROUND

Identification of biomarkers associated with immune-mediated diseases in 22q11.2 deletion syndrome is an evolving field.

OBJECTIVES

We sought to use a carefully phenotyped cohort to study immune parameters associated with autoimmunity and atopy in 22q11.2 deletion syndrome to define biomarkers associated with immune-mediated disease in this syndrome.

METHODS

Chart review validated autoimmune disease and atopic condition diagnoses. Laboratory data were extracted for each subcohort and plotted according to age. A random-effects model was used to define statistical significance.

RESULTS

CD19, CD4, and CD4/45RA lymphocyte populations were not different from the general cohort for patients with atopic conditions. CD4/45RA T cells were significantly lower in the subjects with immune thrombocytopenia compared with the general cohort, and CD4 T-cell counts were lower in patients with autoimmune thyroid disease.

CONCLUSIONS

The mechanisms of autoimmunity in cytopenias may be distinct from those of solid-organ autoimmunity in 22q11.2 deletion syndrome. This study identifies potential biomarkers for risk stratification among commonly obtained laboratory studies.

Care of Children with DiGeorge Before and After Cultured Thymus Tissue Implantation

Background

Children with complete DiGeorge anomaly (cDGA) have congenital athymia plus a myriad of other challenging clinical conditions. The term cDGA encompasses children with congenital athymia secondary to 22q11.2DS, CHARGE syndrome (coloboma, heart defects, choanal atresia, growth or mental retardation, genital abnormalities, and ear abnormalities and/or deafness), and other genetic abnormalities. Some children have no known genetic defects. Since 1993, more than 100 children with congenital athymia have been treated with cultured thymus tissue implantation (CTTI). Naïve T cells develop approximately 6 to 12 months after CTTI. Most of the children had significant comorbidities such as heart disease, hypoparathyroidism, and infections requiring complex clinical care post cultured thymus tissue implantation (CTTI).

Objective

The purpose of this guidance is to assist multidisciplinary teams in caring for children with cDGA both before and after CTTI.

Methods

Thirty-one specialists, in addition to the authors, were asked to share their experience in caring for children with cDGA at Duke University Health System, before and after CTTI. These specialists included physicians, nurses, dentists, therapists, and dieticians.

Results

The goal of a multidisciplinary approach is to have children in the best possible condition for receiving CTTI and provide optimal care post CTTI through development of naïve T cells and beyond. The CTT (cultured thymus tissue) must be protected from high doses of steroids which can damage CTT. Organs must be protected from adverse effects of immunosuppression.

Conclusion

Creating a multidisciplinary team and a detailed plan of care for children with cDGA is important for optimal outcomes.

Neutrophils to lymphocytes ratio and psychosis in 22q11.2 deletion syndrome - Clinical and scientific implications

BACKGROUND

Individuals with 22q11.2 deletion syndrome (22q11.2DS) are at risk for having both psychotic and immune disorders, thus, implying a possible link between the two. The aim of the current study was to evaluate the usefulness of the neutrophiles to leukocytes ratio (NLR), an inflammatory marker, as a bio-marker for overt and prodromal psychotic symptoms in 22q11.2DS.

METHODS

Forty-nine individuals with 22q11.2DS (13 with psychotic disorders and 36 without psychotic disorders) and 30 age- and sex-matched healthy controls underwent psychiatric evaluation using a structured psychiatric interview, the Scale of Prodromal Symptoms (SOPS) and the Global Assessment of Functioning (GAF) scale. Blood samples were collected from all participants on the day of assessment. NLR was calculated, compared among the study groups and correlated with SOPS and GAF scores. The non-psychotic 22q11.2DS group was further divided into high- and low-inflammation groups by NLR values and the analyses were done again.

RESULTS

NLR was higher in the psychotic- and the high-inflammation non-psychotic 22q11.2DS groups compared to the low-inflammation non-psychotic 22q11.2DS group and controls. In the high-inflammation non-psychotic 22q11.2DS group NLR increase was associated with an increase of total negative symptoms scores on SOPS and a decrease in GAF scores.

CONCLUSION

Our results suggest the potential utility of NLR as a bio-marker for psychotic disorders and subthreshold prodromal symptoms in 22q11.2DS. Furthermore, they imply that a disequilibrium between the innate and adaptive arms of the immune system facilitates the progression of psychosis in at risk populations. Further longitudinal studies are warranted to validate our findings, as this was a cross sectional observation.

Recurrent Evans Syndrome in a Patient With 22q11.2 Deletion Syndrome: An Uncommon Hematological Presentation

We discuss the case of a three-year-old female patient who presented with a severe episode of immune thrombocytopenia (ITP) and autoimmune hemolytic anemia (AIHA), confirming a diagnosis of Evans syndrome (ES). Over time, she continued to have several episodes of recurrent ITP until, several years later, she experienced a recurrent severe, refractory ES episode. Initially, she responded well to conventional treatment with steroids and intravenous immunoglobulin (IVIG); however, during later episodes, she required anti-CD20 therapy (rituximab). Due to peculiar facies and severe clinical presentation, an underlying immune dysregulation was suspected, which was later confirmed to be 22q11.2 deletion syndrome (22q11.2DS). Over time, her baseline immunoglobulin production decreased significantly. After monthly IVIG replacement, she had a marked reduction in ITP or AIHA events. 22q11.2DS is a frequently underdiagnosed primary immune disorder (PID). Low immunoglobulin production and recurrent ES are infrequent events associated with 22q11.2DS. This condition might cause profound immune dysregulation, predisposing patients to immune-related hematological dyscrasias that still need further research to be fully understood and characterized. We describe a case of 22q11.2DS and recurrent ES episodes, which involves a 13-year history of longitudinal follow-up care.

Relationship Between Severity of T Cell Lymphopenia and Immune Dysregulation in Patients with DiGeorge Syndrome (22q11.2 Deletions and/or Related TBX1 Mutations): a USIDNET Study

PURPOSE

DiGeorge syndrome has substantial heterogeneity with variable immune deficiency and dysregulation. Implicated immunopathology includes reduced thymic output and increased peripheral homeostatic proliferation with Th2 skewing and expansion of self-reactive cells. We hypothesized that T cell lymphopenia severity will be associated with higher odds of autoimmunity and/or asthma.

METHODS

Using the US Immunodeficiency Network registry, we identified patients with 22q11.2 deletion (and/or TBX1). Initial absolute CD3+ T cell values were stratified: normal, 50-99% and below 50% of the lower limit of age-adjusted normal values. Patients with and without reported autoimmunity and asthma were compared using chi-square tests and multivariate logistic regression.

RESULTS

Among 415 patients, autoimmunity was reported in 17 (4.1%), and asthma was reported in 28 (6.7%). Compared with those with no reported autoimmunity, patients with reported autoimmunity more frequently had low CD19+ B cells [3.3% (12/364) vs 28.6% (4/14); p = 0.002] and low IgG [6.2% (20/321) vs 29.4% (5/17); p = 0.005] levels. There were no statistically significant differences in other immune characteristics among those with and without reported asthma. Patients with absolute CD3 levels below 50% of age-adjusted normal values had higher odds of reported autoimmunity (n = 319, OR = 7.56, 95% CI = 1.58-36.17, p = 0.01) and reported asthma (n = 319, OR = 4.5, 95% CI = 1.06-18.93, p = 0.04) as compared with those with normal CD3 values, adjusted for age and low IgG.

CONCLUSIONS

Absolute CD3+ T cell counts below 50% of age-adjusted normal values may be associated with higher odds of autoimmunity and/or asthma in patients with DiGeorge syndrome and be potentially useful to identify higher-risk patients.

T-Cell Immunodeficiencies With Congenital Alterations of Thymic Development: Genes Implicated and Differential Immunological and Clinical Features

Combined Immunodeficiencies (CID) are rare congenital disorders characterized by defective T-cell development that may be associated with B- and NK-cell deficiency. They are usually due to alterations in genes expressed in hematopoietic precursors but in few cases, they are caused by impaired thymic development. Athymia was classically associated with DiGeorge Syndrome due to TBX1 gene haploinsufficiency. Other genes, implicated in thymic organogenesis include FOXN1, associated with Nude SCID syndrome, PAX1, associated with Otofaciocervical Syndrome type 2, and CHD7, one of the genes implicated in CHARGE syndrome. More recently, chromosome 2p11.2 microdeletion, causing FOXI3 haploinsufficiency, has been identified in 5 families with impaired thymus development. In this review, we will summarize the main genetic, clinical, and immunological features related to the abovementioned gene mutations. We will also focus on different therapeutic approaches to treat SCID in these patients.

Inborn Errors of Adaptive Immunity in Down Syndrome

Down syndrome fits an immunophenotype of combined immunodeficiency with immunodysregulation, manifesting with increased susceptibility to infections, autoimmunity, autoinflammatory diseases, and hematologic malignancies. Qualitative and quantitative alterations in innate and adaptive immunity are found in most individuals with Down syndrome. However, there is substantial heterogeneity and no correlation between immunophenotype and clinical presentation. Previously, it was thought that the immunological changes in Down syndrome were caused by precocious aging. We emphasize in this review that the immune system in Down syndrome is intrinsically different from the very beginning. The overexpression of specific genes located on chromosome 21 contributes to immunodeficiency and immunodysregulation, but gene expression differs between genes located on chromosome 21 and depends on tissue and cell type. In addition, trisomy 21 results in gene dysregulation of the whole genome, reflecting the complex nature of this syndrome in comparison to well-known inborn errors of immunity that result from monogenic germline mutations. In this review, we provide an updated overview focusing on inborn errors of adaptive immunity in Down syndrome.

Autoimmune Thyroid Disease in Specific Genetic Syndromes in Childhood and Adolescence

Autoimmune thyroid disease (ATD) is the most frequent cause of acquired thyroid dysfunction, most commonly presenting either as Hashimoto's thyroiditis or Graves' Disease. Hashimoto's thyroiditis is characterized by the presence of thyroid-specific autoantibodies, more commonly anti-thyroperoxidase antibodies in the serum and the typical inhomogeneous echostructure of the thyroid on a thyroid ultrasound examination. Hashimoto's thyroiditis can for a long time be accompanied by normal thyroid function and hypothyroidism can only progressively be established. Graves' disease is much less frequent in childhood and adolescence and presents with overt hyperthyroidism. After the onset of puberty, ATD affects females with a higher incidence than males, while during the prepubertal period there is not such a clear preponderance of affected females. ATD can occur either isolated or in the context of other autoimmune disorders, such as type 1 Diabetes mellitus (T1D), celiac disease, alopecia areata, vitiligo, etc. Especially at the pediatric age, a higher incidence of ATD is also observed in the context of specific genetic syndromes, such as trisomy 21 (Down syndrome), Klinefelter syndrome, Turner syndrome, or 22q11.2 deletion syndrome. Nevertheless, although thyroid dysfunction may also be observed in other genetic syndromes, such as Prader-Willi or Williams syndrome, the thyroid dysfunction in these syndromes is not the result of thyroid autoimmunity. Interestingly, there is emerging evidence supporting a possible link between autoimmunity and RASopathies. In this review article the incidence, as well as the clinical manifestation and accompanied pathologies of ATD in specific genetic syndromes will be presented and regular follow-up for the early identification of the disorder will be proposed.

Chromosome 22q11.2 deletion syndrome and DiGeorge syndrome

Chromosome 22q11.2 deletion syndrome is the most common microdeletion syndrome in humans. The effects are protean and highly variable, making a unified approach difficult. Nevertheless, commonalities have been identified and white papers with recommended evaluations and anticipatory guidance have been published. This review will cover the immune system in detail and discuss both the primary features and the secondary features related to thymic hypoplasia. A brief discussion of the other organ system involvement will be provided for context. The immune system, percolating throughout the body can impact the function of other organs through allergy or autoimmune disease affecting organs in deleterious manners. Our work has shown that the primary effect of thymic hypoplasia is to restrict T cell production. Subsequent homeostatic proliferation and perhaps other factors drive a Th2 polarization, most obvious in adulthood. This contributes to atopic risk in this population. Thymic hypoplasia also contributes to low regulatory T cells and this may be part of the overall increased risk of autoimmunity. Collectively, the effects are complex and often age-dependent. Future goals of improving thymic function or augmenting thymic volume may offer a direct intervention to ameliorate infections, atopy, and autoimmunity.

Immune system defects in DiGeorge syndrome and association with clinical course

We evaluated 18 DiGeorge syndrome (DGS) patients and aimed to investigate the immunological changes in this population. DGS patients with low naive CD4⁺ T and CD8⁺ T cells were defined as high-risk (HR) patients, whereas patients with normal numbers of naive CD4⁺ and CD8⁺ T cells were defined as standard risk (SR) patients. Level of serum IgM, CD3⁺ T cell counts and percentages of class-switched memory B cells were significantly low in HR group compared to SR ones. Severe infections and persistent hypoparathyroidism were detected significantly higher in HR group. Patients with reduced percentages of class-switched B cells had earlier onset of infection, lower blood IgM, lower CD4⁺ and CD8⁺ T counts than patients with normal class-switched memory B cells. Decreased levels of IgM were associated with low numbers of naive CD4⁺ and recent thymic emigrants T cells. Monitoring the immune changes of patients with DGS would be useful to predict the severe phenotype of disease.

Risk factors of clinical dysimmune manifestations in a cohort of 86 children with 22q11.2 deletion syndrome: A retrospective study in France

In this study, we describe the biological immune profiles and clinical dysimmune manifestations (infections, autoimmune diseases, and allergies) of patients with 22q11.2 deletion syndrome with the aim of determining risk factors for clinical events. This retrospective study concerned all the patients with 22q11 deletion syndrome attending the Montpellier University Hospital from January 1, 1992, to December 31, 2014 who had at least one immune investigation before the age of 18. We analyzed the clinical features, biological tests and the course of infections, autoimmunity, and allergy of 86 children. Among these 86 children, 48 (59%) had a low T lymphocyte level. Twenty-nine patients (34%) had a severe infection. The only risk factor for severe infection was the low level of CD4+ T-cells (OR: 3.3; 95% confidence interval (CI) [1.020-11.108]). Eleven patients (13%) developed an autoimmune disease; the only risk factor was an antecedent of severe infection (OR: 4.1; 95% CI [1.099-15.573]). Twenty-three patients (27%) had allergic episodes. A low level of CD8+ T-cells (OR: 3.2; 95% CI [1.07-9.409]) was significantly associated with allergy manifestations. Patients with 22q11 deletion syndrome have a high rate of dysimmune manifestations. We found statistic correlations among CD4+ T-cell count, infectious manifestations, and autoimmunity.

Clinical and immunological features in a cohort of patients with partial DiGeorge syndrome followed at a single center

DiGeorge syndrome (DGS) is a primary immunodeficiency characterized by various degrees of T-cell deficiency. In partial DGS (pDGS), other risk factors could predispose to recurrent infections, autoimmunity, and allergy. The aim of this study was to assess the effect of different factors in the development of infections, autoimmunity, and/or allergy in patients with pDGS. We studied 467 pDGS patients in follow-up at Great Ormond Street Hospital. Using a multivariate approach, we observed that palatal anomalies represent a risk factor for the development of recurrent otitis media with effusion. Gastroesophageal reflux/dysphagia and asthma/rhinitis represent a risk factor for the development of recurrent upper respiratory tract infections. Allergy and autoimmunity were associated with persistently low immunoglobulin M levels and lymphopenia, respectively. Patients with autoimmunity showed lower levels of CD3⁺, CD3⁺CD4⁺, and naïve CD4⁺CD45RA⁺CD27⁺ T lymphocytes compared with pDGS patients without autoimmunity. We also observed that the physiological age-related decline of the T-cell number was slower in pDGS patients compared with age-matched controls. The age-related recovery of the T-cell number depended on a homeostatic peripheral proliferation of T cells, as suggested by an accelerated decline of the naïve T lymphocytes in pDGS as well as a more skewed T-cell repertoire in older pDGS patients. These evidences suggest that premature CD4⁺ T-cell aging and lymphopenia induced spontaneous peripheral T-cell proliferation might contribute to the pathogenesis of autoimmunity in patients with pDGS. Infections in these patients represent, in most of the cases, a complication of anatomical or gastroenterological anomalies rather than a feature of the underlying immunodeficiency.

Characteristics and Outcomes of Heart Transplantation in DiGeorge Syndrome

DiGeorge syndrome (DGS) is commonly associated with both congenital heart disease (CHD) and immunologic abnormalities. While CHD may prompt consideration for heart transplantation (HTx), little is known about HTx management or outcomes in this group. The aim of this study was to describe the spectrum of patients with DGS who undergo HTx and report post-HTx outcomes. All pediatric HTx recipients (2002-2016) with DGS were identified using ICD codes from a linked billing and clinical registry database. Patient characteristics and outcomes were described and compared to non-DGS HTx recipients with CHD. Kaplan-Meier methods were used to assess overall survival, freedom from infection, and freedom from rejection. A total of 17 patients with DGS who underwent HTx at 12 different centers were included. Median age at HTx was 5 years (IQR 0-13 years). Steroids were used for induction in all patients in addition to thymoglobulin in 13/17 (76%) and IL2R antagonists in 3/17 (18%). Maintenance immunosuppression was a combination of tacrolimus or cyclosporine and mycophenolate or azathioprine in 16/17 (94%). Half received steroids at the time of discharge. There were six deaths (35%). The median post-HTx survival was 5.4 years with no difference in freedom from rejection, infection, or overall survival between patients with and without DGS. Patients with DGS undergoing HTx received standard immunosuppression. We found no difference in freedom from infection, rejection, or overall post-HTx survival compared to non-DGS patients, although the small size of our study resulted in limited statistical power. Given the potential for favorable outcomes, patients with DGS may be considered for HTx in the appropriate clinical setting.

Immunophenotype Anomalies Predict the Development of Autoimmune Cytopenia in 22q11.2 Deletion Syndrome

BACKGROUND

Patients with 22q11.2 deletion syndrome (22q11.2DS) may develop severe thrombocytopenic purpura and hemolytic anemia. There are no reliable predictors for the development of hematologic autoimmunity (HA) in these patients.

OBJECTIVE

To describe the peculiar B and T subpopulation defects in patients with 22q11DS who have developed HA and test if these defects precede the development of HA.

METHODS

We performed a case-control multicenter study. Patients with HA were compared with a control population of 22q11.2DS without HA (non-HA). A complete immunological evaluation was performed at diagnosis and at the last follow-up including extensive T and B phenotypes.

RESULTS

Immunophenotype at the last follow-up was available in 23 HA and 45 non-HA patients. HA patients had significantly decreased percentage of naïve CD4⁺ cells (26.8% vs 43.2%, P = .003) and recent thymic emigrants (48.6% vs 80.5%, P = .046); decreased class-switched B cells (2.0% vs 5.9%, P = .04) and increased naive B cells (83.5% vs 71.4%, P = .02); increased CD16+/56+ both in absolute number (312 vs 199, P = .009) and percentage (20.0% vs 13.0%, P = .03). Immunophenotype was performed in 36 patients (11 HA and 25 non-HA) at diagnosis. Odds ratio (OR) of immune cytopenia were estimated for both CD4 naïve ≤30% (OR 14.0, P = .002) and switched memory B cells ≤2% (OR 44.0, P = .01). The estimated survival curves reached statistical significance, respectively, P = .0001 and P = .002.

CONCLUSIONS

Among patients with 22q11.2DS, those with HA have characteristic lymphocyte anomalies that appear considerably before HA onset. Systematic immunophenotyping of patients with 22q11.2DS at diagnosis is advisable for early identification of patients at risk for this severe complication.

Clinical and immunophenotypic characteristics of patients with chromosome 22q11.2 deletion syndrome: a single institution's experience

Aim

The aim of this study was to identify the clinical and immunologic features of patients with 22q11.2 deletion syndrome who were followed up in our clinic. Thus, it is aimed to identify the syndrome early, choose the right treatment options according to humoral and cellular immunologic analysis, and enlighten how to follow up these kinds of patients with immunodeficiencies.

Material and Methods

We retrospectively collected data by reviewing the files of 11 patients with 22q11.2 deletion syndrome who were followed up in our clinic between January 2003 and January 2015. The diagnoses were based on the patients' clinical, genetic, and immunologic features. Demographic features, family history, initial symptoms on admission, physical findings, and results of immunologic studies of the patients. Age of diagnosis, treatment options, and clinical follow-up were evaluated.

Results

The patients' diagnosis age ranged from 1-11 months and the most common symptoms of admission were cardiac murmur and atypical facial appearance, which were detected during a routine physical examination. All patients had cardiac anomalies, and four patients had a history of cardiovascular surgery. Eight patients (72.7%) had a history of severe infection; recurrent lower respiratory tract infections were reported in six patients (54.5%), pulmonary tuberculosis in one patient (9.1%), and moniliasis resistant to treatment was detected in one patient. None of the patients required intravenous immunoglobulin replacement therapy, and antibiotic prophylaxis was administered to two patients with lymphopenia.

Conclusion

22q11.2 deletion syndrome is a multi-systemic disorder that should be evaluated by a multidisciplinary team. It should be kept in mind for patients with neonatal hypocalcemic tetany or recurrent infections or atypical facial appearance with cardiac anomalies. Early diagnosis should lead to immunologic analysis and enable the choice of treatment. Preventive measures against infection is recommended for the patients with incomplete immunodeficiency, and thymus transplantation is recommended for patients with complete immunodeficiency.

Primary immunodeficiency and autoimmunity: A comprehensive review

The primary immunodeficiency diseases (PIDs) include many genetic disorders that affect different components of the innate and adaptive responses. The number of distinct genetic PIDs has increased exponentially with improved methods of detection and advanced laboratory methodology. Patients with PIDs have an increased susceptibility to infectious diseases and non-infectious complications including allergies, malignancies and autoimmune diseases (ADs), the latter being the first manifestation of PIDs in several cases. There are two types of PIDS. Monogenic immunodeficiencies due to mutations in genes involved in immunological tolerance that increase the predisposition to develop autoimmunity including polyautoimmunity, and polygenic immunodeficiencies characterized by a heterogeneous clinical presentation that can be explained by a complex pathophysiology and which may have a multifactorial etiology. The high prevalence of ADs in PIDs demonstrates the intricate relationships between the mechanisms of these two conditions. Defects in central and peripheral tolerance, including mutations in AIRE and T regulatory cells respectively, are thought to be crucial in the development of ADs in these patients. In fact, pathology that leads to PID often also impacts the Treg/Th17 balance that may ease the appearance of a proinflammatory environment, increasing the odds for the development of autoimmunity. Furthermore, the influence of chronic and recurrent infections through molecular mimicry, bystander activation and super antigens activation are supposed to be pivotal for the development of autoimmunity. These multiple mechanisms are associated with diverse clinical subphenotypes that hinders an accurate diagnosis in clinical settings, and in some cases, may delay the selection of suitable pharmacological therapies. Herein, a comprehensively appraisal of the common mechanisms among these conditions, together with clinical pearls for treatment and diagnosis is presented.

Downregulation of genes outside the deleted region in individuals with 22q11.2 deletion syndrome

The 22q11.2 deletion syndrome (22q11.2DS) is caused by recurrent hemizygous deletions of chromosome 22q11.2. The phenotype of the syndrome is complex and varies widely among individuals. Little is known about the role of the different genes located in 22q11.2, and we hypothesized that genetic risk factors lying elsewhere in the genome might contribute to the phenotype. Here, we present the whole-genome gene expression data of 11 patients with approximately 3 Mb deletions. Apart from the hemizygous genes mapped to the 22q11.2 region, the TUBA8 and GNAZ genes, neighboring the deleted interval but in normal copy number, showed altered expression. When genes mapped to other chromosomes were considered in the gene expression analysis, a genome-wide dysregulation was observed, with increased or decreased expression levels. The enriched pathways of these genes were related to immune response, a deficiency that is frequently observed in 22q11.2DS patients. We also used the hypothesis-free weighted gene co-expression network analysis (WGCNA), which revealed the co-expression gene network modules with clear connection to mechanisms associated with 22q11.2DS such as immune response and schizophrenia. These findings, combined with the traditional gene expression profile, can be used for the identification of potential pathways and genes not previously considered to be related to the 22q11.2 deletion syndrome.

Lymphocyte Apoptosis and FAS Expression in Patients with 22q11.2 Deletion Syndrome

PURPOSE

Immunodeficiency is one of the key features of 22q11.2 deletion syndrome (del), and it is seen in approximately 75% of the patients. The degree of immunodeficiency varies widely, from no circulating T cells to normal T cell counts. It has been hypothesized that the low number of T cells may at least in part be due to increased apoptosis of T cells. Increased spontaneous T cell apoptosis has been reported in one patient with 22q11.2del, but this has not been further investigated.

METHODS

A national cohort of patients with a proven heterozygous deletion of chromosome 22q11.2 diagnosed by FISH or MLPA and a group of age and sex matched controls were studied. Spontaneous and activation-induced apoptosis, in addition to FAS expression on lymphocytes, were measured using flow cytometry. Serum levels of FASL were analyzed using ELISA.

RESULTS

There was no increased spontaneous apoptosis in patients with 22q11.2del. Upon activation, anti-FAS-induced apoptosis was significantly increased in patients compared to those in controls, while there was no difference in activation induced cell death or activated cell autonomous death. We also found a significant increase in expression of FAS on freshly isolated lymphocytes from patients, while there was no difference in serum levels of FASL. Patients with congenital heart defects (CHD) had significantly higher serum levels of FASL compared to non-CHD patients.

CONCLUSION

We have shown increased FAS expression on lymphocytes from patients with 22q11.2del as well as increased levels of FASL in patients with CHD. Those changes may contribute to the pathophysiology of the 22q11.2del.

Fatal overwhelming postsplenectomy infection due to Streptococcus pneumoniae serotype 10A with atypical polysaccharide capsule in a patient with chromosome 22q11.2 deletion syndrome: A case report

We report the first case of a teenage patient with chromosome 22q11.2 deletion syndrome who died of overwhelming postsplenectomy infection (OPSI) by Streptococcus pneumoniae despite appropriate prevention by pneumococcal vaccine. He had congenital heart disease and underwent several surgeries. Immunodeficiency had not been noticed clinically. Two years prior to death, splenectomy was performed for a drug-resistant idiopathic thrombocytopenic purpura and he was immunized with 23-valent pneumococcal polysaccharide vaccine (PPV23) 4 months after splenectomy. He died suddenly after a mild flu-like symptom. Autopsy was performed and OPSI was diagnosed. Blood culture was positive for S. pneumoniae. This isolated S. pneumoniae strain was serotypically un-typable by polyvalent serum agglutination test. On the contrary, multilocus sequence typing followed by DNA sequencing indicated the molecular serotype as 10A. Additional testing using monovalent and factor-specific sera confirmed the strain as serotype 10A. Ultrastructural observation of this S. pneumoniae strain showed that the polysaccharide capsule was thin and sparse. We speculate that the abnormal morphology of the capsule may have accounted for the polyvalent serum agglutination failure and may possibly be associated with severity of OPSI observed in this case. Chromosome 22q11.2 deletion syndrome is associated with certain immunodeficiency, especially susceptible to S. pneumoniae infections; however, fatal OPSI has not been reported. In addition to vaccination, prophylactic antibiotics may be necessary for these patients who are at risk of immunodeficiency.

Follicular Helper T Cells in DiGeorge Syndrome

DiGeorge syndrome is an immunodeficiency characterized by thymic dysplasia resulting in T cell lymphopenia. Most patients suffer from increased susceptibility to infections and heightened prevalence of autoimmune disorders, such as autoimmune thrombocytopenia. B cells in DiGeorge syndrome show impaired maturation, with low switched-memory B cells and a wide spectrum of antibody deficiencies or dysgammaglobulinemia, presumably due to impaired germinal center responses. We set out to evaluate circulating follicular helper T cells (cTFHs) in DiGeorge syndrome, as markers of T–B interaction in the germinal centers in a cohort of 17 patients with partial DiGeorge and 21 healthy controls of similar age. cTFHs were characterized as CXCR5⁺CD45RA⁻ CD4⁺ T cells using flow cytometry. We verify previous findings that the population of memory CD4⁺ T cells is relatively increased in diGeorge patients, corresponding to low naïve T cells and impaired T cell production in the thymus. The population of CXCR5⁺ memory CD4⁺ T cells (cTFHs) was significantly expanded in patients with DiGeorge syndrome, but only healthy controls and not DiGeorge syndrome patients showed gradual increase of CXCR5 expression on cTFHs with age. We did not observe correlation between cTFHs and serum IgG levels or population of switched memory B cells. There was no difference in cTFH numbers between DiGeorge patients with/without thrombocytopenia and with/without allergy. Interestingly, we show strong decline of PD1 expression on cTFHs in the first 5 years of life in DiGeorge patients and healthy controls, and gradual increase of PD1 and ICOS expression on CD4⁻ T cells in healthy controls later in life. Thus, here, we show that patients with DiGeorge syndrome have elevated numbers of cTFHs, which, however, do not correlate with autoimmunity, allergy, or production of immunoglobulins. This relative expansion of cTFH cells may be a result of impaired T cell development in patients with thymic dysplasia.

A pilot study on immuno-psychiatry in the 22q11.2 deletion syndrome: A role for Th17 cells in psychosis?

BACKGROUND

A growing body of evidence supports a role for immune alterations in Schizophrenia Spectrum Disorders (SSD). A high prevalence (25-40%) of SSD has been found in patients with 22q11.2 deletion syndrome (22q11.2DS), which is known for T-cell deficits due to thymus hypoplasia. This study is the first to explore the association between the T-cell subsets and psychotic symptoms in adults with 22q11.2DS.

METHODS

34 individuals (aged 19-38 yrs.) with 22q11.2DS and 34 healthy age- and gender matched control individuals were included. FACS analysis of the blood samples was performed to define T-cell subsets. Ultra-high risk for psychosis or diagnosis of SSD was determined based on CAARMS interviews and DSM-5 criteria for SSD. Positive psychotic symptom severity was measured based on the PANSS positive symptoms subscale.

RESULTS

A partial T-cell immune deficiency in 22q11.2DS patients was confirmed by significantly reduced percentages of circulating T and T-helper cells. Significantly higher percentages of inflammatory Th1, Th17, and memory T-helper cells were found in adults with 22q11.2DS. Most importantly an increased Th17 percentage was found in adults with psychotic symptoms as compared to non-psychotic adults with 22q11.2DS, and Th17 percentage were related to the presence of positive psychotic symptoms.

CONCLUSIONS

Given the literature on the role of T cells and in particular of Th17 cells and IL-17 in hippocampus development, cognition and behavior, these results support the hypothesis for a role of Th17 cells in the development and/or regulation of psychotic symptoms in 22q11.2DS. This pilot study underlines the importance to further study the role of T-cell defects and of Th17 cells in the development of psychiatric symptoms. It also supports the possibility to use 22q11.2DS as a model to study T-cell involvement in the development of SSD.

Variable immune deficiency related to deletion size in chromosome 22q11.2 deletion syndrome

The clinical features of 22q11.2 deletion syndrome include virtually every organ of the body. This review will focus on the immune system and the differences related to deletion breakpoints. A hypoplastic thymus was one of the first features described in this syndrome and low T cell counts, as a consequence of thymic hypoplasia, are the most commonly described immunologic feature. These are most prominently seen in early childhood and can be associated with increased persistence of viruses. Later in life, evidence of T cell exhaustion may be seen and secondary deficiencies of antibody function have been described. The relationship of the immunodeficiency to the deletion breakpoints has been understudied due to the infrequent analysis of people carrying smaller deletions. This manuscript will review the immune deficiency in 22q11.2 deletion syndrome and describe differences in the T cell counts related to the deletion breakpoints. Distal, non-TBX1 inclusive deletions, were found to be associated with better T cell counts. Another new finding is the relative preservation of T cell counts in those patients with a 22q11.2 duplication.

The Impact of 22q11.2 Microdeletion on Cardiac Surgery Postoperative Outcome

22q11.2 microdeletion is the most common microdeletion in humans. The purpose of this study was to evaluate postoperative outcome in children with 22q11.2 microdeletion who had undergone complete surgical correction of a congenital heart defect. The study included 34 patients who underwent complete correction of conotruncal heart defects. Of these, 17 patients diagnosed with 22q11.2 microdeletion represent the investigated group. Another 17 patients without 22q11.2 microdeletion represent the control group. Investigated and control groups differ significantly for total length of stay in the hospital (average 37.35 and 14.12 days, respectively); length of postoperative stay in the intensive care unit (average 10.82 and 6.76 days, respectively); sepsis (eight and two patients, respectively); administration of antibiotics (15 and seven patients, respectively); duration of antibiotic therapy (average 17.65 and 14.59 days, respectively); occurrence of hypocalcemia (16 and 0 patients, respectively); and initiation of peroral nutrition during the postoperative course (average 10.29 and 3.88 days, respectively). No difference was found for duration of ventilatory support (average 6.12 and 4.24 days, respectively), administration of total parenteral nutrition, and postoperative mortality rate. The study results suggest that genotype of 22q11.2 microdeletion affects postoperative outcome after cardiac surgery. Possible targets for intervention in postoperative intensive care management are prevention and treatment of systemic infections, monitoring, and treatment of hypocalcemias, rational administration of antibiotics and careful planning of nutrition. Consequently, this could shorten patients' intensive care stay and overall duration of hospitalization.

Immunodeficiency in CHARGE syndrome

Immunodeficiency can occur in CHARGE syndrome, with immunophenotypes including reduction in T-cell counts, combined T-B cell defects rarely requiring antibiotic prophylaxis or immunoglobulin replacement, and severe combined immunodeficiency, which is fatal without immune reconstitution. However, the prevalence of immunodeficiency in CHARGE syndrome remains unclear with few prospective studies. In this review, we examine the existing literature covering immunodeficiency associated with CHARGE syndrome, compare these with immunodeficiencies reported in 22q11.2 deletion syndrome (a condition that shares many phenotypic characteristics with CHARGE syndrome) and suggest future research priorities.

Mechanism-Based Strategies for the Management of Autoimmunity and Immune Dysregulation in Primary Immunodeficiencies

A broad spectrum of autoimmunity is now well described in patients with primary immunodeficiencies (PIDs). Management of autoimmune disease in the background of PID is particularly challenging given the seemingly discordant goals of immune support and immune suppression. Our growing ability to define the molecular underpinnings of immune dysregulation has facilitated novel targeted therapeutics. This review focuses on mechanism-based treatment strategies for the most common autoimmune and inflammatory complications of PID including autoimmune cytopenias, rheumatologic disease, and gastrointestinal disease. We aim to provide guidance regarding the rational use of these agents in the complex PID patient population.

The 22q11.2 deletion syndrome: Cancer predisposition, platelet abnormalities and cytopenias

The 22q11.2 deletion syndrome (DS) is associated with variable phenotypic expression as findings range from severely affected individuals with the classical triad of DiGeorge and velocardiofacial syndromes, including congenital heart disease, immunodeficiency, hypocalcemia, and palatal abnormalities, to subtly affected adults who only come to attention following the diagnosis of a more severely affected child. The multiple manifestations can affect all organ systems, including the hematologic system resulting in baseline lower platelet counts for individuals with 22q11.2DS and increased platelet size. In addition, there may be an associated increased risk of bleeding. Individuals with 22q11.2DS are also at increased risk of autoimmune cytopenias that can complicate the evaluation or management of other manifestations. Finally, there may be an increased risk of malignancy, although the mechanism for this risk is not fully understood. This review summarizes the currently available data on hematologic/oncologic manifestations of 22q11.2DS and reports on our findings within a large cohort of individuals with the deletion.