DiGeorge anomaly: a comparative study of the clinical and immunologic characteristics of patients positive and negative by fluorescence in situ hybridization

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.

Prevalence of hearing loss and clinical otologic manifestations in patients with 22q11.2 deletion syndrome: A literature review

BACKGROUND

Hearing loss and otitis media are frequently reported in patients with 22q11.2 deletion syndrome.

OBJECTIVE OF REVIEW

Our objective was to review the current literature on the prevalence of hearing loss and otologic manifestations in patients with 22q11.2 deletion syndrome.

TYPE OF REVIEW

Systematic review.

SEARCH STRATEGY

We conducted a systematic search in PubMed and Embase combining the term "22q11.2 deletion syndrome" and synonyms with "hearing loss" and "otologic manifestations" and synonyms.

EVALUATION METHOD

We screened title/abstract and full text of all retrieved articles on pre-defined in- and exclusion criteria. The remaining articles were assessed on risk of bias. Outcome measures included the prevalence of hearing loss and otologic manifestations such as otitis media.

RESULTS

Our search yielded 558 unique studies of which a total of 25 articles were included for critical appraisal and data extraction. Twenty-one studies reported on hearing loss, and 21 studies on otologic manifestations. The prevalence of hearing loss varied from 6.0% to 60.3%, where in most studies conductive hearing loss was most prevalent. Rates of recurrent or chronic otitis media varied from 2.2% to 89.8%.

CONCLUSION

Although a very broad range in prevalences is reported in different studies, hearing loss and recurrent or chronic otitis media are frequently present in patients with 22q11.2 deletion syndrome. Regular check-ups and audiometric testing are advised in these patients.

Integrative transcriptome network analysis of iPSC-derived neurons from schizophrenia and schizoaffective disorder patients with 22q11.2 deletion

BACKGROUND

Individuals with 22q11.2 Deletion Syndrome (22q11.2 DS) are a specific high-risk group for developing schizophrenia (SZ), schizoaffective disorder (SAD) and autism spectrum disorders (ASD). Several genes in the deleted region have been implicated in the development of SZ, e.g., PRODH and DGCR8. However, the mechanistic connection between these genes and the neuropsychiatric phenotype remains unclear. To elucidate the molecular consequences of 22q11.2 deletion in early neural development, we carried out RNA-seq analysis to investigate gene expression in early differentiating human neurons derived from induced pluripotent stem cells (iPSCs) of 22q11.2 DS SZ and SAD patients.

METHODS

Eight cases (ten iPSC-neuron samples in total including duplicate clones) and seven controls (nine in total including duplicate clones) were subjected to RNA sequencing. Using a systems level analysis, differentially expressed genes/gene-modules and pathway of interests were identified. Lastly, we related our findings from in vitro neuronal cultures to brain development by mapping differentially expressed genes to BrainSpan transcriptomes.

RESULTS

We observed ~2-fold reduction in expression of almost all genes in the 22q11.2 region in SZ (37 genes reached p-value < 0.05, 36 of which reached a false discovery rate < 0.05). Outside of the deleted region, 745 genes showed significant differences in expression between SZ and control neurons (p < 0.05). Function enrichment and network analysis of the differentially expressed genes uncovered converging evidence on abnormal expression in key functional pathways, such as apoptosis, cell cycle and survival, and MAPK signaling in the SZ and SAD samples. By leveraging transcriptome profiles of normal human brain tissues across human development into adulthood, we showed that the differentially expressed genes converge on a sub-network mediated by CDC45 and the cell cycle, which would be disrupted by the 22q11.2 deletion during embryonic brain development, and another sub-network modulated by PRODH, which could contribute to disruption of brain function during adolescence.

CONCLUSIONS

This study has provided evidence for disruption of potential molecular events in SZ patient with 22q11.2 deletion and related our findings from in vitro neuronal cultures to functional perturbations that can occur during brain development in SZ.

The diverse clinical features of chromosome 22q11.2 deletion syndrome (DiGeorge syndrome)

A 2-year-old boy with chromosome 22q11.2 deletion syndrome was referred for recurrent sinopulmonary infections. He was diagnosed shortly after birth by a fluorescence in situ hybridization test that was performed due to interrupted aortic arch type B. He had no hypocalcemia, and his recovery from cardiac repair was uneventful. He had difficulty feeding and gained weight slowly, but, otherwise, there were no concerns during his first year of life. At 15 months of age, he began to develop significant otitis media and bronchitis. He was hospitalized once for pneumonia at 18 months of age and has never been off antibiotics for more than 1 week since then. He has not had any previous immunologic evaluation. Recurrent sinopulmonary infections in a child with chromosome 22q11.2 deletion syndrome can have the same etiologies as in any other child. Atopy, anatomic issues, cystic fibrosis, and new environmental exposures could be considered in this setting. Early childhood can be problematic for patients with chromosome 22q11.2 deletion syndrome due to unfavorable drainage of the middle ear and sinuses. Atopy occurs at a higher frequency in 22q11.2 deletion syndrome, and these children also have a higher rate of gastroesophageal reflux and aspiration than the general population. As would be appropriate for any child who presents with recurrent infections at 2 years of age, an immunologic evaluation should be performed. In this review, we will highlight recent findings and new data on the management of children and adults with chromosome 22q11.2 deletion syndrome.

Goldenhar syndrome: a cause of secondary immunodeficiency?

Goldenhar syndrome (GS) results from an aberrant development of the 1st and 2nd branchial arches. There is a wide range of clinical manifestations, the most common being microtia, hemifacial microsomia, epibulbar dermoids and vertebral malformations. We present two cases of GS and secondary immunodeficiency due to anatomical defects characteristic of this disorder. Case 1 (3-year-old female) averaged 6 episodes of sinusitis and otitis media per year. Case 2 (7-year-old female) also had recurrent otitis media, an episode of bacterial pneumonia, and 2 episodes of bacterial meningitis. Their immune evaluation included a complete blood count with differential, serum immunoglobulin levels and specific antibody concentrations, lymphocyte phenotyping, and mitogen and antigen responses, the results of which were all within normal ranges. Both children demonstrated major structural abnormalities of the inner and middle ear structures, retention of fluid in mastoid air cells, and chronic sinusitis by computed tomography. These two cases illustrate how a genetically-associated deviation of the middle ear cleft can cause recurrent infections and chronic inflammation of the middle ear and adjacent sinuses, even meninges, leading to a greatly reduced quality of life for the child and parents.

Functional gene-expression analysis shows involvement of schizophrenia-relevant pathways in patients with 22q11 deletion syndrome

22q11 Deletion Syndrome (22q11DS) is associated with dysmorphology and a high prevalence of schizophrenia-like symptoms. Several genes located on chromosome 22q11 have been linked to schizophrenia. The deletion is thought to disrupt the expression of multiple genes involved in maturation and development of neurons and neuronal circuits, and neurotransmission. We investigated whole-genome gene expression of Peripheral Blood Mononuclear Cells (PBMC's) of 8 22q11DS patients and 8 age- and gender-matched controls, to (1) investigate the expression levels of 22q11 genes and (2) to investigate whether 22q11 genes participate in functional genetic networks relevant to schizophrenia. Functional relationships between genes differentially expressed in patients (as identified by Locally Adaptive Statistical procedure (LAP) or satisfying p<0.05 and fold-change >1.5) were investigated with the Ingenuity Pathways Analysis (IPA). 14 samples (7 patients, 7 controls) passed quality controls. LAP identified 29 deregulated genes. Pathway analysis showed 262 transcripts differentially expressed between patients and controls. Functional pathways most disturbed were cell death, cell morphology, cellular assembly and organization, and cell-to-cell signaling. In addition, 10 canonical pathways were identified, among which the signal pathways for Natural Killer-cells, neurotrophin/Trk, neuregulin, axonal guidance, and Huntington's disease. Our findings support the use of 22q11DS as a research model for schizophrenia. We identified decreased expression of several genes (among which COMT, Ufd1L, PCQAP, and GNB1L) previously linked to schizophrenia as well as involvement of signaling pathways relevant to schizophrenia, of which Neurotrophin/Trk and neuregulin signaling seems to be especially notable.

Chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

Chromosome 22q11.2 deletion syndrome is a common syndrome also known as DiGeorge syndrome and velocardiofacial syndrome. It occurs in approximately 1:4000 births, and the incidence is increasing due to affected parents bearing their own affected children. The manifestations of this syndrome cross all medical specialties, and care of the children and adults can be complex. Many patients have a mild to moderate immune deficiency, and the majority of patients have a cardiac anomaly. Additional features include renal anomalies, eye anomalies, hypoparathyroidism, skeletal defects, and developmental delay. Each child's needs must be tailored to his or her specific medical problems, and as the child transitions to adulthood, additional issues will arise. A holistic approach, addressing medical and behavioral needs, can be very helpful.

Persistent low thymic activity and non-cardiac mortality in children with chromosome 22q11.2 microdeletion and partial DiGeorge syndrome

A subgroup of patients with 22q11.2 microdeletion and partial DiGeorge syndrome (pDGS) appears to be susceptible to non-cardiac mortality (NCM) despite sufficient overall CD4(+) T cells. To detect these patients, 20 newborns with 22q11.2 microdeletion and congenital heart disease were followed prospectively for 6 years. Besides detailed clinical assessment, longitudinal monitoring of naive CD4(+) and cytotoxic CD3(+)CD8(+) T cells (CTL) was performed. To monitor thymic activity, we analysed naive platelet endothelial cell adhesion molecule-1 (CD31(+)) expressing CD45RA(+)RO(-)CD4(+) cells containing high numbers of T cell receptor excision circle (T(REC))-bearing lymphocytes and compared them with normal values of healthy children (n = 75). Comparing two age periods, low overall CD4(+) and naive CD4(+) T cell numbers were observed in 65%/75%, respectively, of patients in period A (< 1 year) declining to 22%/50%, respectively, of patients in period B (> 1/< 7 years). The percentage of patients with low CTLs (< P10) remained robust until school age (period A: 60%; period B: 50%). Low numbers of CTLs were associated with abnormally low naive CD45RA(+)RO(-)CD4(+) T cells. A high-risk (HR) group (n = 11) and a standard-risk (SR) (n = 9) group were identified. HR patients were characterized by low numbers of both naive CD4(+) and CTLs and were prone to lethal infectious and lymphoproliferative complications (NCM: four of 11; cardiac mortality: one of 11) while SR patients were not (NCM: none of nine; cardiac mortality: two of nine). Naive CD31(+)CD45RA(+)RO(-)CD4(+), naive CD45RA(+)RO(-)CD4(+) T cells as well as T(RECs)/10(6) mononuclear cells were abnormally low in HR and normal in SR patients. Longitudinal monitoring of naive CD4(+) and cytotoxic T cells may help to discriminate pDGS patients at increased risk for NCM.

Velocardiofacial syndrome, DiGeorge syndrome: the chromosome 22q11.2 deletion syndromes

Velocardiofacial syndrome, DiGeorge syndrome, and some other clinical syndromes have in common a high frequency of hemizygous deletions of chromosome 22q11.2. This deletion syndrome is very common, affecting nearly one in 3000 children. Here, we focus on recent advances in cardiac assessment, speech, immunology, and pathophysiology of velocardiofacial syndrome. The complex medical care of patients needs a multidisciplinary approach, and every patient has his own unique clinical features that need a tailored approach. Patients with chromosome 22q11.2 deletion syndrome might have high level of functioning, but most often need interventions to improve the function of many organ systems.

Selective IgM deficiency and 22q11.2 deletion syndrome

BACKGROUND

The 22q11.2 deletion syndrome is a common chromosomal disorder with highly variable phenotypic expression and immunologic defects. Humoral immunity is mostly unaffected, but selective IgA deficiency occurs in up to 13% of patients. Selective IgM deficiency associated with 22q11.2 deletion has been reported in 1 patient.

OBJECTIVE

To describe another 2 patients with 22q11.2 deletion syndrome and IgM deficiency.

METHODS

Patient 1 was a 6-year-old boy with recurrent otitis media, sinopulmonary infections, wheezing, and speech delay. His serum IgM level was 18 mg/dL, and his IgA and IgG levels were normal. Antibody titers to protein and carbohydrate antigens were protective. Workup for velopharyngeal insufficiency resulted in the diagnosis of 22q11.2 deletion syndrome 3 years later. Patient 2 was a 14-year-old girl diagnosed as having 22q11.2 deletion at 9 years of age after presenting with neonatal seizures, atrial and ventricular septal defects, recurrent otitis media, mental retardation, and asthma. Her serum IgM level was 11 mg/dL, with normal IgG and IgA levels. Antibody titers to protein and carbohydrate antigens were protective. Patient 3 was a previously described 15-year-old girl with persistently draining ears, 22q11.2 deletion, and an IgM level less than 6 mg/dL. Her clinical and laboratory features are summarized.

RESULTS

Results of further testing on the patients, including lymphocyte enumeration, were normal. The literature is reviewed regarding decreased IgM levels in 22q11.2 deletion syndrome.

CONCLUSIONS

Fluorescence in situ hybridization analysis for chromosome 22q11.2 deletion should be considered in patients with selective IgM deficiency, especially if concurrent chronic otitis media, developmental delay, velopharyngeal insufficiency, or dysmorphic features are present.

Thymulin gene therapy prevents the reduction in circulating gonadotropins induced by thymulin deficiency in mice

Integrity of the thymus during perinatal life is necessary for a proper maturation of the pituitary-gonadal axis in mice and other mammalian species. Thus congenitally athymic (nude) female mice show significantly reduced levels of circulating gonadotropins, a fact that seems to be causally related to a number of reproductive derangements described in these mutants. Interestingly, a number of in vitro studies suggest that the thymic peptide thymulin may be involved in thymus-pituitary communication. To determine the consequences of low serum thymulin in otherwise normal animals, we induced short (8 days)- and long (33 days)-term thymulin deficiency in C57BL/6 mice by neonatally injecting (intraperitoneally) an anti-thymulin serum and assessed their circulating gonadotropin levels at puberty and thereafter. Control mice received an irrelevant antiserum. Gonadotropins were measured by radioimmunoassay and thymulin by bioassay. Both long- and short-term serum thymulin immunoneutralization resulted in a significant reduction in the serum levels of gonadotropins at 33 and 45 days of age. Subsequently, we injected (intramuscularly) an adenoviral vector harboring a synthetic DNA sequence (5'-ATGCAAGCCAAATCTCAAGGTGGATCCAACTAGTAG-3') encoding a biologically active analog of thymulin, methionine-FTS, in newborn nude mice (which are thymulin deficient) and measured circulating gonadotropin levels when the animals reached 52 days of age. It was observed that neonatal thymulin gene therapy in the athymic mice restored their serum thymulin levels and prevented the reduction in circulating gonadotropin levels that typically emerges in these mutants after puberty. Our results indicate that thymulin plays a relevant physiological role in the thymus-pituitary-gonadal axis.

Review of 54 patients with complete DiGeorge anomaly enrolled in protocols for thymus transplantation: outcome of 44 consecutive transplants

The purpose of this study was to characterize a large group of infants with complete DiGeorge anomaly and to evaluate the ability of thymus transplantation to reconstitute immune function in these infants. DiGeorge anomaly is characterized by varying defects of the heart, thymus, and parathyroid glands. Complete DiGeorge anomaly refers to the subgroup that is athymic (< 1%). The characteristics of 54 subjects at presentation and results from 44 consecutive thymus transplantations are reported. Remarkably, only 52% had 22q11 hemizygosity and only 57% had congenital heart disease requiring surgery. Thirty-one percent developed an atypical phenotype with rash and lymphadenopathy. To date, 33 of 44 subjects who received a transplant survive (75%) with post-transplantation follow-up as long as 13 years. All deaths occurred within 12 months of transplantation. All 25 subjects who were tested 1 year after transplantation had developed polyclonal T-cell repertoires and proliferative responses to mitogens. Adverse events developing after transplantation included hypothyroidism in 5 subjects and enteritis in 1 subject. In summary, diagnosis of complete DiGeorge anomaly is challenging because of the variability of presentation. Thymus transplantation was well tolerated and resulted in stable immunoreconstitution in these infants.

DiGeorge Syndrome/Velocardiofacial Syndrome: The Chromosome 22q11.2 Deletion Syndrome

Chromosome 22q11.2 deletion (CH22qD) syndrome is also known as DiGeorge syndrome or velocardiofacial syndrome. This deletion syndrome is extremely common with nearly one in 4000 children being affected. Recent advances and a holistic approach to patients have improved the care and well-being of these patients. This review will summarize advances in understanding the health needs and immune system of patients with CH22qD syndrome. Patients will most often need interventions directed at maximizing function for many organ systems but can ultimately have a high level of functioning.

Humoral immune responses and CD27+ B cells in children with DiGeorge syndrome (22q11.2 deletion syndrome)

The spectrum of T-cell abnormalities in 22q11.2 syndrome is quite broad, ranging from profound and life threatening to non-existent defects. Humoral abnormalities have been described in some of these patients, although no data are currently available on their phenotypical and functional B cell subsets. The purpose of this study was to investigate humoral immune function in a cohort of 13 children with DiGeorge syndrome by immunophenotyping B and by analysing their functionality in vivo. Humoral immunity was assessed by serum immunoglobulin evaluation, IgG subclasses determination, and testing of specific antibody titers to recall antigens. B cells were analyzed by flow cytometry and the relevant percentage of membrane surface expression of CD27, IgM, IgD was evaluated. In our cohort, one of 13 children (7.7%) had a complete IgA deficiency, four of 13 (30.7%) had minor immunoglobulin abnormalities, and five (38%) had an impaired production of specific antibodies. Five of 13 children (38%) had recurrent infections. Interestingly, peripheral CD27+ B cells were reduced in our patients as compared with age-matched healthy controls, and this decrement was statistically significant for IgM+ IgD+ CD27+ B cells. Immunoglobulin abnormalities were associated with the occurrence of recurrent infections. We conclude that a significant proportion of patients with DiGeorge syndrome have defective humoral immunity, which may represent an additional pathogenic mechanism underlying the increased susceptibility to infections. Whether the decreased CD27+ B-cell subset might be one of the defects that contribute to impaired humoral immunity, and to susceptibility to infection remains to be elucidated.

Syndromic immunodeficiencies: genetic syndromes associated with immune abnormalities

In syndromic immunodeficiencies, clinical features not directly associated with the immune defect are prominent. Patients may present with either infectious complications or extra-immune medical issues. In addition to the immunologic abnormality, a wide range of organ systems may be affected. Patients may present with disturbances in skeletal, neurologic, dermatologic, or gastrointestinal function or development. These conditions can be caused by developmental abnormalities, chromosomal aberrations, metabolic disorders, or teratogens. For a number of these conditions, recent advances have resulted in an enhanced understanding of their genetic basis. The finding of immune deficits in a number of defined syndromes with congenital anomalies suggests that an underlying genetic syndrome should be considered in those patients in whom a significant non-immune feature is present.

Update on primary immunodeficiency: defects of lymphocytes

The recent identification of the genes involved in many primary immunodeficiency disorders has led to a significant increase in our understanding of the pathogenesis of these defects. Many of these disorders share a clinical phenotype with common features such as recurrent infections, chronic inflammation, and autoimmunity. Although some of these immune defects have mild presentations and better outcomes, others result in severe infections and significant morbidity and mortality. For these, early diagnosis and treatment are critical. This review provides an overview of the genetic defects and clinical features of primary immune deficiencies due to defects in lymphocytes.

Deletion of chromosome 22q11.2 and outcome in patients with pulmonary atresia and ventricular septal defect

BACKGROUND

The 22q11.2 deletion (del22q) is present in many patients with conotruncal abnormalities including pulmonary atresia with ventricular septal defect (PA/VSD). We sought to determine the impact of the del22q on outcome in subjects with PA/VSD.

METHODS

We reviewed the experience for all patients with PA/VSD who were born between January 1993 and April 2002 and presented to our institution. Patients with conotruncal defects were routinely evaluated for genetic disorders including del22q. Fluorescence in situ hybridization was used to test for del22q.

RESULTS

There were 67 subjects with PA/VSD who presented during that time period; testing for del22q was performed in 58 of 67 (87%) and these 58 patients comprised the study population. The 22q11.2 deletion was present in 20 of 58 (34%) patients tested. Major aortopulmonary collaterals were defined by angiography and were present in 27 (47%). These collaterals were significantly more common among subjects with del22q (13 of 20, 65%; p = 0.04). The median cross sectional area of the pulmonary arteries, the Nakata index, was significantly less for patients with del22q (41 versus 142 mm(2)/m(2); p = 0.006). There were 3 subjects, all of whom had del22q, who did not undergo surgery owing to markedly hypoplastic pulmonary arteries. Of the remaining 55 patients, 53 had arteriopulmonary shunt with or without unifocalization as the initial procedure and 35 patients have undergone complete repair. There were 8 operative deaths and 1 nonoperative death. The 5-year survival was 36% for patients with del22q versus 90% for patients without del22q. The 22q11.2 deletion was a significant risk factor for death, even after adjusting for the presence of major aortopulmonary collaterals (p = 0.004). There was no significant difference between the two groups with respect to the incidence of serious viral, bacterial, or fungal infections in the perioperative period.

CONCLUSIONS

Patients with del22q and PA/VSD are at increased risk for death owing to a variety of factors including less favorable pulmonary artery anatomy. A better understanding of del22q, pulmonary artery anatomy, and outcome is required.

Long-term assessment of T-cell populations in DiGeorge syndrome

BACKGROUND

Patients with DiGeorge syndrome present with a broad range of T-cell deficiency. Partial DiGeorge syndrome (pDGS) is a preferred designation for patients with detectable T-cell function. Among immunology experts, there is no uniform opinion on the necessity of T-cell precautions for pDGS patients. Few studies have addressed the natural course of their immune function over time.

OBJECTIVE

The objective of this study was to describe the natural history of immune parameters in pDGS.

METHODS

We reviewed the medical records of 45 pDGS patients. Peripheral blood T-cell subsets counts and percentages were recorded at 1, 6, 12, 18, 24, 30, 48, 60, 72, 96, and 120 months of age, and the rates of change of T-cell measurements over the follow-up period (slopes) were calculated for each individual. Humoral immunity was evaluated by quantification of immunoglobulins and by testing antibody titers to recall antigens.

RESULTS

T-cell subsets counts from pDGS patients were generally lower than those of age-matched normal populations but were not severely depressed (ie, CD4+ T-cell percentage less than 15%). The median of the slopes for CD3+, CD4+, and CD8+ T-cell percentages were -0.7%, -0.8%, and -0.1%/month, respectively, in the first year of age and 0.1%/month for each subpopulation from 12 to 120 months of age. Lymphoproliferative responses to phytohemagglutinin were adequate at all ages. Immunoglobulin deficiencies or inadequate production of specific antibodies were not detected.

CONCLUSIONS

In our pDGS patient cohort, a significant deterioration of T-cell number or function did not occur over time. Clinical implications of this finding include the possibility of discontinuing T-cell deficiency precautions and frequency of reevaluations of pDGS patients with stable and adequate immune function.

Assessment of the thymus at echocardiography in fetuses at risk for 22q11.2 deletion

OBJECTIVES

An absent or hypoplastic thymus is common in patients with 22q11.2 deletion (del22q11.2). We sought to determine whether fetal echocardiography could identify absence of the thymus as a diagnostic tool in pregnancies at risk for fetal del22q11.2.

METHODS

We evaluated the fetal thymus in 16 consecutive pregnancies at risk for fetal del22q11. Fourteen of the fetuses had a conotruncal cardiac lesion, one had a twin with a conotruncal lesion, and in one the mother had a diagnosis of del22q11.2. The fetal thymus assessment was performed by an individual who was not aware of the del22q11.2 status of the fetus.

RESULTS

By 2D imaging, the thymus was identified in the anterosuperior mediastinum as a subtle hypoechogenic area. In nine cases, the thymus was demonstrated prenatally and none had del22q11.2. However, in one case the thymus was only seen on follow-up fetal echocardiography. In six cases, the thymus could not be identified and all six had del22q11.2. In one additional case, analyzed retrospectively, the thymus could not be assessed. The status of the thymus was confirmed on postnatal echocardiography or autopsy in 11 of the 15 cases assessed prenatally.

CONCLUSIONS

Our study suggests that fetal echocardiography can assess the thymus in most cases at risk for del22q11.2. This information may be useful in counseling women/couples who decline amniocentesis or who are awaiting amniocentesis results.

Antibody deficiency and autoimmunity in 22q11.2 deletion syndrome

BACKGROUND

Although severe T cell immunodeficiency in DiGeorge anomaly is rare, previous studies of humoral function in these patients have found no antibody abnormalities but have not examined the response to polysaccharide antigens. Isolated cases of autoimmunity have been reported. Several patients with 22q11.2 deletion attending our immunology clinic suffered recurrent sinopulmonary infection or autoimmune phenomena.

AIMS

To investigate humoral immunodeficiency, particularly pneumococcal polysaccharide antibody deficiency, and autoimmune phenomena in a cohort of patients with 22q11.2 deletion.

METHODS

A history of severe or recurrent infection and autoimmune symptoms were noted. Lymphocyte subsets, immunoglobulins, IgG subclasses, specific vaccine antibodies, and autoantibodies were measured. Subjects were vaccinated with appropriate antigens as indicated.

RESULTS

Of 32 patients identified, 26 (81%) had severe or recurrent infection, of which 13 (50%) had abnormal serum immunoglobulin measurements and 11/20 >/=4 years old (55%) had an abnormal response to pneumococcal polysaccharide. Ten of 30 patients (33%) had autoimmune phenomena; six (20%) were symptomatic.

CONCLUSIONS

Humoral immunodeficiency is more common than previously recognised in patients with 22q11.2 deletion. Normal T cell function and immunoglobulin levels do not exclude poor specific antibody responses. Patients should be referred for formal immunological assessment of cellular and humoral immune function.

Exposure of cynomolgus monkey embryos to retinoic acid causes thymic defects: effects on peripheral lymphoid organ development

We have previously reported that exposure of monkey embryos to 13-cis-retinoic acid (cRA) results in thymic defects. In this study, we analyzed lymphocyte and antigen-presenting cell populations at gestational days (GDs) 80-100 in the thymus, spleen, mesenteric lymph nodes, and gut-associated lymphoid tissue following a teratogenic dosing regimen of cRA (2.5 and 5 mg/kg) at GD14-27. Tissue sections were immunostained for T-cells (anti-CD3), B-cells (anti-CD20), dendritic cells (p55), and major histocompatibility class II (anti-HLA-DR). Digital images of spleen sections were analyzed to obtain the relative area occupied by the cell subsets within the white pulp (WP). Compared with controls, the T-cell dependent compartment of the spleen WP in specimens with perturbed thymic development (aplasia and severe hypoplasia) showed a reduction in size and proportion of CD3(+) T cells. Our findings indicate that cRA-induced thymic defects result in disrupted development of the splenic T-cell dependent compartment.

DiGeorge syndrome/chromosome 22q11.2 deletion syndrome

DiGeorge syndrome is characterized by conotruncal cardiac defects, hypocalcemia, and a hypoplastic thymus. Many, but not all, patients have a heterozygous deletion of chromosome 22q11.2. In its most severe form, it represents a devastating syndrome with high mortality. Patients with severe immunodeficiency are candidates for a thymic transplant or a fully matched bone marrow transplant. Fortunately, the majority of patients with either DiGeorge syndrome or chromosome 22q11.2 deletion syndrome have a mild to moderate immunodeficiency. These patients may develop recurrent infections or autoimmune disease.