Pulmonary diseases in children with severe combined immune deficiency and DiGeorge syndrome

Airway anomalies in patients with 22q11.2 deletion syndrome: A scoping review

OBJECTIVE

People with 22q11.2 deletion syndrome (22q11DS) can present with a wide variety of findings. Various airway anomalies have been described intermittently within this syndrome, but this feature has not been extensively investigated. Increased provider awareness of these findings may help guide clinical decision-making and improve overall patient outcomes. The objectives of this review are to identify the types of airway anomalies in 22q11DS and the prevalence of airway anomalies within symptomatic individuals.

METHODS

PubMed/MEDLINE, Cochrane Library, and EMBASE databases were searched in February 2022 for all available articles. Search terms included those that described 22q11DS or one of its synonymous conditions AND those that described airway anatomy and anomalies. The term airway anomaly was defined as any structural aberration in the conductive airway from the oral or nasal vestibule region to the mainstem bronchus. Studies were screened by two authors. A review of references was conducted. Eligible manuscripts underwent full-text review for quality appraisal and data extraction.

RESULTS

From a total of 909 unique manuscripts, 58 studies were selected, describing 328 people. The prevalence of airway anomaly diagnosis within symptomatic individuals ranged from 14% to 74%. Twenty-two unique airway anomalies were described. Laryngeal web was the most frequently described anomaly, followed by airway malacia and subglottic stenosis. Laryngeal web was 40% sensitive for suggesting a diagnosis of 22q11DS. Among affected individuals, as many as 46% had multiple concomitant airway anomalies. Aside from respiratory symptoms, other features that prompted airway evaluation included difficult intubation or failed extubation.

CONCLUSION

The findings within this review support the notion that a wide variety of airway anomalies may be seen in people with 22q11DS and that these findings have been discovered frequently in those with airway symptoms. Providers should maintain a low threshold to perform an airway examination in those with 22q11DS, especially when airway symptoms are present.

The lung in inborn errors of immunity: From clinical disease patterns to molecular pathogenesis

In addition to being a vital organ for gas exchange, the lung is a crucial immune organ continuously exposed to the external environment. Genetic defects that impair immune function, called inborn errors of immunity (IEI), often have lung disease as the initial and/or primary manifestation. Common types of lung disease seen in IEI include infectious complications and a diverse group of diffuse interstitial lung diseases. Although lung damage in IEI has been historically ascribed to recurrent infections, contributions from potentially targetable autoimmune and inflammatory pathways are now increasingly recognized. This article provides a practical guide to identifying the diverse pulmonary disease patterns in IEI based on lung imaging and respiratory manifestations, and integrates this clinical information with molecular mechanisms of disease and diagnostic assessments in IEI. We cover the entire IEI spectrum, including immunodeficiencies and immune dysregulation with monogenic autoimmunity and autoinflammation, as well as recently described IEI with pulmonary manifestations. Although the pulmonary manifestations of IEI are highly relevant for all age groups, special emphasis is placed on the pediatric population, because initial presentations often occur during childhood. We also highlight the pivotal role of genetic testing in the diagnosis of IEI involving the lungs and the critical need to develop multidisciplinary teams for the challenging evaluation of these rare but potentially life-threatening disorders.

Infectious Complications of DiGeorge Syndrome in the Setting of Malignancy

This report describes a case of a young man with DiGeorge Syndrome, repaired Tetralogy of Fallot, relapsed metastatic Hodgkin’s Lymphoma, immunodeficiency, and a history of recurrent and severe infections. A review of the literature indicates that patients with DiGeorge Syndrome are at greater risk for infection, malignancy, and cardiac events due to anatomic and immunologic complications resulting from a deletion in the 22q11.2 chromosome. As an increased number of patients with DiGeorge Syndrome are surviving into adulthood, it is important to understand the progression of the disease and the long-term implications associated with variable degrees of thymic hypoplasia and immune deficiency. 

Respiratory Infections in Patients with Primary Immunodeficiency

Recurrent and life-threatening respiratory infections are nearly universal in patients with primary immunodeficiency diseases (PIDD). Early recognition, aggressive treatment, and prophylaxis with antimicrobials and immunoglobulin replacement have been the mainstays of management and will be reviewed here with an emphasis on respiratory infections. Genetic discoveries have allowed direct translation of research to clinical practice, improving our understanding of clinical patterns of pathogen susceptibilities and guiding prophylaxis. The recent identification of inborn errors in type I interferon signaling as a basis for life-threatening viral infections in otherwise healthy individuals suggests another targetable pathway for treatment and/or prophylaxis. The future of PIDD diagnosis will certainly involve early genetic identification by newborn screening before onset of infections, with early treatment offering the potential of preventing disease complications such as chronic lung changes. Gene editing approaches offer tremendous therapeutic potential, with rapidly emerging delivery systems. Antiviral therapies are desperately needed, and specific cellular therapies show promise in patients requiring hematopoietic stem cell transplantation. The introduction of approved therapies for clinical use in PIDD is limited by the difficulty of studying outcomes in rare patients/conditions with conventional clinical trials.

Mycobacterial diseases in patients with inborn errors of immunity

Clinical disease caused by the agent of tuberculosis, Mycobacterium tuberculosis, and by less virulent mycobacteria, such as bacillus Calmette-Guérin (BCG) vaccines and environmental mycobacteria, can result from inborn errors of immunity (IEIs). IEIs underlie more than 450 conditions, each associated with an impairment of the development and/or function of hematopoietic and/or non-hematopoietic cells involved in host defense. Only a minority of IEIs confer predisposition to mycobacterial disease. The IEIs underlying susceptibility to bona fide tuberculosis are less well delineated than those responsible for susceptibility to less virulent mycobacteria. However, all these IEIs share a defining feature: the impairment of immunity mediated by interferon gamma (IFN-γ). More profound IFN-γ deficiency is associated with a greater vulnerability to weakly virulent mycobacteria, whereas more selective IFN-γ deficiency is associated with a more selective predisposition to mycobacterial disease. We review here recent progress in the study of IEIs underlying mycobacterial diseases.

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.

The monogenic basis of human tuberculosis

The pathogenesis of tuberculosis (TB) remains poorly understood, as no more than 5-10% of individuals infected with Mycobacterium tuberculosis go on developing clinical disease. The contribution of human genetics to TB pathogenesis has been amply documented by means of classic genetics since the turn of the twentieth century. Over the last 20 years, following-up on the study of Mendelian susceptibility to mycobacterial disease (MSMD), monogenic disorders have been found to underlie TB in some patients. Rare inborn errors of immunity, such as autosomal recessive, complete IL-12Rβ1 and TYK2 deficiencies, impairing the IL-12- and IL-23-dependent induction of IFN-γ, were initially identified in a few patients. More recently, homozygosity for a common variant of TYK2 (P1104A) that selectively disrupts cellular responses to IL-23 was found in two cohorts of TB patients. It shows high penetrance in areas endemic for TB and appears to be responsible for about 1% of TB cases in populations of European descent. Both rare and common genetic etiologies of TB affect IFN-γ immunity, providing a rationale for novel preventive and therapeutic approaches for TB control, including the use of recombinant IFN-γ.

Minor pulmonary malformations in a child

This case report describes an Italian female who was born at full term via Caesarean delivery, performed for breech presentation. She was the first child of healthy, unrelated parents. At birth, she weighed 2600 g (<3rd centile; −2 sd) and measured 45 cm in length (<3rd centile; −2 sd). Psychomotor development was normal for her age. The recommended immunisation schedule was administered. Newborn screening tests (hip ultrasound and acoustic reflexes) as well as echocardiography were normal. There was no known maternal exposure to teratogens or infections. The family history was unremarkable, except for retinitis pigmentosa and hypothyroidism (in the mother).

Can you diagnose this child with minor pulmonary malformations and recurrent pulmonary symptoms?http://ow.ly/6zQB30jHZAP

Recognition and Clinical Presentation of Invasive Fungal Disease in Neonates and Children

Invasive fungal diseases (IFDs) are devastating opportunistic infections that result in significant morbidity and death in a broad range of pediatric patients, particularly those with a compromised immune system. Recognizing them can be difficult, because nonspecific clinical signs and symptoms or isolated fever are frequently the only presenting features. Therefore, a high index of clinical suspicion is necessary in patients at increased risk of IFD, which requires knowledge of the pediatric patient population at risk, additional predisposing factors within this population, and the clinical signs and symptoms of IFD. With this review, we aim to summarize current knowledge regarding the recognition and clinical presentation of IFD in neonates and children.

Inherited and acquired immunodeficiencies underlying tuberculosis in childhood

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M.tb) and a few related mycobacteria, is a devastating disease, killing more than a million individuals per year worldwide. However, its pathogenesis remains largely elusive, as only a small proportion of infected individuals develop clinical disease either during primary infection or during reactivation from latency or secondary infection. Subacute, hematogenous, and extrapulmonary disease tends to be more frequent in infants, children, and teenagers than in adults. Life-threatening primary TB of childhood can result from known acquired or inherited immunodeficiencies, although the vast majority of cases remain unexplained. We review here the conditions conferring a predisposition to childhood clinical diseases caused by mycobacteria, including not only M.tb but also weakly virulent mycobacteria, such as BCG vaccines and environmental mycobacteria. Infections with weakly virulent mycobacteria are much rarer than TB, but the inherited and acquired immunodeficiencies underlying these infections are much better known. Their study has also provided genetic and immunological insights into childhood TB, as illustrated by the discovery of single-gene inborn errors of IFN-γ immunity underlying severe cases of TB. Novel findings are expected from ongoing and future human genetic studies of childhood TB in countries that combine a high proportion of consanguineous marriages, a high incidence of TB, and an excellent clinical care, such as Iran, Morocco, and Turkey.

Hereditary interstitial lung diseases manifesting in early childhood in Japan

BACKGROUND

Genetic variations associated with interstitial lung diseases (ILD) have not been extensively studied in Japanese infants.

METHODS

Forty-three infants with unexplained lung dysfunction were studied. All 43, 22, and 17 infants underwent analyses of surfactant protein (SP)-C gene (SFTPC) and ATP-binding cassette A3 gene (ABCA3), SP-B gene (SFTPB), and SP-B western blotting, respectively. Two and four underwent assessment of granulocyte macrophage colony-stimulating factor-stimulating phosphorylation of signal transducer and activator of transcription-5 (pSTAT-5) and analyses of FOXF1 gene (FOXF1), respectively.

RESULTS

ILD were diagnosed clinically in nine infants: four, three, and two had interstitial pneumonitis, hereditary pulmonary alveolar proteinosis (hPAP), and alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV), respectively. Genetic variations considered responsible were detected in six (67%) of the nine infants with ILD: three with hPAP (SFTPC p.Leu45Arg and p.Gln145fs, and ABCA3 p.Arg1583Trp/p.Val1495CysfsX21), two with interstitial pneumonitis (SFTPC p.Lys63Glu and p.Ser72Asn/p.Gly100Ala), and one with ACD/MPV (FOXF1 p.Leu300ArgfsX79). None showed SFTPB mutations or defects in pSTAT-5. The 17 bronchoalveolar lavage or tracheal aspirates contained enough SP-B protein.

CONCLUSION

The SP-C abnormality was most prevalent, and SP-B deficiency was rare in Japanese infants with hereditary ILD.

Cytomegalovirus pneumonia as the first manifestation of severe combined immunodeficiency

Severe combined immunodeficiency (SCID) is characterized by the absence of functional T lymphocytes and impairment of adaptive immunity. While heterogeneity of the genetic background in SCID leads to the variability of immune phenotypes, most of affected newborns appear healthy but within the first few months they develop life-threatening opportunistic respiratory or gastrointestinal tract infections. The objective of the study was to define the presenting features and etiology of infections in children with SCID. We retrospectively reviewed five children in whom the diagnosis of SCID had been established in our pediatric immunology clinic over the last 10-year period. A viral respiratory tract infection was the first manifestation of SCID in all the children studied. Cytomegalovirus (CMV) pneumonia was recognized in as many as 4 cases and coronavirus pulmonary infection was diagnosed in one case, whereas Pneumocystis jiroveci was identified as a co-pathogen in one CMV-infected patient. Severe combined immunodeficiency is a pediatric emergency condition and given the significant impact of pulmonary CMV infection in SCID children, establishing an accurate etiological diagnosis is of essential importance in instituting the specific treatment and improving the outcome.

Pneumothorax in patients with severe combined immunodeficiency

BACKGROUND

Most infants with pneumothorax have underlying conditions. Pneumocystis jirovecii pneumonia (PCP) frequently occurs in patients with severe combined immunodeficiency (SCID). The aim of this study was to determine clinical features of PCP-associated pneumothorax in SCID patients.

METHODS

The medical records of four SCID patients with pneumothorax were retrospectively reviewed.

RESULTS

All four patients were diagnosed as having SCID at the time of contracting PCP. All patients received mechanical ventilation because of severe respiratory failure. Only one patient was successfully extubated and was alive following hematopoietic stem cell transplantation (HSCT); of the remaining patients, however, two died of respiratory failure, and one patient died of early HSCT-related complications.

CONCLUSIONS

Pneumothorax associated with PCP can occur in SCID patients, and they may have a poor prognosis. If pneumothorax occurs in infants, both respiratory management and prompt investigation of the underlying conditions are needed, considering the possibility of PCP associated with SCID.

Inspiratory muscle strength training in infants with congenital heart disease and prolonged mechanical ventilation: a case report

BACKGROUND AND PURPOSE

Inspiratory muscle strength training (IMST) has been shown to improve maximal pressures and facilitate ventilator weaning in adults with prolonged mechanical ventilation (MV). The purposes of this case report are: (1) to describe the rationale for IMST in infants with MV dependence and (2) to summarize the device modifications used to administer training.

CASE DESCRIPTION

Two infants with congenital heart disease underwent corrective surgery and were referred for inspiratory muscle strength evaluation after repeated weaning failures. It was determined that IMST was indicated due to inspiratory muscle weakness and a rapid, shallow breathing pattern. In order to accommodate small tidal volumes of infants, 2 alternative training modes were devised. For infant 1, IMST consisted of 15-second inspiratory occlusions. Infant 2 received 10-breath sets of IMST through a modified positive end-expiratory pressure valve. Four daily IMST sets separated by 3 to 5 minutes of rest were administered 5 to 6 days per week. The infants' IMST tolerance was evaluated by vital signs and daily clinical reviews.

OUTCOMES

Maximal inspiratory pressure (MIP) and rate of pressure development (dP/dt) were the primary outcome measures. Secondary outcome measures included the resting breathing pattern and MV weaning. There were no adverse events associated with IMST. Infants generated training pressures through the adapted devices, with improved MIP, dP/dt, and breathing pattern. Both infants weaned from MV to a high-flow nasal cannula, and neither required subsequent reintubation during their hospitalization.

DISCUSSION

This case report describes pediatric adaptations of an IMST technique used to improve muscle performance and facilitate weaning in adults. Training was well tolerated in 2 infants with postoperative weaning difficulty and inspiratory muscle dysfunction. Further systematic examination will be needed to determine whether IMST provides a significant performance or weaning benefit.

Bacillus Calmette-Guérin (BCG) complications associated with primary immunodeficiency diseases

Primary immunodeficiency diseases (PIDs) are a group of inherited disorders, characterized by defects of the immune system predisposing individuals to variety of manifestations, including recurrent infections and unusual vaccine complications. There are a number of PIDs prone to Bacillus Calmette-Guérin (BCG) complications. This review presents an update on our understanding about the BCGosis-susceptible PIDs, including severe combined immunodeficiency, chronic granulomatous disease, and Mendelian susceptibility to mycobacterial diseases.

[22Q11 microdeletion syndrome: cardiorespiratory symptoms and fibrobronchoscopy]

The 22q11 deletion syndrome is a frequent contiguous-gene deletion syndrome. This disorder has a broad spectrum of phenotypic manifestations. It includes various syndromes such as DiGeorge syndrome. The most frequent clinical manifestations are congenital cardiac defects, characteristic facies, palate malformations, hypoparathyroidism, immunodeficiency due to thymic hypoplasia, growth retardation, and behavioural and psychiatric problems. Among the symptoms observed, many patients suffer from respiratory insufficiency or failure. The origin is often multifactorial. Structural airway abnormalities are frequently found in this syndrome. In many of these patients the malformation is mild or non-existent, and remains asymptomatic. However, in some cases it can cause a severe respiratory insufficiency, being diagnosed when other disorders are ruled out. These cases illustrate the importance of early visualisation of the airway by fibrobronchoscopy in the management of the patient with 22q11 deletion syndrome who has recurrent respiratory difficulties.

Outcomes and duration of Pneumocystis jiroveci pneumonia therapy in infants with severe combined immunodeficiency

This retrospective review of patients with severe combined immunodeficiency and Pneumocystis jiroveci pneumonia (PCP) evaluated the relationship between duration of therapy to treat PCP and overall survival. We found that 80% of patients receiving only 21 days of antibiotics survived to 12 months beyond hematopoietic cell transplant, whereas only 25% of patients who required longer treatment for PCP survived to stem cell engraftment.

Purine nucleoside phosphorylase deficiency with fatal course in two sisters

Purine nucleoside phosphorylase (PNP) deficiency is a rare combined immunodeficiency disorder presenting with clinically recurrent infections, failure to thrive, various neurological disorders, malignancies, and autoimmune diseases. Here, we report two sisters with a fatal course of PNP deficiency due to delay in diagnosis. The first patient developed a liver abscess by Aspergillus fumigatus and the second patient developed Mycobacterium tuberculosis complex lymphadenitis and probable pulmonary tuberculosis due to disseminated BCG infection. The patients also suffered from sclerosing cholangitis. Mutation analysis of the PNP gene from both sisters revealed a homozygous mutation for a G>A at nucleotide 349 (349 G>A transition), which changes alanine 117 to theronine in exon 4 (A117T). An increased awareness of early signs, symptoms, and abnormal laboratory findings of PNP deficiency will establish the early prognosis and treatment.

Pneumocystis pneumonia in children

Pneumocystis pneumonia (PCP) is a life-threatening infection in immunocompromised children with quantitative and qualitative defects in T lymphocytes. At risk are children with lymphoid malignancies, HIV infection, corticosteroid therapy, transplantation and primary immunodeficiency states. Diagnosis is established through direct examination or polymerase chain reaction (PCR) from respiratory secretions. Trimethoprim-sulphamethoxazole is used for initial therapy in most patients, while pentamidine, atovaquone, clindamycin plus primaquine, and dapsone plus trimethoprim are alternatives. Prophylaxis of high-risk patients reduces but does not eliminate the risk of PCP. Improved understanding of the pathogenesis of PCP is important for future advances against this life-threatening infection.

Severe respiratory syncytial virus (RSV) infection in infants with neuromuscular diseases and immune deficiency syndromes

Respiratory syncytial virus (RSV) is an important cause of lower respiratory tract infection (LRTI) in infants and children. There is growing evidence of severe RSV disease in infants with neuromuscular diseases and immune deficiency syndromes. Factors predisposing to a more severe course of RSV disease in neuromuscular diseases include the impaired ability to clear secretions from the airways due to ineffective cough, respiratory muscle weakness, high prevalence of gastro-oesophageal reflux and swallowing dysfunction which leads to aspiration. Similarly, pulmonary disease is a common presenting feature and complication of T-cell immunodeficiency. Infants with severe congenital and acquired immune deficiency syndromes may demonstrate prolonged viral shedding in RSV LRTI and are reported to have increased morbidity and mortality associated with RSV infection. Although not indicated in most guideline statements, palivizumab prophylaxis for these uncommon underlying conditions is under consideration by clinicians. Prospective studies are needed to determine the burden of RSV disease in these children.

Pediatric cough: children are not miniature adults

Pediatric cough-related issues, like most other conditions in particularly young children, share similarities but also have substantial important differences with adults. These can be understood from physiologically based domains simplified to (1) cough-specific, (2) general respiratory, (3) other direct systems such as the immune system, and (4) other general physiology. Among other reasons, these result in observed differences in etiology, management, and measurement of response between children and adults. For example, while empirical therapy for chronic cough is widely advocated for adults, it is not advocated for children. Indeed, there is some evidence that an empirical approach is potentially harmful; this is related to the use of medications and the delay in obtaining a correct diagnosis such as missed foreign body aspiration.

Respiratory infection in congenital cardiac disease. Hospitalizations in young children in Spain during 2004 and 2005: the CIVIC Epidemiologic Study

OBJECTIVES

To evaluate the rate of hospitalization for acute respiratory tract infection in children less than 24 months with haemodynamically significant congenital cardiac disease, and to describe associated risk factors, preventive measures, aetiology, and clinical course.

MATERIALS AND METHODS

We followed 760 subjects from October 2004 through April 2005 in an epidemiological, multicentric, observational, follow-up, prospective study involving 53 Spanish hospitals.

RESULTS

Of our cohort, 79 patients (10.4%, 95% CI: 8.2%-12.6%) required a total of 105 admissions to hospital related to respiratory infections. The incidence rate was 21.4 new admissions per 1000 patients-months. Significant associated risk factors for hospitalization included, with odds ratios and 95% confidence intervals shown in parentheses: 22q11 deletion (8.2, 2.5-26.3), weight below the 10th centile (5.2, 1.6-17.4), previous respiratory disease (4.5, 2.3-8.6), incomplete immunoprophylaxis against respiratory syncytial virus (2.2, 1.2-3.9), trisomy 21 (2.1, 1.1-4.2), cardiopulmonary bypass (2.0, 1.1-3.4), and siblings aged less than 11 years old (1.7, 1.1-2.9). Bronchiolitis (51.4%), upper respiratory tract infections (25.7%), and pneumonia (20%) were the main diagnoses. An infectious agent was found in 37 cases (35.2%): respiratory syncytial virus in 25, Streptococcus pneumoniae in 5, and Haemophilus influenzae in 4. The odds ratio for hospitalization due to infection by the respiratory syncytial virus increases by 3.05 (95% CI: 2.14 to 4.35) in patients with incomplete prophylaxis. The median length of hospitalization was 7 days. In 18 patients (17.1%), the clinical course of respiratory infection was complicated and 2 died.

CONCLUSIONS

Hospital admissions for respiratory infection in young children with haemodynamically significant congenital cardiac disease are mainly associated with non-cardiac conditions, which may be genetic, malnutrition, or respiratory, and to cardiopulmonary bypass. Respiratory syncytial virus was the most commonly identified infectious agent. Incomplete immunoprophylaxis against the virus increased the risk of hospitalization.

Hyper-IgE syndrome and autoimmunity in Mexican children

Hyper-IgE syndrome (HIES) is a primary immunodeficiency characterized by recurrent skin abscesses, recurrent pneumonia with pneumatocele formation, eczema, eosinophilia, and elevated levels of serum IgE. Patients with the autosomal recessive (AR) form of HIES appear to be prone to developing autoimmune diseases. We present two cases of HIES with autoimmune complications; one case was a product of a consanguineous marriage, the other one was a sporadic case. The first patient presented with recurrent episodes of erythema nodosum, warts, bronchiolitis obliterans and thrombocytopenia. The second patient developed glomerulonephritis resulting in endstage renal failure. She later developed malar rash, oral ulcers, cerebral infarcts with vasculitis and positive ANA, anti-dsDNA, and antiphospholipid antibodies. We discuss the dilemma in treating patients who present with both primary immunodeficiency and autoimmunity.

Host genetic factors and mycobacterial infections: lessons from single gene disorders affecting innate and adaptive immunity

This review summarizes the association of increased susceptibility to mycobacterial disease in patients with genetic defects affecting innate and adaptive immunity. The optimum function of CD4 T-cell and macrophage function is critically important for immunity against mycobacteria. Antibody, complement and neutrophil function is not required for effective anti-mycobacterial immunity.

T cells cause acute immunopathology and are required for long-term survival in mouse adenovirus type 1-induced encephalomyelitis

Infection of adult C57BL/6 (B6) mice with mouse adenovirus type 1 (MAV-1) results in dose-dependent encephalomyelitis. Utilizing immunodeficient mice, we analyzed the roles of T cells, T-cell subsets, and T-cell-related functions in MAV-1-induced encephalomyelitis. T cells, major histocompatibility complex (MHC) class I, and perforin contributed to acute disease signs at 8 days postinfection (p.i.). Acute MAV-1-induced encephalomyelitis was absent in mice lacking T cells and in mice lacking perforin. Mice lacking alpha/beta T cells had higher levels of infectious MAV-1 at 8 days, 21 days, and 12 weeks p.i., and these mice succumbed to MAV-1-induced encephalomyelitis at 9 to 16 weeks p.i. Thus, alpha/beta T cells were required for clearance of MAV-1. MAV-1 was cleared in mice lacking perforin, MHC class I or II, CD4+ T cells, or CD8+ T cells. Our results are consistent with a model in which either CD8+ or CD4+ T cells are sufficient for clearance of MAV-1. Furthermore, perforin contributed to MAV-1 disease but not viral clearance. We have established two critical roles for T cells in MAV-1-induced encephalomyelitis. T cells caused acute immunopathology and were required for long-term host survival of MAV-1 infection.

Genetic dissection of immunity to mycobacteria: the human model

Humans are exposed to a variety of environmental mycobacteria (EM), and most children are inoculated with live Bacille Calmette-Guérin (BCG) vaccine. In addition, most of the world's population is occasionally exposed to human-borne mycobacterial species, which are less abundant but more virulent. Although rarely pathogenic, mildly virulent mycobacteria, including BCG and most EM, may cause a variety of clinical diseases. Mycobacterium tuberculosis, M. leprae, and EM M. ulcerans are more virulent, causing tuberculosis, leprosy, and Buruli ulcer, respectively. Remarkably, only a minority of individuals develop clinical disease, even if infected with virulent mycobacteria. The interindividual variability of clinical outcome is thought to result in part from variability in the human genes that control host defense. In this well-defined microbiological and clinical context, the principles of mouse immunology and the methods of human genetics can be combined to facilitate the genetic dissection of immunity to mycobacteria. The natural infections are unique to the human model, not being found in any of the animal models of experimental infection. We review current genetic knowledge concerning the simple and complex inheritance of predisposition to mycobacterial diseases in humans. Rare patients with Mendelian disorders have been found to be vulnerable to BCG, a few EM, and M. tuberculosis. Most cases of presumed Mendelian susceptibility to these and other mycobacterial species remain unexplained. In the general population leprosy and tuberculosis have been shown to be associated with certain human genetic polymorphisms and linked to certain chromosomal regions. The causal vulnerability genes themselves have yet to be identified and their pathogenic alleles immunologically validated. The studies carried out to date have been fruitful, initiating the genetic dissection of protective immunity against a variety of mycobacterial species in natural conditions of infection. The human model has potential uses beyond the study of mycobacterial infections and may well become a model of choice for the investigation of immunity to infectious agents.

Elective bone marrow transplantation in a child with X-linked hyper-IgM syndrome presenting with acute respiratory distress syndrome

We describe a 10-month-old boy diagnosed with X-linked hyper-IgM syndrome (XHIM) after suffering from life-threatening acute respiratory distress syndrome (ARDS) caused by Pneumocystis carinii pneumonia (PCP), although his previous clinical history and first level laboratory tests investigating immunological function did not indicate immunodeficiency. When the patient's overall condition was good, elective bone marrow transplantation from an HLA-matched older brother was performed successfully. We describe how correct diagnosis and successful treatment were made possible thanks to the involvement of a network of specialists.

Mycobacterial diseases in primary immunodeficiencies

Primary immunodeficiency diseases comprise over 100 conditions, each associated with a variety of viral, bacterial, fungal and protozoan infections. M. tuberculosis and less virulent mycobacteria, such as bacille Calmette-Guérin vaccines and environmental non-tuberculous mycobacteria, may cause severe disease in patients with primary immunodeficiency diseases. However, no previous review has dealt with the issue of which primary immunodeficiency diseases predispose affected individuals to mycobacterial disease. This information is very useful, not only increasing our understanding of human immunity to mycobacteria, but also for the diagnostic investigation of patients with mycobacteriosis. We review here the medical literature on cases of mycobacterial disease in patients with primary immunodeficiency diseases.

[The child with recurrent infections: which screening for immunoe deficiency?]

A child with recurrent infections represents a challenge to the pediatrician who must identify, among a large number of repeatedly infected but nevertheless healthy children whose parents need to be reassured, the rare cases of potentially severe immune deficiency. This can be most successfully achieved through the measurement of IgA, IgG, and antibody titers to vaccine (tetanus, diphtheria, Haemophilus influenzae B) and exposure (pneumococcus) antigens. The presence of normal antibody responses makes it possible to rule out underlying immune deficiency in a sensitive and specific manner. Conversely, abnormally weak antibody responses identify the children who have to be referred without delay for further investigation of a potential immune defect. This article indicates for which pediatric patients an immunodeficiency screening should be considered, and how to analyze its results.

Structural airway anomalies in patients with DiGeorge syndrome: a current review

DiGeorge Syndrome is a genetic disorder characterized by either absence or hypoplasia of the thymus and the parathyroid glands. Patients with this syndrome also have a high incidence of cardiovascular malformations and facial dysmorphism. Structural airway anomalies have also been described, albeit infrequently. Tracheoesophageal fistula, short trachea with reduced numbers of tracheal rings, abnormal thyroid cartilage, laryngomalacia, tracheomalacia, and bronchomalacia have been recognized in these patients. We review all previously reported patients with DiGeorge syndrome and lower airway anomalies. In addition, we present 2 patients with DiGeorge syndrome who were each found to have an aberrant right tracheal bronchus. Structural airway anomalies can be a cause of morbidity and mortality in patients with DiGeorge syndrome. Prompt, thorough evaluation of the upper and lower airway in these patients is essential.

Oral manifestations of primary immunological diseases

BACKGROUND

Primary immunodeficiencies have many oral manifestations. The clinical presentation of these diseases demonstrates the roles of different immune cells for the maintenance of oral health.

METHODS

The authors reviewed selected literature describing systemic and oral manifestations of the primary immunodeficiencies published between 1966 and 1999.

RESULTS

The authors found that oral candidiasis and herpetic infections are seen frequently in patients with T-cell deficiencies, while patients with B-cell deficiencies are most susceptible to bacterial infections. Periodontitis and oral candidiasis are found in some, but not all, phagocyte deficiencies.

CONCLUSIONS

These findings demonstrate that T cells, B cells and phagocytes all have roles in oral immunity.

CLINICAL IMPLICATIONS

Acquired conditions that affect the immune system such as diabetes, alcoholism and acquired immunodeficiency syndrome, as well as certain medications, will affect oral defense mechanisms. The effects that acquired immunodeficiencies will have on oral health can be predicted from the oral manifestations of primary immunodeficiencies.

Unsuspected Pneumocystis carinii pneumonia at presentation of severe primary immunodeficiency

BACKGROUND

Pneumocystis carinii is an important pathogen in immunodeficiency but may be an unrecognised cause of respiratory compromise.

OBJECTIVES

To ascertain the incidence of P carinii pneumonia (PCP) at presentation of severe combined immunodeficiency (SCID), whether it had been diagnosed, and the effect of treatment on outcome.

SETTING

The supraregional paediatric bone marrow transplant unit for primary immunodeficiencies at Newcastle General Hospital.

METHODS

Retrospective case note review of infants referred with a diagnosis of SCID from 1992 to 1998.

RESULTS

Ten of 50 infants had PCP at presentation; only one was diagnosed before transfer. Eight were diagnosed by bronchoalveolar lavage and two by lung biopsy. In only one was P carinii identified in nasopharyngeal secretions. Five required ventilation for respiratory failure but all were successfully treated with co-trimoxazole and methylprednisolone with or without nebulised budesonide. Nine survived to bone marrow transplantation and four are long term survivors after bone marrow transplantation; no deaths were related to PCP.

CONCLUSIONS

PCP is a common presenting feature of SCID but is rarely recognised. Bronchoalveolar lavage or lung biopsy are needed for diagnosis. Treatment with co-trimoxazole is highly successful.