Diagnostic paradigm for evaluation of male patients with chronic granulomatous disease, based on the dihydrorhodamine 123 assay

Flow cytometry-based diagnostic approach for inborn errors of immunity: experience from Algeria

Purpose

In this study, we retrospectively reviewed the use of flow cytometry (FCM) in the diagnosis of inborn errors of immunity (IEIs) at a single center in Algeria. Sharing insights into our practical experience, we present FCM based diagnostic approaches adapted to different clinical scenarios.

Methods

Between May 2017 and February 2024, pediatric and adult patients presenting with clinical features suggestive of immunodeficiency were subjected to FCM evaluation, including lymphocyte subset analysis, detection of specific surface or intracellular proteins, and functional analysis of immune cells.

Results

Over a nearly seven-year period, our laboratory diagnosed a total of 670 patients (372 (55.5%) males and 298 (44.5%) females), distributed into 70 different IEIs belonging to 9 different categories of the International Union of Immunological Societies classification. FCM was used to diagnose and categorize IEI in 514 patients (76.7%). It provided direct diagnostic insights for IEIs such as severe combined immunodeficiency, Omenn syndrome, MHC class II deficiency, familial hemophagocytic lymphohistiocytosis, and CD55 deficiency. For certain IEIs, including hyper-IgE syndrome, STAT1-gain of function, autoimmune lymphoproliferative syndrome, and activated PI3K delta syndrome, FCM offered suggestive evidence, necessitating subsequent genetic testing for confirmation. Protein expression and functional assays played a crucial role in establishing definitive diagnoses for various disorders. To setup such diagnostic assays at high and reproducible quality, high level of expertise is required; in house reference values need to be determined and the parallel testing of healthy controls is highly recommended.

Conclusion

Flow cytometry has emerged as a highly valuable and cost-effective tool for diagnosing and studying most IEIs, particularly in low-income countries where access to genetic testing can be limited. FCM analysis could provide direct diagnostic insights for most common IEIs, offer clues to the underlying genetic defects, and/or aid in narrowing the list of putative genes to be analyzed.

Chronic Granulomatous Disease (CGD): Commonly Associated Pathogens, Diagnosis and Treatment

Chronic granulomatous disease (CGD) is a primary immunodeficiency caused by a defect in the phagocytic function of the innate immune system owing to mutations in genes encoding the five subunits of the nicotinamide adenine dinucleotide phosphatase (NADPH) oxidase enzyme complex. This review aimed to provide a comprehensive approach to the pathogens associated with chronic granulomatous disease (CGD) and its management. Patients with CGD, often children, have recurrent life-threatening infections and may develop infectious or inflammatory complications. The most common microorganisms observed in the patients with CGD are Staphylococcus aureus, Aspergillus spp., Candida spp., Nocardia spp., Burkholderia spp., Serratia spp., and Salmonella spp. Antibacterial prophylaxis with trimethoprim-sulfamethoxazole, antifungal prophylaxis usually with itraconazole, and interferon gamma immunotherapy have been successfully used in reducing infection in CGD. Haematopoietic stem cell transplantation (HCT) have been successfully proven to be the treatment of choice in patients with CGD.

Inborn Errors of Immunity: A Role for Functional Testing and Flow Cytometry in Aiding Clinical Diagnosis

With the exponential discovery of new inborn errors of immunity (IEI), it is becoming increasingly difficult to differentiate between a number of the more recently defined disorders. This is compounded by the fact that although IEI primarily present with immunodeficiency, the spectrum of disease is broad and often extends to features typical of autoimmunity, autoinflammation, atopic disease, and/or malignancy. Here we use case studies to discuss the laboratory and genetic tests used that ultimately led to the specific diagnoses.

Diagnostic Modalities in Primary Immunodeficiency

As the field of inborn errors of immunity expands, providers continually update and fine-tune their diagnostic approach and selection of testing modalities to increase diagnostic accuracy. Here, we first describe a mechanistic consideration of laboratory testing, highlighting both benefits and drawbacks of currently clinically available testing modalities. Next, we provide methods in evaluation of patients presenting with concern for inborn errors of immunity as defined by the International Union of Immunological Societies 2019 phenotypic categories: primary antibody deficiencies, cellular and humoral immune deficiency, disorders of the innate immune system, and syndrome-associated and primary immune regulation disorders (PIRDs). Using the suggested approach in this paper as a roadmap highlights the importance of thorough history taking and physical examination as the foundation to guide further diagnostic tests. This is followed by enumeration and functional testing. Finally, to determine the underlying molecular etiology-specific genetic panels, chromosomal microarrays, and broad genetic testing (whole exome sequencing or whole genome sequencing) are available.

Case report: Chronic granulomatous disease presenting with early-onset inflammatory bowel disease and normal oxidative burst testing

BACKGROUND

Due to the lack of widespread availability of flow cytometry services for immunodeficiency, nitroblue tetrazolium test (NBT) is the commonly used screening modality to identify patients with chronic granulomatous disease (CGD) in developing countries.

PROCEDURE

We report a child with X-linked CGD with residual NADPH oxidase activity who had an indeterminate NBT result even in the presence of classical manifestations of CGD.

RESULTS

A 7-year-old boy presented with recurrent episodes of inflammatory colitis and Burkholderia cepacia septicaemia at the age of 3 years. He also had cervical adenitis due to Mycobacterium tuberculosis. NBT performed on multiple occasions was not suggestive of CGD. Dihydrorhodamine (DHR) test using phorbol myristate acetate (PMA) as a stimulant revealed a small blunt peak suggestive of AR-CGD; however, significant reduction in NADPH oxidase activity was noted with milder stimulants such as Escherichia coli and Staphylococcus aureus. Genetic analysis revealed a hemizygous pathogenic variant in CYBB. Flow cytometry showed diminished gp91phox expression in the patient's neutrophils suggestive of X-linked CGD.

CONCLUSION

Our case highlights that early-onset inflammatory bowel disease can be a presenting manifestation of CGD and diagnosis of CGD can be missed if NBT alone is used for screening, especially in the presence of NADPH oxidase activity. Diagnosis of "CGD with residual NADPH oxidase activity" requires a high degree of clinical suspicion, and performing DHR with different stimulants can unravel the diagnosis.

Utility of Immunohistochemistry and Immunofluorescence in Determining the Pathogenic Variants of Chronic Granulomatous Disease

BACKGROUND

Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder of phagocytes due to defects in any of the five subunits of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. An initial diagnosis of CGD is made by flow cytometry-based dihydrorhodamine assay or nitro blue tetrazolium test, which is further confirmed by molecular assays. Expression of five subunits of NADPH oxidase components by either flow cytometric or western blot analysis provides clues toward the potential gene targets which are subsequently confirmed by various genetic assays. Immunohistochemistry (IHC) and immunofluorescence (IF) have never been earlier used to determine the expression of different subunits of NADPH oxidase system. We evaluated the utility of IHC and IF in determining the underlying pathogenic variants of CGD.

MATERIALS AND METHODS

Twelve genetically confirmed cases of CGD, comprising of biopsy specimens (n = 6), tissue blocks from autopsy cases (n = 3), and cellblocks of cell pellet prepared from peripheral blood (n = 4) were included. IHC for p67phox and p47phox subunits and IF for cytochrome b558 were performed.

RESULTS

All 4 cases with pathogenic variation of NCF2 gene showed loss of expression for p67phox subunit. Two cases with pathogenic variation of NCF1 gene showed loss of expression for p47phox subunit. Five cases, except a single case with CYBB gene pathogenic variation, showed loss of expression for cytochrome b558 on IF. Thus, loss of expression consistently matched with the underlying genetic defects assessed by sequencing.

CONCLUSIONS

Our results confirm our hypothesis that IHC and IF are two rapid, economical, pathologist-friendly techniques providing pertinent information regarding the underlying pathogenic variants and such immuno-analysis can be easily performed on the tissue.

Clinical Features of Female Taiwanese Carriers with X-linked Chronic Granulomatous Disease from 2004 to 2019

PURPOSE

Female carriers with X-linked chronic granulomatous disease (XL-CGD) who have < 10% reactive oxygen species (ROS) production due to profound X-chromosome inactivation (XCI or lyonization) are more susceptible to infections. We assessed ROS production in Taiwanese female carriers with XL-CGD to investigate whether the level of ROS correlated to their clinical features of infection, autoimmunity, and autoinflammation.

METHODS

Clinical course, ROS production, flavocytochrome b558 (Cyto b558) expression, and genetic analysis in carriers were investigated after identifying their index cases between 2004 and 2019.

RESULTS

A total of 19 mothers (median 27 years; range 25-60 years) and three of four girls (range 4-6 years) relative to 22 male index XL-CGD cases from 19 unrelated families were enrolled. Approximately half (8/19, 42%) of the mothers had novel one-allele mutations. Twenty-two of the 23 females were carriers. One carrier with de novo [Arg290X]CYBB who suffered from refractory salmonella sepsis and chorioretinitis as an XL-CGD phenotype had extreme XCI, absent Cyto b558 expression, and only 8% ROS production. The remaining carriers had bimodal patterns of Cyto b558 expressions (median 40.2%, 26.8-52.4%) and ROS production (38.3%, range 28.2-54.2%) sufficient to prevent significant infections, although neck lymphadenitis recurred in one mother and sister who had ROS expressions of 28.2% and 38.0%, respectively. However, none of the carriers had manifestations of autoimmunity or autoinflammation (e.g., photosensitivity, aphthous stomatitis, or joint disorders), of which each was seen in approximately one-third of XL-CGD carriers from the Western world.

CONCLUSION

One carrier had undetectable Cyto b558 expression and an extremely low ROS production, and consequently presented with an XL-CGD phenotype. One mother and her daughter experienced recurrent neck lymphadenitis despite having sufficient ROS production. Significant autoimmunity/autoinflammation did not develop in any of the carriers. Studies with a longer follow-up period are needed to validate our findings.

Clinical and Laboratory Profiles of 17 Cases of Chronic Granulomatous Disease in North India

A primary immune deficiency disorder is often suspected in children with recurrent deep seated and fungal infections and those admitted to pediatric intensive care units. Chronic granulomatous disease (CGD) is inherited disorder leading to infections caused due to defective superoxide production. Cases referred for testing for a primary immunodeficiency disorder were tested for Dihydrorhodamine 123 (DHR) assay by flow cytometry and nitroblue tetrazolium dye (NBT) slide test. The unstimulated and stimulated samples were tested for oxidative burst activity which gives bright fluorescence due to formation of Rhodamine 123 on flow cytometry and blue formazan pigment in NBT slide test. The test results were reported in real time. From a total of 330 patients screened for chronic granulomatous disease using DHR and NBT slide test, 17 patients (5.1%) were found to have CGD. These included 12 boys and 5 girls. They presented with deep seated infections, recurrent and multiple abscess, recurrent pneumonia and granulomatous lymphadenitis. The causative organisms were Mycobacteriae, Staphylococcus, Burkholderia cepacia, Pseudomonas, Aspergillus and Cytomegalovirus. In 6 out of 17 positive cases family studies were carried out. On follow up five children succumbed to disease, two patients underwent allogeneic bone marrow transplant, the chimerism status was demonstrated by repeat DHR assay at day 50 post-transplant. Rest are in follow up under prophylactic antibiotics and supportive care. As facilities for molecular testing are not easily available for primary immuno deficiency disorders, flow cytometry based clinical laboratories can help to screen for some of the frequently suspected disorders like chronic granulomatous disease. This has aided in paediatric care in our centre.

Laboratory Assays of Immune Cell Function in Immunodeficiencies

Laboratory assays of immune cell function are essential for understanding the type and function of immune defects. These assessments should be performed in conjunction with a detailed history and physical examination, which should guide the evaluation of patients with a suspected immune deficiency. Laboratory assays of immune cell function are critical for assessing and demonstrating the functional impact of genetic mutations. Advances in diagnostic techniques continue to expand the ability of clinicians and researchers to understand the complex immune pathophysiology that underlies these disorders.

Application of Flow Cytometry in Primary Immunodeficiencies: Experience From India

Primary immunodeficiency diseases (PID) are a clinically and immunologically heterogeneous group of disorders of immune system. Diagnosis of these disorders is often challenging and requires identification of underlying genetic defects, complemented by a comprehensive evaluation of immune system. Flow cytometry, with its advances in the last few decades, has emerged as an indispensable tool for enumeration as well as characterization of immune cells. Flow cytometric evaluation of the immune system not only provides clues to underlying genetic defects in certain PIDs and helps in functional validation of novel genetic defects, but is also useful in monitoring immune responses following specific therapies. India has witnessed significant progress in the field of flow cytometry as well as PID over last one decade. Currently, there are seven Federation of Primary Immunodeficiency Diseases (FPID) recognized centers across India, including two Indian Council of Medical research (ICMR) funded centers of excellence for diagnosis, and management of PIDs. These centers offer comprehensive care for PIDs including flow cytometry based evaluation. The key question which always remains is how one selects from the wide array of flow cytometry based tests available, and whether all these tests should be performed before or after the identification of genetic defects. This becomes crucial, especially when resources are limited and patients have to pay for the investigations. In this review, we will share some of our experiences based on evaluation of a large cohort of hemophagocytic lymphohistiocytosis, severe combined immunodeficiency, and chronic granulomatous disease, and the lessons learned for optimum use of this powerful technology for diagnosis of these disorders.

A Novel Mutation in Chronic Granulomatous Disease: Treating the Family, Not Just the Patient

Chronic Granulomatous Disease (CGD) is caused by genetic defects in the phagocyte NADPH oxidase leading to potentially severe infections with catalase positive micro-organisms. With the innate immune system being affected this disease usually presents before the age of 5 years with infections involving the skin, lung, liver or lymphnodes. Infections with specific catalase positive organisms, especially Burkholderia cepacia, Serratia, Nocardia and Chromobacterium violaceum prompt a workup for CGD in affected patients. In addition, a family history of CGD also warrants testing. The pattern of inheritance of CGD varies across geographic regions of the world and societies, with X-linked inheritance being most prevalent in the United States and Europe. Affected patients require life-long therapy with prophylactic antibiotics, antifungals, and possibly interferon-gamma. Hematopoietic Stem Cell Transplantation is the only curative therapy known to date. Identification, diagnosis and management of patients with CGD usually involves a multi-specialty team including Pediatrics, Immunology, Infectious Diseases, Hematology/Oncology and often also Pulmonology and GI/Hepatology. Frequent follow up is paramount for good outcomes; infections have to be recognized and treated promptly and often preemptively. This is challenging for most patients and their families but presents a significant barrier for patients with limited access to care, limited resources or other challenging social situations. This case report describes the difficulties of managing a family with a novel mutation and multiple affected family members in different custody arrangements. It highlights the importance of close contact and communication with the family in deciding on management and treatment options. Educating the family and patient is critical to avoid complications of the disease and allow shared decision making that ultimately leads to better outcomes.

DUOX Defects and Their Roles in Congenital Hypothyroidism

Extracellular hydrogen peroxide is required for thyroperoxidase-mediated thyroid hormone synthesis in the follicular lumen of the thyroid gland. Among the NADPH oxidases, dual oxidases, DUOX1 and DUOX2, constitute a distinct subfamily initially identified as thyroid oxidases, based on their level of expression in the thyroid. Despite their high sequence similarity, the two isoforms present distinct regulations, tissue expression, and catalytic functions. Inactivating mutations in many of the genes involved in thyroid hormone synthesis cause thyroid dyshormonogenesis associated with iodide organification defect. This chapter provides an overview of the genetic alterations in DUOX2 and its maturation factor, DUOXA2, causing inherited severe hypothyroidism that clearly demonstrate the physiological implication of this oxidase in thyroid hormonogenesis. Mutations in the DUOX2 gene have been described in permanent but also in transient forms of congenital hypothyroidism. Moreover, accumulating evidence demonstrates that the high phenotypic variability associated with altered DUOX2 function is not directly related to the number of inactivated DUOX2 alleles, suggesting the existence of other pathophysiological factors. The presence of two DUOX isoforms and their corresponding maturation factors in the same organ could certainly constitute an efficient redundant mechanism to maintain sufficient H₂O₂ supply for iodide organification. Many of the reported DUOX2 missense variants have not been functionally characterized, their clinical impact in the observed phenotype remaining unresolved, especially in mild transient congenital hypothyroidism. DUOX2 function should be carefully evaluated using an in vitro assay wherein (1) DUOXA2 is co-expressed, (2) H₂O₂ production is activated, (3) and DUOX2 membrane expression is precisely analyzed.

Approach to Molecular Diagnosis of Chronic Granulomatous Disease (CGD): an Experience from a Large Cohort of 90 Indian Patients

BACKGROUND

Chronic granulomatous disease (CGD) is characterized by mutation in any one of the five genes coding NADPH oxidase components that leads to functional abnormality preventing the killing of phagocytosed microbes by affecting the progression of a respiratory burst. CGD patients have an increased susceptibility to infections by opportunistic and pathogenic organisms. Though initial diagnosis of CGD using a nitroblue tetrazolium (NBT) test or dihydrorhodamine (DHR) test is relatively easy, molecular diagnosis is challenging due to involvement of multiple genes, presence of pseudogenes, large deletions, and GC-rich regions, among other factors. The strategies for molecular diagnosis vary depending on the affected gene and the mutation pattern prevalent in the target population. There is a paucity of molecular data related to CGD for Indian population.

METHOD

This report includes data for a large cohort of CGD patients (n = 90) from India, describing the diagnostic approach, mutation spectrum, and novel mutations identified. We have used mosaicism in mothers and the expression pattern of different NADPH components by flow cytometry as a screening tool to identify the underlying affected gene. The techniques like Sanger sequencing, next-generation sequencing (NGS), and Genescan analysis were used for further molecular analysis.

RESULT

Of the total molecularly characterized patients (n = 90), 56% of the patients had a mutation in the NCF1 gene, 30% had mutation in the CYBB gene, and 7% each had mutation in the CYBA and NCF2 genes. Among the patients with NCF1 gene mutation, 82% of the patients had 2-bp deletion (DelGT) mutations in the NCF1 gene. In our cohort, 41 different mutations including 9 novel mutations in the CYBB gene and 2 novel mutations each in the NCF2, CYBA, and NCF1 genes were identified.

CONCLUSION

Substantial number of the patients lack NCF1 gene on both the alleles. This is often missed by advanced molecular techniques like Sanger sequencing and NGS due to the presence of pseudogenes and requires a simple Genescan method for confirmation. Thus, the diagnostic approach may depend on the prevalence of affected genes in respective population. This study identifies potential gene targets with the help of flow cytometric analysis of NADPH oxidase components to design an algorithm for diagnosis of CGD in India. In Indian population, the Genescan method should be preferred as the primary molecular test to rule out NCF1 gene mutations prior to Sanger sequencing and NGS.

Sex Differences in Acute Neuroinflammation after Experimental Traumatic Brain Injury Are Mediated by Infiltrating Myeloid Cells

The inflammatory response to moderate-severe controlled cortical impact (CCI) in adult male mice has been shown to exhibit greater glial activation compared with age-matched female mice. However, the relative contributions of resident microglia and infiltrating peripheral myeloid cells to this sexually dimorphic neuroinflammatory responses remains unclear. Here, 12-week-old male and female C57Bl/6 mice were subjected to sham or CCI, and brain samples were collected at 1, 3, or 7 days post-injury for flow cytometry analysis of cytokines, reactive oxygen species (ROS), and phagocytosis in resident microglia (CD45^intCD11b+) versus infiltrating myeloid cells (CD45^hiCD11b+). Motor (rotarod, cylinder test), affect (open field), and cognitive (Y-maze) function tests also were performed. We demonstrate that male microglia had increased phagocytic activity and higher ROS levels in the non-injured brain, whereas female microglia had increased production of tumor necrosis factor (TNF) α and interleukin (IL)-1β. Following CCI, males showed a significant influx of peripheral myeloid cells by 1 day post-injury followed by proliferation of resident microglia at 3 days. In contrast, myeloid infiltration and microglial activation responses in female CCI mice were significantly reduced. No sex differences were observed for TNFα, IL-1β, transforming growth factor β, NOX2, ROS production, or phagocytic activity in resident microglia or infiltrating cells at any time. However, across these functions, infiltrating myeloid cells were significantly more reactive than resident microglia. Female CCI mice also had improved motor function at 1 day post-injury compared with male mice. Thus, we conclude that sexually dimorphic responses to moderate-severe CCI result from the rapid activation and infiltration of pro-inflammatory myeloid cells to brain in male, but not female, mice.

Flow cytometry: Surface markers and beyond

Flow cytometry is a routinely available laboratory method to study cells in suspension from a variety of human sources. Application of this technology as a clinical laboratory method has evolved from the identification of cell-surface proteins to characterizing intracellular proteins and providing multiple different techniques to assess specific features of adaptive and innate immune function. This expanded menu of flow cytometric testing approaches has increased the utility of this platform in characterizing and diagnosing disorders of immune function.

Characterization of 4 New Mutations in the CYBB Gene in 10 Iranian Families With X-linked Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is an inherited disease of the innate immune system that results from defects in 1 of the 5 subunits of nicotinamide adenine dinucleotide phosphate oxidase complex and leads to life-threatening infections with granuloma formation. During 3 years of study, we recognized 10 male patients with X-linked CGD from a tertiary referral center for immune deficiencies in Iran. The CGD patients were diagnosed according to clinical features and biochemical tests, including nitroblue tetrazolium and dihydrorhodamine-1, 2, 3 tests, performed on patients and their mothers. In all patients, Western blot analysis showed a gp91 phenotype. Mutation screening by single strand conformation polymorphism and multiplex ligation-dependent probe amplification analysis of the CYBB gene encoding gp91, followed by sequencing, showed 9 different mutations, 4 of them novel as far as we know.

Correlation between flow cytometry and molecular findings in autosomal recessive chronic granulomatous disease: A cohort study from Oman

BACKGROUND

Chronic granulomatous disease (CGD) is an X-linked (XL) or autosomal recessive (AR) primary immunodeficiency disease. Respiratory burst assessment by flow cytometry is a rapid test of granulocyte stimulation, and results predict the underlying genotype. This study aims to describe the immune-phenotypic profile of patients with CGD diagnosed in our center and correlate that with underlying genetic mutations.

METHODS

Immuno-phenotypic and genetic data on all patients with CGD diagnosed at Sultan Qaboos University Hospital (SQUH) were reviewed.

RESULTS

A total of 32 patients were diagnosed with CGD using molecular studies. Genetically confirmed individuals included 1 patient with XL-CGD (a large deletion involving the CYBB and XK genes resulting in a McLeod phenotype), 27 patients with AR-CGD with a c.579G>A (p.Trp193X) mutation at the NCF1 gene, and 4 patients with AR-CGD with a c.784G>A (p.Gly262Ser) mutation at the NCF1 gene. Flow cytometry and molecular results were available for comparison in 26 patients with AR-CGD. The patients with AR-CGD had a range of flow cytometry-generated fluorescent patterns as follows: reduced neutrophil stimulation with a sharp peak (12/26), reduced neutrophil stimulation with a broad peak (11/26), and a complete lack of neutrophil stimulation (3/26). No consistent flow cytometry-generated fluorescent pattern was observed in either of the 2 AR mutations identified in our patients.

CONCLUSION

Flow cytometry is a robust test of CGD diagnosis. However, results should be interpreted with caution when predicting the underlying probable genotype, and results need to be complemented with definitive molecular studies.

X-Linked Chronic Granulomatous Disease: Initial Presentation with Intracranial Hemorrhage from Vitamin K Deficiency in Infant

Vitamin K deficiency bleeding (VKDB) is a life-threatening condition and can be found in children as early as neonatal period with early onset intracranial hemorrhage (ICH). Here, we reported a 1-year-old boy who initially presented with intracranial hemorrhage secondary to vitamin K deficiency since 3 months of age and later found to have XL-CGD which was complicated by malabsorption due to severe vaccine-associated mycobacterial disease.

CRISPR/Cas9-mediated modification of the extreme C-terminus impairs PDGF-stimulated activity of Duox2

Duox2 belongs to the large family of NADPH-oxidase enzymes that are implicated in immune response, vasoregulation, hormone synthesis, cell growth and differentiation via the regulated synthesis of H2O2 and reactive oxygen species. We and others have shown that Duox2 and H2O2 are involved in platelet-derived growth factor (PDGF) induced migration of fibroblasts. Now, using the CRISPR/Cas9-mediated genome editing we demonstrate that the extreme C-terminal region of Duox2 is required for PDGF-stimulated activity of Duox2 and H2O2 production. We generated the fibroblast cells that stably co-express the wild-type or C-terminally modified Duox2 and fluorescent H2O2 probe Hyper. We found that nonsense substitution of the last 23 amino acids in Duox2 results in complete loss of PDGF stimulation of intracellular H2O2 and fibroblast migration, yet these mutations have no effects on the expression of Duox2 and other NADPH-oxidases in cells. These findings illustrate for the first time that the extreme C-terminus of Duox2 is required for the functional activity of the enzyme. Furthermore, the conservative nature of the C-terminus suggests its role for activity in other NADPH-oxidases.

Overview of Infections in the Immunocompromised Host

Understanding the components of the immune system that contribute to host defense against infection is key to recognizing infections that are more likely to occur in an immunocompromised patient. In this review, we discuss the integrated system of physical barriers and of innate and adaptive immunity that contributes to host defense. Specific defects in the components of this system that predispose to particular infections are presented. This is followed by a review of primary immunodeficiency diseases and secondary immunodeficiencies, the latter of which develop because of a specific illness or condition or are treatment-related. The effects of treatment for neoplasia, autoimmune diseases, solid organ and stem cell transplants on host defenses are reviewed and associated with susceptibility to particular infections. In conclusion, an approach to laboratory screening for a suspected immunodeficiency is presented. Knowledge of which host defects predispose to specific infections allows clinicians to prevent, diagnose, and manage infections in their immunocompromised patients most effectively.

Application of Flow Cytometry in the Evaluation of Primary Immunodeficiencies

Primary immunodeficiency disorders (PIDDs) are a heterogeneous group of inherited disorders of the immune system. Currently more than 250 different PIDDs with a known genetic defect have been recognized. The diagnosis of many of these disorders is supported strongly by a wide variety of flow cytometry applications. Flow cytometry offers a rapid and sensitive tool for diagnosis and classification of PIDDs. It is applicable in the initial workup and subsequent management of several primary immunodeficiency diseases. As our understanding of the pathogenesis and management of these diseases increases, the majority of these tests can be easily established in the diagnostic laboratory. Thus, the focus of this article is on the application of flow cytometry in the diagnosis and/or evaluation of PIDDs.

Utility of fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography in a child with chronic granulomatous disease

We report the fluorodeoxyglucose positron emission tomography/computed tomography (FDG - PET/CT) findings in an 11-month-old boy with suspected milk protein allergy, presented to the hospital with 2-month history of fever of unknown origin and failure to thrive. It showed FDG avid lymphadenopathy above and below the diaphragm and splenic focus, which could represent diffuse inflammatory process or lymphoma. Subsequent jejunal biopsy showed non-necrotizing granulomas.

Clinical and Genotypic Spectrum of Chronic Granulomatous Disease in 71 Latin American Patients: First Report from the LASID Registry

AIM

We analyzed data from 71 patients with chronic granulomatous disease (CGD) with a confirmed genetic diagnosis, registered in the online Latin American Society of Primary Immunodeficiencies (LASID) database.

RESULTS

Latin American CGD patients presented with recurrent and severe infections caused by several organisms. The mean age at disease onset was 23.9 months, and the mean age at CGD diagnosis was 52.7 months. Recurrent pneumonia was the most frequent clinical condition (76.8%), followed by lymphadenopathy (59.4%), granulomata (49.3%), skin infections (42%), chronic diarrhea (41.9%), otitis (29%), sepsis (23.2%), abscesses (21.7%), recurrent urinary tract infection (20.3%), and osteomyelitis (15.9%). Adverse reactions to bacillus Calmette-Guérin (BCG) vaccination were identified in 30% of the studied Latin American CGD cases. The genetic diagnoses of the 71 patients revealed 53 patients from 47 families with heterogeneous mutations in the CYBB gene (five novel mutations: p.W361G, p.C282X, p.W483R, p.R226X, and p.Q93X), 16 patients with the common deletion c.75_76 del.GT in exon 2 of NCF1 gene, and two patients with mutations in the CYBA gene.

CONCLUSION

The majority of Latin American CGD patients carry a hemizygous mutation in the CYBB gene. They also presented a wide range of clinical manifestations most frequently bacterial and fungal infections of the respiratory tract, skin, and lymph nodes. Thirty percent of the Latin American CGD patients presented adverse reactions to BCG, indicating that this vaccine should be avoided in these patients.

Ex vivo assessment of cellular immune function - applications in patient care and clinical studies

Cellular ex vivo assays have a broad range of applications in patient care and clinical studies, especially when they are standardized and highly sensitive. As compared to analyses by molecular genetics such as the single nucleotide polymorphism (SNP) testing, they are usually more global. These assays partly mimic the in vivo situation, relying on a complex interaction of various immune cells. For example, they can be used to determine modulation of alloresponses by treatment or underlying disease, diagnose and quantify primary and secondary cellular immunodeficiency, follow-up vaccination responses, measure adoptive transfer of virus-specific immunity via hematopoietic stem cell or liver transplantation, assess allergy, antimicrobial immunity and also rare effector/memory cells directed against tumor antigens. This review will first shortly describe various cellular in vitro methods and then present applications, summarizing some own studies performed within the last 18 years.

Identification of a Novel Mutation in the CYBB Gene, p.Asp378Gly, in a Patient With X-linked Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is a rare immunodeficiency disease, which is characterized by the lack of a functional nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in phagocytes. The disease presents leukocytosis, anemia, hypergammaglobulinemia, and granuloma formation of the skin, lung, or lymph nodes. The mutation of the CYBB gene encoding gp91phox, located on chromosome Xp21.1 is one of the causes of CGD. We report a patient with X-linked CGD who carried a novel mutation, a c.1133A>G (paAsp378Gly) missense mutation, in the CYBB gene.

Improvement of a rapid screening test for chronic granulomatous disease

Diagnosis of CGD is made by demonstrating absent or markedly reduced oxidase activity in stimulated neutrophils. The screening test proposed is based upon the naked eye evaluation of the reduction of NBT on a solid surface. It seems to be a useful tool for rapid and inexpensive detection of CGD patients, especially for large-scale screening purposes. The test was carried out on forty-five subjects: two males affected by CGD, three female carriers and forty healthy donors. The test confirmed the results obtained with flow cytometric and NBT assays.

Clinical, functional, and genetic characterization of chronic granulomatous disease in 89 Turkish patients

BACKGROUND

Chronic granulomatous disease (CGD) is a rare primary immunodeficiency disorder of phagocytes resulting in impaired killing of bacteria and fungi. A mutation in one of the 4 genes encoding the components p22(phox), p47(phox), p67(phox), and p40(phox) of the leukocyte nicotinamide dinucleotide phosphate reduced (NADPH) oxidase leads to autosomal recessive (AR) CGD. A mutation in the CYBB gene encoding gp91(phox) leads to X-linked recessive CGD.

OBJECTIVE

The aim of this study is to show the correlation between clinical, functional, and genetic data of patients with CGD from Turkey.

METHODS

We report here the results of 89 patients with CGD from 73 Turkish families in a multicenter study.

RESULTS

Most of the families (55%) have an AR genotype, and 38% have an X-linked genotype; patients from 5 families with a suspected AR genotype (7%) were not fully characterized. We compared patients with CGD according to the severity of NADPH oxidase deficiency of neutrophils. Patients with A22(0), A67(0) or X91(0) phenotypes with a stimulation index of 1.5 or less have early clinical presentation and younger age at diagnosis (mean, 3.2 years). However, in p47(phox)-deficient cases and in 5 other AR cases with high residual oxidase activity (stimulation index ≥ 3), later and less severe clinical presentation and older age at diagnosis (mean, 7.1 years) were found. Pulmonary involvement was the most common clinical feature, followed by lymphadenitis and abscesses.

CONCLUSION

Later and less severe clinical presentation and older age at diagnosis are related to the residual NADPH oxidase activity of neutrophils and not to the mode of inheritance. CGD caused by A22(0) and A67(0) subtypes manifests as severe as the X91(0) subtype.

Rapid determination of chimerism status using dihydrorhodamine assay in a patient with X-linked chronic granulomatous disease following hematopoietic stem cell transplantation

Chronic granulomatous disease (CGD) is a rare genetic disease, which is caused by defects in the NADPH oxidase complex (gp91^phox, p22^phox, p40^phox, p47^phox, and p67^phox) of phagocytes. This defect results in impaired production of superoxide anions and other reactive oxygen species (ROS), which are necessary for killing bacterial and fungal microorganisms and leads to recurrent, life-threatening bacterial and fungal infections and granulomatous inflammation. The dihydrorhodamine (DHR) flow cytometry assay is a useful diagnostic tool for CGD that can detect absent or reduced NADPH oxidase activity in stimulated phagocytes. We report a patient with X-linked CGD carrying a novel mutation of the CYBB gene whose chimerism status following hematopoietic stem cell transplantation (HSCT) has been rapidly determined using the DHR assay. The level of DHR activity correlates well with short tandem repeat PCR analysis. Considering the advantages of this simple, rapid, and cost-effective procedure, serial measurement of DHR assay would facilitate the rapid determination of a patient's engraftment status, as a supplementary monitoring tool of chimerism status following HSCT.

ROS production in phagocytes: why, when, and where?

In the phagocytosis field, ROS production by the phagocyte NOX has been associated with pathogen killing for the last 50 years. Since the discovery of nonphagocyte NOX, numerous other roles for ROS production have been identified. Oxidative stress and ROS-mediated signaling have received much attention in recent years. Much lower concentrations of ROS may be required for signaling compared with microbial killing. Based on the discoveries in nonphagocytic cells, it became logical to look for ROS functions distinct from pathogen killing, even in phagocytes. ROS are now linked to various forms of cell death, to chemotaxis, and to numerous modifications of cellular processes, including the NOX itself. ROS functions are clearly concentration-dependent over a wide range of concentrations. How much is required for which function? Which species are required for how much time? Is ROS signaling only a side effect of bactericidal ROS production? One major obstacle to answer these questions is the difficulty of reliable quantitative ROS detection. Signal transduction often takes place on a subcellular scale over periods of seconds or minutes, so the detection methods need to provide appropriate time and space resolution. We present examples of local ROS production, decreased degradation, signaling events, and potentially ROS-sensitive functions. We attempt to illustrate the current limitations for quantitative spatiotemporal ROS detection and point out directions for ongoing development. Probes for localized ROS detection and for combined detection of ROS, together with protein localization or other cellular parameters, are constantly improved.

Reactive oxygen species alteration of immune cells in local residents at an electronic waste recycling site in northern China

The health effects of exposure to pollutants from electronic waste (e-waste) pose an important issue. In this study, we explored the association between oxidative stress and blood levels of e-waste-related pollutants. Blood samples were collected from individuals living in the proximity of an e-waste recycling site located in northern China, and pollutants, as well as reactive oxygen species (ROS), were measured in comparison to a reference population. The geometric mean concentrations of PCBs, dechlorane plus, and 2,2',4,4',5,5'-hexabromobiphenyl in plasma from the exposure group were 60.4, 9.0, and 0.55 ng g(-1) lipid, respectively, which were 2.2, 3.2, and 2.2 times higher than the corresponding measurement in the reference group. Correspondingly, ROS levels in white blood cells, including in neutrophil granulocytes, from the exposure group were significantly higher than in those from the reference group, suggesting potential ROS related health effects for residents at the e-waste site. In contrast, fewer ROS were generated in the respiratory burst of neutrophil granulocytes for the exposure group, indicating a depressed innate immune function for the individuals living at the e-waste site. These findings suggest a potential linkage between exposure to pollutants from e-waste recycling and both elevated oxidative stress and altered immune function.

Chemokine receptor Ccr1 drives neutrophil-mediated kidney immunopathology and mortality in invasive candidiasis

Invasive candidiasis is the 4^th leading cause of nosocomial bloodstream infection in the US with mortality that exceeds 40% despite administration of antifungal therapy; neutropenia is a major risk factor for poor outcome after invasive candidiasis. In a fatal mouse model of invasive candidiasis that mimics human bloodstream-derived invasive candidiasis, the most highly infected organ is the kidney and neutrophils are the major cellular mediators of host defense; however, factors regulating neutrophil recruitment have not been previously defined. Here we show that mice lacking chemokine receptor Ccr1, which is widely expressed on leukocytes, had selectively impaired accumulation of neutrophils in the kidney limited to the late phase of the time course of the model; surprisingly, this was associated with improved renal function and survival without affecting tissue fungal burden. Consistent with this, neutrophils from wild-type mice in blood and kidney switched from Ccr1^lo to Ccr1^high at late time-points post-infection, when Ccr1 ligands were produced at high levels in the kidney and were chemotactic for kidney neutrophils ex vivo. Further, when a 1∶1 mixture of Ccr1^+/+ and Ccr1^−/− donor neutrophils was adoptively transferred intravenously into Candida-infected Ccr1^+/+ recipient mice, neutrophil trafficking into the kidney was significantly skewed toward Ccr1^+/+ cells. Thus, neutrophil Ccr1 amplifies late renal immunopathology and increases mortality in invasive candidiasis by mediating excessive recruitment of neutrophils from the blood to the target organ.

Invasive infection by the yeast Candida represents a significant cause of morbidity and mortality in patients in the intensive care unit. Neutrophils, which are recruited to sites of Candida infection by chemokines and their receptors, are important immune cells in host defense against invasive candidiasis. Consistent with that, lack of neutrophils is a well-established risk factor for adverse outcome after infection. In this study, we performed a broad survey of the chemokine system in a mouse model of invasive candidiasis with an aim to determine factors that regulate neutrophil trafficking to sites of infection. We used that survey to identify Ccr1 as a mediator of mortality in the model via excessive recruitment of neutrophils from the blood to the kidney that results in kidney tissue injury. Strikingly, the effect of Ccr1 on neutrophil accumulation in the kidney was not seen until the late phase of the infection, when the receptor was up-regulated on the neutrophil surface. Together these data demonstrate that neutrophils, besides their recognized protective roles in antifungal host defense, may also exert detrimental effects by causing uncontrolled tissue damage, and identify Ccr1 as a mediator of neutrophil tissue injury in a mouse model of invasive candidiasis.

The CXCR4 antagonist plerixafor corrects panleukopenia in patients with WHIM syndrome

WHIM syndrome is a rare congenital immunodeficiency disorder characterized by warts, hypogammaglobulinemia, infections, and myelokathexis (neutropenia because of impaired egress from the BM); most patients also have severe panleukopenia. Because WHIM syndrome is caused by mutations in the chemokine receptor CXCR4 that result in increased agonist-dependent signaling, we hypothesized that the CXCR4 antagonist plerixafor (Mozobil [Genyzme Corporation], AMD3100), might be an effective treatment. To test this, we enrolled 3 unrelated adult patients with the most common WHIM mutation, CXCR4(R334X), in a phase 1 dose-escalation study. Plerixafor increased absolute lymphocyte, monocyte, and neutrophil counts in blood to normal without significant side effects in all 3 patients. Peak responses occurred at 3-12 hours after injection and waned by 24 hours after injection which tracked the drug's pharmacokinetics. All 3 cell types increased in a dose-dependent manner with the rank order of responsiveness absolute lymphocyte > monocyte > neutrophil. These data provide the first pharmacologic evidence that panleukopenia in WHIM syndrome is caused by CXCL12-CXCR4 signaling-dependent leukocyte sequestration, and support continued study of plerixafor as mechanism-based therapy in this disease. This study is registered at http://www.clinicaltrials.gov as NCT00967785.

Inheritance pattern and clinical aspects of 93 Iranian patients with chronic granulomatous disease

BACKGROUND

Chronic granulomatous disease (CGD) is a rare immunodeficiency due to a genetic defect in one of the NADPH-oxidase components. We studied CGD inheritance forms (autosomal recessive (AR) or X-linked (XL)) and AR-CGD subtypes in Iran.

METHODS

Clinical and functional investigations were conducted in 93 Iranian CGD patients from 75 families.

RESULTS

Most of the patients were AR-CGD (87.1%). This was related to consanguineous marriages (p = 0.001). The age of onset of symptoms and diagnosis were lower in XL-CGD compared with AR-CGD (p < 0.0001 for both). Among AR-CGD patients, p47phox defect was the predominant subtype (55.5%). The most common clinical features in patients were lymphadenopathy (65.6%) and pulmonary involvement (57%). XL-CGD patients were affected more frequently with severe infectious manifestations.

CONCLUSIONS

Although XL-CGD is the most common type of the disease worldwide, only 12 patients (12.9%) were XL-CGD in our study. The relatively high frequency of AR-CGD is probable due to widely common consanguineous marriages in Iran.

Distribution, clinical features and treatment in Taiwanese patients with symptomatic primary immunodeficiency diseases (PIDs) in a nationwide population-based study during 1985-2010

Primary immunodeficiency diseases (PIDs) are a group of rare diseases with wide geographic and ethnic variations in incidence, prevalence, and distribution patterns. The aim of this study was to examine the distribution pattern and clinical spectrum of PIDs in Taiwan at a national referral institute. From 1985 to 2010, 215 patients from 183 families were diagnosed and grouped according to the updated classification of PIDs. Eighty-one (37.7%) patients had "other well-defined immunodeficiency syndromes", followed by "predominantly antibody deficiencies" (54 patients; 25.1%), "T- and B-cell immunodeficiencies" (34; 15.8%), "congenital defects of phagocytes" (25; 20.2%), "complement deficiencies" (15; 7.0%), and "disease in immune dysregulation" (5; 2.3%). The last category included two patients with Chediak-Higashi syndrome, and one each with familial hemophagocytosis, IPEX, and hypogammaglobulinemia and albinism. One female had cold-induced auto-inflammatory disease. There were no cases of "defects in innate immunity". Pseudomonas and Streptococcus pneumoniae were the two most identified microorganisms in septicemia (42.7%; 44/103 episodes). Stem cell transplantation was successful in 13 of 22 patients, while 34 patients (15.8%) died. Molecular defects were identified in 109 individuals (from 90 families). There were relatively fewer cases of "predominantly antibody deficiencies" due to there being only a few patients with adult-onset PIDs, implying certainty bias rather than ethnic variation. Awareness of under-diagnosis among physicians rather than pediatricians is vital for timely diagnosis and consequently adequate treatment.

Molecular- and flow cytometry-based diagnosis of primary immunodeficiency disorders

Primary immunodeficiencies are an expanding group of genetic disorders resulting in recurrent and/or severe infections, autoimmunity, or autoinflammation. The laboratory plays a critical role in the diagnosis of these conditions given their frequently overlapping signs and symptoms. We discuss here advances in flow cytometry and molecular techniques applied to the study of primary immunodeficiencies.

Residual NADPH oxidase and survival in chronic granulomatous disease

BACKGROUND

Failure to generate phagocyte-derived superoxide and related reactive oxygen intermediates (ROIs) is the major defect in chronic granulomatous disease, causing recurrent infections and granulomatous complications. Chronic granulomatous disease is caused by missense, nonsense, frameshift, splice, or deletion mutations in the genes for p22(phox), p40(phox), p47(phox), p67(phox) (autosomal chronic granulomatous disease), or gp91(phox) (X-linked chronic granulomatous disease), which result in variable production of neutrophil-derived ROIs. We hypothesized that residual ROI production might be linked to survival in patients with chronic granulomatous disease.

METHODS

We assessed the risks of illness and death among 287 patients with chronic granulomatous disease from 244 kindreds. Residual ROI production was measured with the use of superoxide-dependent ferricytochrome c reduction and flow cytometry with dihydrorhodamine oxidation assays. Expression of NADPH oxidase component protein was detected by means of immunoblotting, and the affected genes were sequenced to identify causal mutations.

RESULTS

Survival of patients with chronic granulomatous disease was strongly associated with residual ROI production as a continuous variable, independently of the specific gene affected. Patients with mutations in p47(phox) and most missense mutations in gp91(phox) (with the exception of missense mutations in the nucleotide-binding and heme-binding domains) had more residual ROI production than patients with nonsense, frameshift, splice, or deletion mutations in gp91(phox). After adolescence, mortality curves diverged according to the extent of residual ROI production.

CONCLUSIONS

Patients with chronic granulomatous disease and modest residual production of ROI have significantly less severe illness and a greater likelihood of long-term survival than patients with little residual ROI production. The production of residual ROI is predicted by the specific NADPH oxidase mutation, regardless of the specific gene affected, and it is a predictor of survival in patients with chronic granulomatous disease. (Funded by the National Institutes of Health.).

Severe congenital neutropenia resulting from G6PC3 deficiency with increased neutrophil CXCR4 expression and myelokathexis

Mutations in more than 15 genes are now known to cause severe congenital neutropenia (SCN); however, the pathologic mechanisms of most genetic defects are not fully defined. Deficiency of G6PC3, a glucose-6-phosphatase, causes a rare multisystem syndrome with SCN first described in 2009. We identified a family with 2 children with homozygous G6PC3 G260R mutations, a loss of enzymatic function, and typical syndrome features with the exception that their bone marrow biopsy pathology revealed abundant neutrophils consistent with myelokathexis. This pathologic finding is a hallmark of another type of SCN, WHIM syndrome, which is caused by gain-of-function mutations in CXCR4, a chemokine receptor and known neutrophil bone marrow retention factor. We found markedly increased CXCR4 expression on neutrophils from both our G6PC3-deficient patients and G6pc3(-/-) mice. In both patients, granulocyte colony-stimulating factor treatment normalized CXCR4 expression and neutrophil counts. In G6pc3(-/-) mice, the specific CXCR4 antagonist AMD3100 rapidly reversed neutropenia. Thus, myelokathexis associated with abnormally high neutrophil CXCR4 expression may contribute to neutropenia in G6PC3 deficiency and responds well to granulocyte colony-stimulating factor.

Laboratory evaluation of primary immunodeficiencies

Primary immunodeficiencies are congenital disorders caused by defects in different elements of the immune system. Affected patients usually present clinically with recurrent infections, severe infections, or both, as well as autoimmune phenomena that are associated with many of these disorders. Early diagnosis is essential for referral to specialized care centers and the prompt initiation of appropriate therapy. In this article the authors describe a general approach for the investigation of the most common primary immunodeficiencies, outlining the typical clinical symptoms and most appropriate laboratory investigations.

Family clusters of variant X-linked chronic granulomatous disease

Chronic granulomatous disease (CGD) is a rare inherited immunodeficiency disorder. The clinical presentation is varied depending on the degree of involvement of the NADPH oxidase system responsible for the oxidative burst of neutrophils. We present 3 cases of variant X-linked CGD in an effort to introduce the disease and highlight the importance and limitations of CGD screening. The variant X-linked form of CGD results in a less severe phenotype and frequently presents later in life. Variant X-linked CGD is difficult to diagnose, but is becoming more readily recognized based on improved testing methods. A high index of suspicion in the setting of unusual infections such as Burkholderia cepacia pneumonia is essential to make the diagnosis. Family screening can lead to early intervention, prophylaxis, and appropriate genetic counseling.

Molecular diagnosis of X-linked chronic granulomatous disease in Iran

Chronic granulomatous disease (CGD) is an inherited disorder of pathogen killing by phagocytic leukocytes caused by mutations in NADPH oxidase subunits. Patients with CGD have life-threatening bacterial and fungal infections. Children's Medical Center at Tehran University is the referral center for immunodeficiency in Iran. During 2 years of study, 11 non-consanguineous families with clinically diagnosed CGD were referred to this center. In functional assays performed on neutrophils from affected children and their mothers; no activity or strongly decreased oxidase activity was detected in the patients' cells. In oxidase tests that scored this activity on a per-cell basis, a mosaic pattern was detected in the neutrophils from all 11 mothers. Western blot analysis revealed an X91 degrees phenotype in all patients. Mutation screening in the CYBB gene encoding gp91(phox) by SSCP analysis followed by sequencing showed nine different mutations, including two novel mutations. The present survey is the first study aimed to analyze the clinical features and the molecular diagnosis of X-CGD in Iranian patients.

Characterization of six novel mutations in CYBA: the gene causing autosomal recessive chronic granulomatous disease

One of the rarest forms of chronic granulomatous disease (CGD) is caused by mutations in CYBA, which encodes the p22-phox subunit of the phagocyte NADPH oxidase, leading to defective intracellular killing. This study investigated eight patients (six males and two females) from seven consanguineous, unrelated families with clinical CGD, positive family history and p22-phox deficiency. Mutation analysis of CYBA showed six different novel mutations: deletion of exons 3, 4 and 5; a missense mutation in exon 6 (c.373G>A); a splice site mutation in intron 5 (c.369+1G>A); a frameshift in exon 6 (c.385delGAGC); a frameshift in exon 3 (c.174delG); and a frameshift in exon 4 (c.223delC).

Genetic immunodeficiency diseases

The approach to the patient with genetic immunodeficiency is multidisciplinary, and requires close interaction between the primary care physician, immunologist, and other specialists. Dermatologists may play a key role in both the diagnosis of immunodeficiency based on recurrent infection or specific cutaneous abnormalities and in the management of cutaneous complications. The availability of bone marrow and stem cell transplantation has been life-saving for many affected children. The underlying genetic basis is now known for most forms of immunodeficiency, which has facilitated confirmation of patient diagnosis and prenatal diagnosis. Gene therapy has already been initiated for severe combined immunodeficiency, and will certainly play a growing role in therapy of this group of disorders in the future.