Comprehensive comparison between 222 CTLA-4 haploinsufficiency and 212 LRBA deficiency patients: a systematic review

Comprehensive insights into pathogenesis, diagnosis, treatment, and prognosis in adult autoimmune enteropathy

Autoimmune enteropathy (AIE) constitutes a diverse array of disorders characterized by immune dysregulation and gastrointestinal manifestations, chiefly chronic diarrhea. Due to the small number of reported cohorts, the current knowledge and understanding of adult-onset AIE is rare compared with pediatric or syndromic AIE. Pathogenesis might involve genetic predisposition, aberrant immune homeostasis, comorbidities of autoimmune diseases and environmental trigger. Diagnosis relies on a comprehensive assessment encompassing clinical evaluation, laboratory tests, endoscopic findings and histopathological features, yet distinguishing AIE from other disorders with similar presentations poses diagnostic challenges. Treatment strategies predominantly center on immunosuppressive therapies, exhibiting varied efficacy among individuals. Supportive treatment and prevention and management of complications are also important for prognosis. The prospectives of future researches need to explore the genetic and immunological mechanism, the diagnostic modalities and the treatment strategies to improve patient outcomes.

Abatacept Induces Long-Term Reconstitution of the B-Cell Niche in a Patient With CTLA-4 Haploinsufficiency: A Case Report

OBJECTIVES

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) haploinsufficiency is a rare genetic condition characterized by development of immune cytopenia, hypogammaglobulinemia, and/or lymphoproliferative disorder, as well as multiple autoimmunity. Treatment with abatacept was shown to alleviate autoimmune conditions, yet its long-lasting impact on bone marrow function remains undetermined.

METHODS

We here present the case of a now 39-year-old woman with CTLA-4 haploinsufficiency with predominant CNS affection, yet multiorgan autoimmunity and lymphopenia. We conducted single-cell RNA sequencing (scRNA-seq) of peripheral mononuclear blood cells before and after abatacept induction.

RESULTS

After several high-efficacy immunosuppressive treatments with little-to-no response, she started abatacept in 2017 and experienced ongoing remission including resolution of pre-existing immune cytopenia and hypogammaglobulinemia. Using scRNA-seq, we were able to demonstrate reconstitution of peripheral B cells accompanied by reduction of CD8+ T cells. CD4+ and CD8+ T cells were characterized by downregulation of pathways involved in activation of innate immune cells.

DISCUSSION

Our findings demonstrate long-lasting resolution of lymphopenia after abatacept treatment in CTLA-4 haploinsufficiency despite severity and duration of symptoms. Thus, abatacept should be considered throughout before stem cell transplantation also in CTLA-4 haploinsufficiency with severe symptoms.

CLASSIFICATION OF EVIDENCE

As a single report without controls, this report provides class IV evidence that abatacept might revert lymphopenia in patients with CTLA-4 haploinsufficiency.

Expanding the diagnostic toolbox for complex genetic immune disorders

Laboratory-based immunology evaluation is essential to the diagnostic workup of patients with complex immune disorders, and is as essential, if not more so, depending on the context, as genetic testing, because it enables identification of aberrant pathways amenable to therapeutic intervention and clarifies variants of uncertain significance. There have been considerable advances in techniques and instrumentation in the clinical laboratory in the past 2 decades, although there are still "miles to go." One of the goals of the clinical laboratory is to ensure advanced diagnostic testing is widely accessible to physicians and thus patients, through reference laboratories, particularly in the context of academic medical centers. This ensures a greater likelihood of translating research discoveries into the diagnostic laboratory, on the basis of patient care needs rather than a sole emphasis on commercial utility. However, these advances are under threat from burdensome regulatory oversight that can compromise, at best, and curtail, at worst, the ability to rapidly diagnose rare immune disorders and ensure delivery of precision medicine. This review discusses the clinical utility of diagnostic immunology tools, beyond cellular immunophenotyping of lymphocyte subsets, which can be used in conjunction with clinical and other laboratory data for diagnosis as well as monitoring of therapeutic response in patients with genetic immunologic diseases.

The effect of HLA genotype on disease onset and severity in CTLA-4 insufficiency

Introduction

Human Cytotoxic-T-lymphocyte-antigen-4 (CTLA-4) insufficiency caused by heterozygous germline mutations in CTLA4 is a complex immune dysregulation and immunodeficiency syndrome presenting with reduced penetrance and variable disease expressivity, suggesting the presence of disease modifiers that trigger the disease onset and severity. Various genetic and non-genetic potential triggers have been analyzed in CTLA-4 insufficiency cohorts, however, none of them have revealed a clear association to the disease. Multiple HLA haplotypes have been positively or negatively associated with various autoimmune diseases and inborn errors of immunity (IEI) due to the relevance of MHC in the strength of the T cell responses.

Methods

In this exploratory study, we investigated the association of disease onset, severity and clinical manifestations of CTLA-4 insufficiency with specific HLA class I (A, B and C) and class II (DRB1 and DQB1) alleles in forty-three individuals harboring heterozygous mutations in CTLA4. Twenty-six out of the 43 recruited individuals presented moderate or severe clinical symptoms whereas 17 were completely healthy. HLA frequency analysis, odds ratio analysis and genetic linkage analysis were used.

Results

The principal statistical analyses showed no positive association between the HLA genotypes analyzed with the disease onset or the disease severity. We found potential risk associations of HLA-DQB1*05:01 and HLA-DRB1*01:02 with respiratory tract involvement and HLA-C*05:01 with affection of the neurological system in the CTLA-4-insufficient patients. Additionally, we found a potential protective association of HLA-DRB1*01:01 with gastrointestinal symptoms.

Discussion

Even though, our findings suggest that HLA-A, -B, -C, DRB1, and DQB1 do not contribute to the onset or severity of disease in CTLA-4 insufficiency, certain HLA-alleles may influence the manifestation of specific symptoms. We advocate for further investigation of specific class I and class II HLA alleles as potential disease modifiers in larger clinical cohorts of CTLA-4 insufficiency.

Hematopoietic stem cell transplantation for CTLA-4 insufficiency across Europe: A European Society for Blood and Marrow Transplantation Inborn Errors Working Party study

BACKGROUND

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) insufficiency causes a primary immune regulatory disorder characterized by lymphoproliferation, dysgammaglobulinemia, and multiorgan autoimmunity including cytopenias and colitis.

OBJECTIVE

We examined the outcome of hematopoietic stem cell transplantation (HSCT) for CTLA-4 insufficiency and study the impact of pre-HSCT CTLA-4 fusion protein (CTLA-4-Ig) therapy and pre-HSCT immune dysregulation on survival and immunologic outcome.

METHODS

This was a retrospective study of HSCT for CTLA-4 insufficiency and 2q33.2-3 deletion from the European Society for Blood and Marrow Transplantation Inborn Errors Working Party. Primary end points were overall survival (OS) and disease- and chronic graft-versus-host disease-free survival (DFS). Secondary end point was immunologic outcome assessed by immune dysregulation disease activity (IDDA) score.

RESULTS

Forty patients were included over a 25-year period. Before HSCT, 60% received CTLA-4-Ig, and median (range) IDDA score was 23.3 (3.9-84.0). Median (range) age at HSCT was 14.2 (1.3-56.0) years. Patients received peripheral blood stem cell (58%) or marrow (43%) from a matched unrelated donor (75%), mismatched unrelated donor (12.5%), or matched family donor (12.5%). Median (range) follow-up was 3 (0.6-15) years, and 3-year OS was 76.7% (58-87%) and DFS was 74.4% (54.9-86.0%). At latest follow-up, disease of 28 of 30 surviving patients was in disease-free remission with median IDDA reduction of 16. Probability of OS and DFS was greater in patients with lower disease activity before HSCT (IDDA < 23, P = .002 and P = .006, respectively). CTLA-4-Ig receipt did not influence OS or DFS. Cause of death was transplant related in 7 of 8 patients.

CONCLUSION

HSCT is an effective therapy to prevent ongoing disease progression and morbidity, with improving survival rates over time and in patients with lower pre-HSCT disease activity.

Transplantation for immune dysregulatory disorders: current themes and future expectations

PURPOSE OF REVIEW

Primary immune regulatory disorders (PIRDs) are an increasing indication for hematopoietic stem cell transplant (HCT) in pediatric patients. Here, we provide an updated overview of HCT for PIRDs, and discuss future avenues for improvement in outcomes.

RECENT FINDINGS

There are now more than 50 described monogenic PIRDs, which impact all aspects of immune tolerance, regulation, and suppression. Disease characteristics are highly variable, and HCT remains the only option for cure. We review advances in targeted therapies for individual PIRDs, which have significantly improved outcomes and the ability to safely bridge to transplant. Additionally, advances in GVHD prevention, graft manipulation, personalized conditioning regimens, and supportive care have all increased survival after HCT. The high inflammatory state increases the risk of nonengraftment, rejection, and autologous reconstitution. Therapy to reduce the inflammatory state may further improve outcomes. In addition, although younger patients with fewer comorbidities have better outcomes, the clinical courses of these diseases may be extremely variable thereby complicating the decision to proceed to HCT.

SUMMARY

HCT for PIRDs is a growing consideration in cell therapy. Yet, there remain significant gaps in our understanding of which patients this curative therapy could benefit the most. Here, we review the current data supporting HCT for PIRDs as well as areas for future improvement.

Deletion upstream of MAB21L2 highlights the importance of evolutionarily conserved non-coding sequences for eye development

Anophthalmia, microphthalmia and coloboma (AMC) comprise a spectrum of developmental eye disorders, accounting for approximately 20% of childhood visual impairment. While non-coding regulatory sequences are increasingly recognised as contributing to disease burden, characterising their impact on gene function and phenotype remains challenging. Furthermore, little is known of the nature and extent of their contribution to AMC phenotypes. We report two families with variants in or near MAB21L2, a gene where genetic variants are known to cause AMC in humans and animal models. The first proband, presenting with microphthalmia and coloboma, has a likely pathogenic missense variant (c.338 G > C; p.[Trp113Ser]), segregating within the family. The second individual, presenting with microphthalmia, carries an ~ 113.5 kb homozygous deletion 19.38 kb upstream of MAB21L2. Modelling of the deletion results in transient small lens and coloboma as well as midbrain anomalies in zebrafish, and microphthalmia and coloboma in Xenopus tropicalis. Using conservation analysis, we identify 15 non-coding conserved elements (CEs) within the deleted region, while ChIP-seq data from mouse embryonic stem cells demonstrates that two of these (CE13 and 14) bind Otx2, a protein with an established role in eye development. Targeted disruption of CE14 in Xenopus tropicalis recapitulates an ocular coloboma phenotype, supporting its role in eye development. Together, our data provides insights into regulatory mechanisms underlying eye development and highlights the importance of non-coding sequences as a source of genetic diagnoses in AMC.

Association of paediatric autoimmune cytopenia and inflammatory bowel disease suggests a common genetic origin

The association of autoimmune cytopenia (AIC) and inflammatory bowel disease (IBD) has been reported in small series, but the incidence of and risk factors for IBD in children with AIC are not known. One thousand six hundred nine children with chronic immune thrombocytopenic purpura, autoimmune haemolytic anaemia or Evans syndrome from the prospective OBS'CEREVANCE cohort are included in this study. Overall, 15 children were diagnosed with IBD, including 14 who developed IBD after AIC diagnosis (median delay: 21 months). The only risk factor for IBD development is age at AIC over 10 years. Out of 10 children genetically tested, germline variants associated with autoimmune disorders were identified in three (CTLA4: two, DOCK11: one). In children and adolescents monitored for AIC or past history of AIC, especially children over 10 years, gastro-intestinal (GI) symptoms (recurrent abdominal pains, GI bleeding, chronic diarrhoea, weight loss) should suggest IBD and deserve specific work-up and genetic studies. Identification of a causal germline variant will allow targeted therapy.

Sarcoidosis versus Granulomatous and Lymphocytic Interstitial Lung Disease in Common Variable Immunodeficiency: A Comparative Review

Sarcoidosis and Granulomatous and Lymphocytic Interstitial Lung Diseases (GLILD) are two rare entities primarily characterised by the development of Interstitial Lung Disease (ILD) in the context of systemic immune dysregulation. These two conditions partially share the immunological background and pathologic findings, with granuloma as the main common feature. In this narrative review, we performed a careful comparison between sarcoidosis and GLILD, with an overview of their main similarities and differences, starting from a clinical perspective and ending with a deeper look at the immunopathogenesis and possible target therapies. Sarcoidosis occurs in immunocompetent individuals, whereas GLILD occurs in patients affected by common variable immunodeficiency (CVID). Moreover, peculiar extrapulmonary manifestations and radiological and histological features may help distinguish the two diseases. Despite that, common pathogenetic pathways have been suggested and both these disorders can cause progressive impairment of lung function and variable systemic granulomatous and non-granulomatous complications, leading to significant morbidity, reduced quality of life, and survival. Due to the rarity of these conditions and the extreme clinical variability, there are still many open questions concerning their pathogenesis, natural history, and optimal management. However, if studied in parallel, these two entities might benefit from each other, leading to a better understanding of their pathogenesis and to more tailored treatment approaches.

NGS data analysis for molecular diagnosis of Inborn Errors of Immunity

Inborn errors of immunity (IEI) encompass a group of disorders with a strong genetic component. Prompt and accurate diagnosis of these disorders is essential for effective clinical management. Next-generation sequencing (NGS) has significantly enhanced the diagnostic process by offering a comprehensive and scalable approach for identifying genomic variations causal for these disorders. Nevertheless, the bioinformatics analysis of NGS data poses several challenges. In this review, we explore these challenges and share our insights on addressing them, aiming to improve the overall diagnostic yield.

Analysis of LRBA pathogenic variants and the association with functional protein domains and clinical presentation

LRBA is a cytoplasmic protein that is ubiquitously distributed. Almost all LRBA domains have a scaffolding function. In 2012, it was reported that homozygous variants in LRBA are associated with early-onset hypogammaglobulinemia. Since its discovery, more than 100 pathogenic variants have been reported. This review focuses on the variants reported in LRBA and their possible associations with clinical phenotypes. In this work LRBA deficiency cases reported more than 11 years ago have been revised. A database was constructed to analyze the type of variants, age at onset, clinical diagnosis, infections, autoimmune diseases, and cellular and immunoglobulin levels. The review of cases from 2012 to 2023 showed that LRBA deficiency was commonly diagnosed in patients with a clinical diagnosis of Common Variable Immunodeficiency, followed by enteropathy, neonatal diabetes mellitus, ALPS, and X-linked-like syndrome. Most cases show early onset of presentation at <6 years of age. Most cases lack protein expression, whereas hypogammaglobulinemia is observed in half of the cases, and IgG and IgA levels are isotypes reported at low levels. Patients with elevated IgG levels exhibited more than one autoimmune manifestation. Patients carrying pathogenic variants leading to a premature stop codon show a severe phenotype as they have an earlier onset of disease presentation, severe autoimmune manifestations, premature death, and low B cells and regulatory T cell levels. Missense variants were more common in patients with low IgG levels and cytopenia. This work lead to the conclusion that the type of variant in LRBA has association with disease severity, which leads to a premature stop codon being the ones that correlates with severe disease.

LRBA, a BEACH protein mutated in human immune deficiency, is widely expressed in epithelia, exocrine and endocrine glands, and neurons

Mutations in LRBA, a BEACH domain protein, cause severe immune deficiency in humans. LRBA is expressed in many tissues and organs according to biochemical analysis, but little is known about its cellular and subcellular localization, and its deficiency phenotype outside the immune system. By LacZ histochemistry of Lrba gene-trap mice, we performed a comprehensive survey of LRBA expression in numerous tissues, detecting it in many if not all epithelia, in exocrine and endocrine cells, and in subpopulations of neurons. Immunofluorescence microscopy of the exocrine and endocrine pancreas, salivary glands, and intestinal segments, confirmed these patterns of cellular expression and provided information on the subcellular localizations of the LRBA protein. Immuno-electron microscopy demonstrated that in neurons and endocrine cells, which co-express LRBA and its closest relative, neurobeachin, both proteins display partial association with endomembranes in complementary, rather than overlapping, subcellular distributions. Prominent manifestations of human LRBA deficiency, such as inflammatory bowel disease or endocrinopathies, are believed to be primarily due to immune dysregulation. However, as essentially all affected tissues also express LRBA, it is possible that LRBA deficiency enhances their vulnerability and contributes to the pathogenesis.

Clinical and experimental treatment of primary humoral immunodeficiencies

Selective IgA deficiency (sIgAD), common variable immunodeficiency (CVID), and transient hypogammaglobulinemia of infancy (THI) are the most frequent forms of primary antibody deficiencies. Difficulties in initial diagnosis, especially in the early childhood, the familiar occurrence of these diseases, as well as the possibility of progression to each other suggest common cellular and molecular patomechanism and a similar genetic background. In this review, we discuss both similarities and differences of these three humoral immunodeficiencies, focusing on current and novel therapeutic approaches. We summarize immunoglobulin substitution, antibiotic prophylaxis, treatment of autoimmune diseases, and other common complications, i.e. cytopenias, gastrointestinal complications, and granulomatous disease. We discuss novel therapeutic approaches such as allogenic stem cell transplantation and therapies targeting-specific proteins, dependent on the patient's genetic defect. The diversity of possible therapeutics models results from a great heterogeneity of the disease variants, implying the need of personalized medicine approach as a future of primary humoral immunodeficiencies treatment.

Clinical updates in inborn errors of immunity: a focus on the noninfectious clinical manifestations

PURPOSE OF REVIEW

In the last 5 years, several new inborn errors of immunity (IEI) have been described, especially in the areas of immune dysregulation and autoinflammation. As a result, the clinical presentation of IEIs has broadened. We review the heterogeneous presentation of IEIs and detail several of the recently described IEIs with a focus on the noninfectious manifestations commonly seen.

RECENT FINDINGS

IEIs may present with early onset and/or multiple autoimmune manifestations, increased risk for malignancy, lymphoproliferation, severe atopy, autoinflammation and/or hyperinflammation. Because of this, patients can present to a wide array of providers ranging from primary care to various pediatric subspecialists. The International Union of Immunological Societies (IUIS) expert committee has created a phenotypic classification of IEIs in order to help clinicians narrow their evaluation based on the laboratory and clinical findings.

SUMMARY

Both primary care pediatricians and pediatric subspecialists need to be aware of the common clinical features associated with IEI and recognize when to refer to allergy-immunology for further evaluation. Early diagnosis can lead to earlier treatment initiation and improve clinical outcomes for our patients.

Tipping the balance in autoimmunity: are regulatory t cells the cause, the cure, or both?

Regulatory T cells (Tregs) are a specialized subgroup of T-cell lymphocytes that is crucial for maintaining immune homeostasis and preventing excessive immune responses. Depending on their differentiation route, Tregs can be subdivided into thymically derived Tregs (tTregs) and peripherally induced Tregs (pTregs), which originate from conventional T cells after extrathymic differentiation at peripheral sites. Although the regulatory attributes of tTregs and pTregs partially overlap, their modes of action, protein expression profiles, and functional stability exhibit specific characteristics unique to each subset. Over the last few years, our knowledge of Treg differentiation, maturation, plasticity, and correlations between their phenotypes and functions has increased. Genetic and functional studies in patients with numeric and functional Treg deficiencies have contributed to our mechanistic understanding of immune dysregulation and autoimmune pathologies. This review provides an overview of our current knowledge of Treg biology, discusses monogenetic Treg pathologies and explores the role of Tregs in various other autoimmune disorders. Additionally, we discuss novel approaches that explore Tregs as targets or agents of innovative treatment options.

Infections in Disorders of Immune Regulation

Primary immune regulatory disorders (PIRDs) constitute a spectrum of inborn errors of immunity (IEIs) that are primarily characterized by autoimmunity, lymphoproliferation, atopy, and malignancy. In PIRDs, infections are infrequent compared to other IEIs. While susceptibility to infection primarily stems from antibody deficiency, it is sometimes associated with additional innate immune and T or NK cell defects. The use of immunotherapy and chemotherapy further complicates the immune landscape, increasing the risk of diverse infections. Recurrent sinopulmonary infections, particularly bacterial infections such as those associated with staphylococcal and streptococcal organisms, are the most reported infectious manifestations. Predisposition to viral infections, especially Epstein-Barr virus (EBV)-inducing lymphoproliferation and malignancy, is also seen. Notably, mycobacterial and invasive fungal infections are rarely documented in these disorders. Knowledge about the spectrum of infections in these disorders would prevent diagnostic delays and prevent organ damage. This review delves into the infection profile specific to autoimmune lymphoproliferative syndrome (ALPS), Tregopathies, and syndromes with autoimmunity within the broader context of PIRD. Despite the critical importance of understanding the infectious aspects of these disorders, there remains a scarcity of comprehensive reports on this subject.

Case report: A case of novel homozygous LRBA variant induced by chromosomal segmental uniparental disomy - genetic and clinical insights

Objective

The study aims to report a rare case of a novel homozygous variant in the LRBA gene, originating from uniparental disomy of paternal origin. This case contributes new clinical data to the LRBA gene variant database.

Methods

The study details the case of a 2-year-old child diagnosed in May 2023 at our center with a homozygous LRBA gene variant. Detailed clinical data of the patient were collected, including whole-exome sequencing of peripheral blood mononuclear cells, with parental genetic verification.

Results

The child presented with recurrent respiratory infections and chronic neutropenia, progressing to pancytopenia. Imaging showed splenomegaly and enlarged lymph nodes in the axillary and abdominal regions. Peripheral blood lymphocyte count revealed reduced B cells and NK cells. Elevated cytokine levels of IFN-α and IFN-r were observed. Whole-exome sequencing revealed a nonsense homozygous variant in the LRBA gene, specifically c.2584C>T (p.Gln862Ter). The father exhibited a heterozygous variant at this locus, while no variant was found in the mother. Sample analysis indicated characteristics of uniparental disomy. According to the guidelines of the American College of Medical Genetics and Genomics (ACMG), this variant is preliminarily classified as "Likely pathogenic". Currently, there are no reports in academic literature regarding this specific variant site.

Conclusion

LRBA gene variants can lead to a rare inborn error of immunity disease. The c.2584C>T (p.Gln862Ter) variant in exon 22 of the LRBA gene is a newly identified pathogenic variant, and the homozygous variant caused by uniparental disomy is exceedingly rare. This case represents the second global report of an LRBA gene function loss due to uniparental disomy abnormalities.

Therapeutic modalities and clinical outcomes in a large cohort with LRBA deficiency and CTLA4 insufficiency

BACKGROUND

LPS-responsive beige-like anchor (LRBA) deficiency (LRBA-/-) and cytotoxic T-lymphocyte-associated antigen-4 (CTLA4) insufficiency (CTLA4+/-) are mechanistically overlapped diseases presenting with recurrent infections and autoimmunity. The effectiveness of different treatment regimens remains unknown.

OBJECTIVE

Our aim was to determine the comparative efficacy and long-term outcome of therapy with immunosuppressants, CTLA4-immunoglobulin (abatacept), and hematopoietic stem cell transplantation (HSCT) in a single-country multicenter cohort of 98 patients with a 5-year median follow-up.

METHODS

The 98 patients (63 LRBA-/- and 35 CTLA4+/-) were followed and evaluated at baseline and every 6 months for clinical manifestations and response to the respective therapies.

RESULTS

The LRBA-/- patients exhibited a more severe disease course than did the CTLA4+/- patients, requiring more immunosuppressants, abatacept, and HSCT to control their symptoms. Among the 58 patients who received abatacept as either a primary or rescue therapy, sustained complete control was achieved in 46 (79.3%) without severe side effects. In contrast, most patients who received immunosuppressants as primary therapy (n = 61) showed either partial or no disease control (72.1%), necessitating additional immunosuppressants, abatacept, or transplantation. Patients with partial or no response to abatacept (n = 12) had longer disease activity before abatacept therapy, with higher organ involvement and poorer disease outcomes than those with a complete response. HSCT was performed in 14 LRBA-/- patients; 9 patients (64.2%) showed complete remission, and 3 (21.3%) continued to receive immunosuppressants after transplantation. HSCT and abatacept therapy gave rise to similar probabilities of survival.

CONCLUSIONS

Abatacept is superior to immunosuppressants in controlling disease manifestations over the long term, especially when started early, and it may provide a safe and effective therapeutic alternative to transplantation.

Interstitial lung diseases in inborn errors of immunity

PURPOSE OF REVIEW

Our goal is to review current understanding of interstitial lung disease (ILD) affecting patients with inborn errors of immunity (IEI). This includes understanding how IEI might predispose to and promote development or progression of ILD as well as how our growing understanding of IEI can help shape treatment of ILD in these patients. Additionally, by examining current knowledge of ILD in IEI, we hope to identify key knowledge gaps that can become focus of future investigative efforts.

RECENT FINDINGS

Recent identification of novel IEI associated with ILD and the latest reports examining treatment of ILD in IEI are included. Of noted interest, are recent clinical studies of immunomodulatory therapy for ILD in common variable immunodeficiency.

SUMMARY

ILD is a frequent complication found in many IEI. This article provides a guide to identifying manifestations of ILD in IEI. We review a broad spectrum of IEI that develop ILD, including antibody deficiency and immune dysregulation disorders that promote autoimmunity and autoinflammation. This work integrates clinical information with molecular mechanisms of disease and diagnostic assessments to provide an expedient overview of a clinically relevant and expanding topic.

Understanding the Spectrum of Immune Dysregulation Manifestations in Autoimmune Lymphoproliferative Syndrome and Autoimmune Lymphoproliferative Syndrome-like Disorders

As a disorder of immune dysregulation, autoimmune lymphoproliferative syndrome (ALPS) stems from pathogenic variants in the first apoptosis signal-mediated apoptosis (Fas) and Fas-ligand pathway that result in elevations of CD3+ TCRαβ+ CD4- CD8- T cells along with chronic lymphoproliferation, a heightened risk for malignancy, and importantly for the rheumatologist, increased risk of autoimmunity. While immune cytopenias are the most encountered autoimmune phenomena, there is increasing appreciation for ocular, musculoskeletal, pulmonary and renal inflammatory manifestations similar to more common rheumatology diseases. Additionally, ALPS-like conditions that share similar clinical features and opportunities for targeted therapy are increasingly recognized via genetic testing, highlighting the need for rheumatologists to be facile in the recognition and diagnosis of this spectrum of disorders. This review will focus on clinical and laboratory features of both ALPS and ALPS-like disorders with the intent to provide a framework for rheumatologists to understand the pathophysiologic drivers and discriminate between diagnoses.

Expanding IPEX: Inborn Errors of Regulatory T Cells

Regulatory T cells (Tregs) are critical for enforcing peripheral tolerance. Monogenic "Tregopathies" affecting Treg development, stability, and/or function commonly present with polyautoimmunity, atopic disease, and infection. While autoimmune manifestations may present in early childhood, as more disorders are characterized, conditions with later onset have been identified. Treg numbers in the blood may be decreased in Tregopathies, but this is not always the case, and genetic testing should be pursued when there is high clinical suspicion. Currently, hematopoietic cell transplantation is the only curative treatment, but gene therapies are in development, and small molecule inhibitors/biologics may also be used.

Too much of a good thing: a review of primary immune regulatory disorders

Primary immune regulatory disorders (PIRDs) are inborn errors of immunity caused by a loss in the regulatory mechanism of the inflammatory or immune response, leading to impaired immunological tolerance or an exuberant inflammatory response to various stimuli due to loss or gain of function mutations. Whilst PIRDs may feature susceptibility to recurrent, severe, or opportunistic infection in their phenotype, this group of syndromes has broadened the spectrum of disease caused by defects in immunity-related genes to include autoimmunity, autoinflammation, lymphoproliferation, malignancy, and allergy; increasing focus on PIRDs has thus redefined the classical 'primary immunodeficiency' as one aspect of an overarching group of inborn errors of immunity. The growing number of genetic defects associated with PIRDs has expanded our understanding of immune tolerance mechanisms and prompted identification of molecular targets for therapy. However, PIRDs remain difficult to recognize due to incomplete penetrance of their diverse phenotype, which may cross organ systems and present to multiple clinical specialists prior to review by an immunologist. Control of immune dysregulation with immunosuppressive therapies must be balanced against the enhanced infective risk posed by the underlying defect and accumulated end-organ damage, posing a challenge to clinicians. Whilst allogeneic hematopoietic stem cell transplantation may correct the underlying immune defect, identification of appropriate patients and timing of transplant is difficult. The relatively recent description of many PIRDs and rarity of individual genetic entities that comprise this group means data on natural history, clinical progression, and treatment are limited, and so international collaboration will be needed to better delineate phenotypes and the impact of existing and potential therapies. This review explores pathophysiology, clinical features, current therapeutic strategies for PIRDs including cellular platforms, and future directions for research.

Clinical, Radiologic, and Immunologic Features of Patients With CTLA4 Deficiency With Neurologic Involvement

OBJECTIVES

CTLA4 deficiency (CTLA4d) is a disease with multisystem autoimmune features, including neurologic manifestations. We aimed to describe neurologic involvement in these patients.

METHODS

We performed a cross-sectional observational study using the French Reference Centre for Primary Immunodeficiencies (CEREDIH) registry plus a surveillance in national society networks. Participants with confirmed CTLA4d and neurologic involvement were included. Clinical, laboratory, and radiologic features were collected, as well as treatments. Available MRI was double-reviewed.

RESULTS

Among 70 patients with CTLA4d, 13 patients (21%) had neurologic involvement. Neurologic symptoms began at a median age of 18 [15-45] years, mostly occurring after systemic manifestations (median delay: 8.5 [4.5-10.5] years). Main symptoms included headaches, focal deficit (54% each), and seizures (38%). MRI detected at least 1 large contrast-enhancing lesion in 8 patients. Lesions reminiscent of multiple sclerosis lesions were found in 6 patients. Cerebellar (6 patients) and large spinal cord lesions (3 patients) were common. Ten patients were treated with abatacept, of whom 9 (90%) showed good clinical and radiologic response.

DISCUSSION

Neurologic involvement is common among patients with CTLA4d. Despite its rarity, and considering the suspected efficacy of abatacept, neurologists should be aware of the characteristics of CTLA4d neurologic involvement.

Monogenic inborn errors of immunity in autoimmune disorders

To estimate the prevalence of monogenic inborn errors of immunity in patients with autoimmune diseases (AID), the study included 56 subjects (male:female ratio: 1.07) with mean age of onset of autoimmunity 7 years (4 months-46 years). 21/56 had polyautoimmunity. 5/56 patients met the JMF criteria for PID. The different AID referred were hematological (42%) > gastrointestinal (GI) (16%) > skin (14%) > endocrine (10%) > rheumatological (8%) > renal (6%) > neurological (2%). 36/56 reported recurrent infections. 27/56 were on polyimmunotherapy. 18/52 (35%) had CD19 lymphopenia, 24/52 (46%) had CD4 lymphopenia, 11/52 (21%) had CD8 lymphopenia, and 14/48 (29%) had NK lymphopenia. 21/50 (42%) had hypogammaglobinemia; 3 of whom were given rituximab. 28/56 were found to have pathogenic variants among PIRD genes. These 28 patients had 42 AID among which hematological was most common (50%) > GI (14%) = skin (14%)> endocrine (9%) > rheumatological (7%) > renal and neurological (2%). Hematological AID was the most common AID (75%) in children with PIRD. Positive predictive value (PPV) of abnormal immunological tests was 50% and sensitivity of 70%. JMF criteria had specificity of 100% in identifying PIRD and sensitivity of 17%. Polyautoimmunity had a PPV of 35% and sensitivity of 40%. 11/28 of these children were offered transplant. 8/28 were started on sirolimus, 2/28 on abatacept, and 3/28 on baricitinib/ruxolitinib after diagnosis. In conclusion, 50% of children with AID have underlying PIRD. LRBA deficiency and STAT1 GOF were the most common PIRD. Age at presentation, number of autoimmunity, routine immunological tests, and JMF criteria are not predictive of underlying PIRD. Early diagnosis with exome sequencing alters the prognosis and opens new therapeutic avenue.

Paediatric-onset Evans syndrome: Breaking away from refractory immune thrombocytopenia

Since its first description by Evans in 1951, this syndrome has been linked to chronic immune thrombocytopenia with the concurrent or delayed onset of autoimmune haemolytic anaemia or neutropenia. For decades, the evolution of Evans syndrome (ES) has carried a poor prognosis and often resulted in chronic steroid exposure, multiple immune suppressing medications directed against T or B lymphocytes, and splenectomy. This paper presents a new view of ES based on recent advances in genomics which begin to classify patients based on their underlying molecular variants in previously described primary immune disorders. This has opened up new avenues of targeted therapy or bone marrow transplant at rather than broad long-term immune suppression or splenectomy. Importantly, recent studies of the full lifespan of ES suggest that at least 80% of those paediatric patients will progress to various clinical or biological immunopathological manifestations with age despite the resolution of their cytopenias. Those patients merit long-term follow-up and monitoring in dedicated transition programs to improve outcome at the adult age.

Efficacy of abatacept treatment in a patient with enteropathy carrying a variant of unsignificance in CTLA4 gene: A case report

BACKGROUND

Cytotoxic T Lymphocyte Antigen-4 (CTLA4) deficiency is a genetic defect that causes a common variable immunodeficiency (CVID) clinical phenotype. Several studies have reported an association between CTLA mutations or variants and various autoimmune diseases. Targeted therapy models, which have become increasingly popular in recent years, have been successful in treating CTLA4 deficiency. In this article, we discuss the clinical outcomes of abatacept treatment in a patient with CTLA4 and lipopolysaccharide-responsive beige-like anchor (LRBA) variants that was previously diagnosed with CVID.

CASE SUMMARY

A 25-year-old female patient, who was visibly cachectic, visited our clinic over the course of five years, complaining of diarrhea. The patient was diagnosed with ulcerative colitis in the centers she had visited previously, and various treatments were administered; however, clinical improvement could not be achieved. Severe hypokalemia was detected during an examination. Her serum immunoglobulin levels, CD19+ B-cell percentage, and CD4/CD8 ratio were low. An endoscopic examination revealed erosive gastritis, nodular duodenitis, and pancolitis. Histopathological findings supported the presence of immune mediated enteropathy. When the patient was examined carefully, she was diagnosed with CVID, and intravenous immunoglobulin treatment was initiated. Peroral and rectal therapeutic drugs including steroid therapy episodes were administered to treat the immune mediated enteropathy. Strict follow-ups and treatment were performed due to the hypokalemia. After conducting genetic analyses, the CTLA4 and LRBA variants were identified and abatacept treatment was initiated. With targeted therapy, the patient's clinical and laboratory findings rapidly regressed, and there was an increase in weight.

CONCLUSION

The heterozygous CTLA4 variant identified in the patient has been previously shown to be associated with various autoimmune diseases. The successful clinical outcome of abatacept treatment in this patient supports the idea that this variant plays a role in the immunopathogenesis of the disease. In the presence of severe disease, abatacept therapy should be considered until further testing can be conducted.

Central nervous system manifestations of LRBA deficiency: case report of two siblings and literature review

BACKGROUND

LPS-responsive beige-like anchor protein (LRBA) deficiency is a primary immunodeficiency disease (PID) characterized by a regulatory T cell defect resulting in immune dysregulation and autoimmunity. We present two siblings born to consanguineous parents of North African descent with LRBA deficiency and central nervous system (CNS) manifestations. As no concise overview of these manifestations is available in literature, we compared our patient's presentation with a reviewed synthesis of the available literature.

CASE PRESENTATIONS

The younger brother presented with enteropathy at age 1.5 years, and subsequently developed Evans syndrome and diabetes mellitus. These autoimmune manifestations led to the genetic diagnosis of LRBA deficiency through whole exome sequencing with PID gene panel. At 11 years old, he had two tonic-clonic seizures. Brain MRI showed multiple FLAIR-hyperintense lesions and a T2-hyperintense lesion of the cervical medulla.  His sister presented with immune cytopenia at age 9 years, and developed diffuse lymphadenopathy and interstitial lung disease. Genetic testing confirmed the same mutation as her brother. At age 13 years, a brain MRI showed multiple T2-FLAIR-hyperintense lesions. She received an allogeneic hematopoietic stem cell transplantation (allo-HSCT) 3 months later. Follow-up MRI showed regression of these lesions.

CONCLUSIONS

Neurological disease is documented in up to 25% of patients with LRBA deficiency. Manifestations range from cerebral granulomas to acute disseminating encephalomyelitis, but detailed descriptions of neurological and imaging phenotypes are lacking. LRBA deficiency amongst other PIDs should be part of the differential diagnosis in patients with inflammatory brain lesions. We strongly advocate for a more detailed description of CNS manifestations in patients with LRBA deficiency, when possible with MR imaging. This will aid clinical decision concerning both anti-infectious and anti-inflammatory therapy and in considering the indication for allo-HSCT.

Type 1 diabetes and inborn errors of immunity: Complete strangers or 2 sides of the same coin?

Type 1 diabetes (T1D) is a polygenic disease and does not follow a mendelian pattern. Inborn errors of immunity (IEIs), on the other hand, are caused by damaging germline variants, suggesting that T1D and IEIs have nothing in common. Some IEIs, resulting from mutations in genes regulating regulatory T-cell homeostasis, are associated with elevated incidence of T1D. The genetic spectrum of IEIs is gradually being unraveled; consequently, molecular pathways underlying human monogenic autoimmunity are being identified. There is an appreciable overlap between some of these pathways and the genetic variants that determine T1D susceptibility, suggesting that after all, IEI and T1D are 2 sides of the same coin. The study of monogenic IEIs with a variable incidence of T1D has the potential to provide crucial insights into the mechanisms leading to T1D. These insights contribute to the definition of T1D endotypes and explain disease heterogeneity. In this review, we discuss the interconnected pathogenic pathways of autoimmunity, β-cell function, and primary immunodeficiency. We also examine the role of environmental factors in disease penetrance as well as the circumstantial evidence of IEI drugs in preventing and curing T1D in individuals with IEIs, suggesting the repositioning of these drugs also for T1D therapy.

Unmasking a fungal fire

Immune checkpoint inhibitor (ICI) therapy represents a breakthrough cancer treatment by stimulating dysfunctional T cells in the tumour environment to kill cancer cells. Beyond effects on anticancer immunity, ICI therapy may be associated with increased susceptibility to or more rapid resolution of chronic infections, particularly those caused by human fungal pathogens. In this concise review, we summarise recent observations and findings that implicate immune checkpoint blockade in fungal infection outcomes.

Impact of age at diagnosis, sex, and immunopathological manifestations in 886 patients with pediatric chronic immune thrombocytopenia

Pediatric chronic immune thrombocytopenia (cITP) is a heterogeneous condition in terms of bleeding severity, second-line treatment use, association with clinical and/or biological immunopathological manifestations (IMs), and progression to systemic lupus erythematosus (SLE). No risk factors for these outcomes are known. Specifically, whether age at ITP diagnosis, sex, or IMs impact cITP outcomes is unknown. We report the outcomes of patients with pediatric cITP from the French nationwide prospective cohort OBS'CEREVANCE. We used multivariate analyses to investigate the effect of age at ITP diagnosis, sex, and IMs on cITP outcomes. We included 886 patients with a median (min-max) follow-up duration of 5.3 (1.0-29.3) years. We identified an age cutoff that dichotomized the risk of the outcomes and defined two risk groups: patients with ITP diagnosed <10 years (children) and ≥ 10 years (adolescents). Adolescents had a two to four-fold higher risk of grade ≥3 bleeding, second-line treatment use, clinical and biological IMs, and SLE diagnosis. Moreover, female sex and biological IMs were independently associated with higher risks of biological IMs and SLE diagnosis, second-line treatment use, and SLE diagnosis, respectively. The combination of these three risk factors defined outcome-specific risk groups. Finally, we showed that patients clustered in mild and severe phenotypes, more frequent in children and adolescents, respectively. In conclusion, we identified that age at ITP diagnosis, sex, and biological IMs impacted the long-term outcomes of pediatric cITP. We defined risk groups for each outcome, which will help clinical management and further studies.

Beyond IBD: the genetics of other early-onset diarrhoeal disorders

Diarrhoeal disorders in childhood extend beyond the inflammatory bowel diseases. Persistent and severe forms of diarrhoea can occur from birth and are associated with significant morbidity and mortality. These disorders can affect not only the gastrointestinal tract but frequently have extraintestinal manifestations, immunodeficiencies and endocrinopathies. Genomic analysis has advanced our understanding of these conditions and has revealed precision-based treatment options such as potentially curative haematopoietic stem cell transplant. Although many new mutations have been discovered, there is frequently no clear genotype-phenotype correlation. The functional effects of gene mutations can be studied in model systems such as patient-derived organoids. This allows us to further characterise these disorders and advance our understanding of the pathophysiology of the intestinal mucosa. In this review, we will provide an up to date overview of genes involved in diarrhoeal disorders of early onset, particularly focussing on the more recently described gene defects associated with protein loosing enteropathy.

Common Variable Immunodeficiency: More Pathways than Roads to Rome

Fifty years have elapsed since the term common variable immunodeficiency (CVID) was introduced to accommodate the many and varied antibody deficiencies being identified in patients with suspected inborn errors of immunity (IEIs). Since then, how the term is understood and applied for diagnosis and management has undergone many revisions, though controversy persists on how exactly to define and classify CVID. Many monogenic disorders have been added under its aegis, while investigations into polygenic, epigenetic, and somatic contributions to CVID susceptibility have gained momentum. Expansion of the overall IEI landscape has increasingly revealed genotypic and phenotypic overlap between CVID and various other immunological conditions, while increasingly routine genotyping of CVID patients continues to identify an incredible diversity of pathophysiological mechanisms affecting even single genes. Though many questions remain to be answered, the lessons we have already learned from CVID biology have greatly informed our understanding of adaptive, but also innate, immunity.

Comparing the levels of CTLA-4-dependent biological defects in patients with LRBA deficiency and CTLA-4 insufficiency

BACKGROUND

Lipopolysaccharide-responsive beige-like anchor protein (LRBA) deficiency and cytotoxic T-lymphocyte protein-4 (CTLA-4) insufficiency are recently described disorders that present with susceptibility to infections, autoimmunity, and lymphoproliferation. Clinical and immunological comparisons of the diseases with long-term follow-up have not been previously reported. We sought to compare the clinical and laboratory manifestations of both diseases and investigate the role of flow cytometry in predicting the genetic defect in patients with LRBA deficiency and CTLA-4 insufficiency.

METHODS

Patients were evaluated clinically with laboratory assessments for lymphocyte subsets, T follicular helper cells (T_FH ), LRBA expression, and expression of CD25, FOXP3, and CTLA4 in regulatory T cells (Tregs) at baseline and 16 h post-stimulation.

RESULTS

LRBA-deficient patients (n = 29) showed significantly early age of symptom onset, higher rates of pneumonia, autoimmunity, chronic diarrhea, and failure to thrive compared to CTLA-4 insufficiency (n = 12). In total, 29 patients received abatacept with favorable responses and the overall survival probability was not different between transplanted versus non-transplanted patients in LRBA deficiency. Meanwhile, higher probability of survival was observed in CTLA-4-insufficient patients (p = 0.04). The T-cell subsets showed more deviation to memory cells in CTLA-4-insufficiency, accompanied by low percentages of Treg and dysregulated cT_FH cells response in both diseases. Cumulative numbers of autoimmunities positively correlated with cT_FH frequencies. Baseline CTLA-4 expression was significantly diminished in LRBA deficiency and CTLA-4 insufficiency, but significant induction in CTLA-4 was observed after short-term T-cell stimulation in LRBA deficiency and controls, while this elevation was less in CTLA-4 insufficiency, allowing to differentiate this disease from LRBA deficiency with high sensitivity (87.5%) and specificity (90%).

CONCLUSION

This cohort provided detailed clinical and laboratory comparisons for LRBA deficiency and CTLA-4 insufficiency. The flow cytometric approach is useful in predicting the defective gene; thus, targeted sequencing can be conducted to provide rapid diagnosis and treatment for these diseases impacting the CTLA-4 pathway.

Clinical, immunological, molecular and therapeutic findings in monogenic immune dysregulation diseases: Middle East and North Africa registry

Monogenic immune dysregulation diseases (MIDD) are caused by defective immunotolerance. This study was designed to increase knowledge on the prevalence and spectrum of MIDDs, genetic patterns, and outcomes in Middle East and North Africa (MENA). MIDD patients from 11 MENA countries (Iran, Turkey, Kuwait, Oman, Algeria, Egypt, United Arab Emirates, Tunisia, Jordan, Qatar, and Azerbaijan) were retrospectively evaluated. 343 MIDD patients (58% males and 42% female) at a median (IQR) age of 101 (42-192) months were enrolled. The most common defective genes were LRBA (23.9%), LYST (8.2%), and RAB27A (7.9%). The most prevalent initial and overall manifestations were infections (32.2% and 75.1%), autoimmunity (18.6% and 41%), and organomegaly (13.3% and 53.8%), respectively. Treatments included immunoglobulin replacement therapy (53%), hematopoietic stem cell transplantation (HSCT) (14.3%), immunosuppressives (36.7%), and surgery (3.5%). Twenty-nine (59.2%) patients survived HSCT. Along with infectious complications, autoimmunity and organomegaly may be the initial or predominant manifestations of MIDD.

Autoimmune Cytopenias in Common Variable Immunodeficiency Are a Diagnostic and Therapeutic Conundrum: An Update

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency (PID). CVID is a heterogenous condition and clinical manifestations may vary from increased susceptibility to infections to autoimmune manifestations, granulomatous disease, polyclonal lymphoproliferation, and increased risk of malignancy. Autoimmune manifestations may, at times, be the first and only clinical presentation of CVID, resulting in diagnostic dilemma for the treating physician.

Autoimmune cytopenias (autoimmune haemolytic anaemia and/or thrombocytopenia) are the most common autoimmune complications seen in patients with CVID. Laboratory investigations such as antinuclear antibodies, direct Coomb’s test and anti-platelet antibodies may not be useful in patients with CVID because of lack of specific antibody response. Moreover, presence of autoimmune cytopenias may pose a significant therapeutic challenge as use of immunosuppressive agents can be contentious in these circumstances. It has been suggested that serum immunoglobulins must be checked in all patients presenting with autoimmune cytopenia such as immune thrombocytopenia or autoimmune haemolytic anaemia.

It has been observed that patients with CVID and autoimmune cytopenias have a different clinical and immunological profile as compared to patients with CVID who do not have an autoimmune footprint. Monogenic defects have been identified in 10-50% of all patients with CVID depending upon the population studied. Monogenic defects are more likely to be identified in patients with CVID with autoimmune complications. Common genetic defects that may lead to CVID with an autoimmune phenotype include nuclear factor kappa B subunit 1 (NF-kB1), Lipopolysaccharide (LPS)-responsive beige-like anchor protein (LRBA), cytotoxic T lymphocyte antigen 4 (CTLA4), Phosphoinositide 3-kinase (PI3K), inducible T-cell costimulatory (ICOS), IKAROS and interferon regulatory factor-2 binding protein 2 (IRF2BP2).

In this review, we update on recent advances in pathophysiology and management of CVID with autoimmune cytopenias.

LRBA Deficiency Can Lead to Lethal Colitis That Is Diminished by SHIP1 Agonism

Humans homozygous for inactivating LRBA (lipopolysaccharide (LPS)-responsive beige-like anchor) mutations or with compound heterozygous mutations exhibit a spectrum of immune-related pathologies including inflammatory bowel disease (IBD). The cause of this pathology remains undefined. Here we show that disruption of the colon epithelial barrier in LRBA-deficient mice by dextran sulfate sodium (DSS) consumption leads to severe and uniformly lethal colitis. Analysis of bone marrow (BM) chimeras showed that susceptibility to lethal colitis is primarily due to LRBA deficiency in the immune compartment and not the gut epithelium. Further dissection of the immune defect in LRBA-deficient hosts showed that LRBA is essential for the expression of CTLA4 by Treg cells and IL22 and IL17 expression by ILC3 cells in the large intestine when the gut epithelium is compromised by DSS. We further show that SHIP1 agonism partially abrogates the severity and lethality of DSS-mediated colitis. Our findings indicate that enteropathy induced by LRBA deficiency has multiple causes and that SHIP1 agonism can partially abrogate the inflammatory milieu in the gut of LRBA-deficient hosts.

Inborn errors of immunity and immunodeficiencies: antibody-mediated pathology and autoimmunity as a consequence of impaired immune reactions

B cell tolerance to self-antigen is an active process that requires the temporal and spatial integration of signals of defined intensity. In common variable immune deficiency disorders (CVID), CTLA-4 deficiency, autoimmune lymphoproliferative syndrome (ALPS), or in collagen VII deficiency, genetic defects in molecules regulating development, activation, maturation and extracellular matrix composition alter the generation of B cells, resulting in immunodeficiency. Paradoxically, at the same time, the defective immune processes favor autoantibody production and immunopathology through impaired establishment of tolerance. The development of systemic autoimmunity in the framework of defective BCR signaling is relatively unusual in genetic mouse models. In sharp contrast, such reduced signaling in humans is clearly linked to pathological autoimmunity. The molecular mechanisms by which tolerance is broken in these settings are only starting to be explored resulting in novel therapeutic interventions. For instance, in CTLA-4 deficiency, homeostasis can be restored by CTLA-4 Ig treatment. Following this example, the identification of the molecular targets causing the reduced signals and their restoration is a visionary way to reestablish tolerance and develop novel therapeutic avenues for immunopathologies. This article is protected by copyright. All rights reserved.

GVHD, IBD and primary immunodeficiencies: The gut as a target of immunopathology resulting from impaired immunity

The intestinal tract is the largest immunological organ in the body and has a central function of regulating local immune responses, as the intestinal epithelial barrier is a location where the immune system interacts with the gut microbiome including bacteria, fungi and viruses. Impaired immunity in the intestinal tract can lead to immunopathology, which manifests in different diseases such as inflammatory bowel disease (IBD) or intestinal graft-versus-host disease (GVHD). A disturbed communication between epithelial cells, immune cells and microbiome will shape pathogenic immune responses to antigens, which need to be counterbalanced by tolerogenic mechanisms and repair mechanisms. Here, we review how impaired intestinal immune function leads to immunopathology with a specific focus on innate immune cells, the role of the microbiome and the resulting clinical manifestations including intestinal GVHD, IBD and enteropathy in primary immunodeficiency. This article is protected by copyright. All rights reserved.

Druggable monogenic immune defects hidden in diverse medical specialties: Focus on overlap syndromes

In the last two decades two new paradigms changed our way of perceiving primary immunodeficiencies: An increasing number of immune defects are more associated with inflammatory or autoimmune features rather than with infections. Some primary immune defects are due to hyperactive pathways that can be targeted by specific inhibitors, providing innovative precision treatments that can change the natural history of diseases. In this article we review some of these "druggable" inborn errors of immunity and describe how they can be suspected and diagnosed in diverse pediatric and adult medicine specialties. Since the availability of precision treatments can dramatically impact the course of these diseases, preventing the development of organ damage, it is crucial to widen the awareness of these conditions and to provide practical hints for a prompt detection and cure.

Clinical Courses of IKAROS and CTLA4 Deficiencies: A Systematic Literature Review and Retrospective Longitudinal Study

IKAROS and CTLA4 deficiencies are inborn errors of immunity and show similar clinical phenotypes, including hypogammaglobulinemia and autoimmune diseases (ADs). However, the differences in clinical features and pathogenesis of these are not fully understood. Therefore, we performed systematic literature reviews for IKAROS and CTLA4 deficiencies. The reviews suggested that patients with IKAROS deficiency develop AD earlier than hypogammaglobulinemia. However, no study assessed the detailed changes in clinical manifestations over time; this was likely due to the cross-sectional nature of the studies. Therefore, we conducted a retrospective longitudinal study on IKAROS and CTLA4 deficiencies in our cohort to evaluate the clinical course over time. In patients with IKAROS deficiency, AD and hypogammaglobulinemia often develop in that order, and AD often resolves before the onset of hypogammaglobulinemia; these observations were not found in patients with CTLA4 deficiency. Understanding this difference in the clinical course helps in the clinical management of both. Furthermore, our results suggest B- and T-cell-mediated ADs in patients with IKAROS and CTLA4 deficiencies, respectively.

Beyond Infections: New Warning Signs for Inborn Errors of Immunity in Children

Patients with inborn errors of immunity (IEI) are susceptible to developing a severe infection-related clinical phenotype, but the clinical consequences of immune dysregulation, expressed with autoimmunity, atopy, and lymphoproliferation could represent the first sign in a significant percentage of patients. Therefore, during the diagnostic work-up patients with IEI are frequently addressed to different specialists, including endocrinologists, rheumatologists, and allergologists, often resulting in a delayed diagnosis. In this paper, the most relevant non-infectious manifestations of IEI are discussed. Particularly, we will focus on the potential presentation of IEI with autoimmune cytopenia, non-malignant lymphoproliferation, severe eczema or erythroderma, autoimmune endocrinopathy, enteropathy, and rheumatologic manifestations, including vasculitis and systemic lupus erythematosus. This paper aims to identify new warning signs to suspect IEI and help in the identification of patients presenting with atypical/non-infectious manifestations.

A sporadic case of CTLA4 haploinsufficiency manifesting as Epstein-Barr virus-positive diffuse large B-cell lymphoma

Cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) is a coinhibitory receptor that plays an essential role in maintaining immune system homeostasis by suppressing T-cell activation. We report a sporadic case of CTLA4 haploinsufficiency in a patient with Epstein–Barr virus-positive diffuse large B-cell lymphoma and subsequent benign lymphadenopathy. A missense mutation in exon 2 of the CTLA4 gene (c.251T>C, p.V84A) was found in the patient’s peripheral blood and buccal cell DNA, but not in her parents’ DNA. CTLA4 expression decreased in the peripheral regulatory T cells upon stimulation, whereas CTLA4 and PD-1-positive T cell subsets increased, possibly to compensate for the defective CTLA4 function. This case suggests that some adult lymphoma patients with no remarkable medical history have primary immune disorder. As immune-targeted therapies are now widely used for the treatment of malignancies, it is increasingly important to recognize the underlying primary immune disorders to properly manage the disease and avoid unexpected complications of immunotherapies.

Development of preclinical and clinical models for immune-related adverse events following checkpoint immunotherapy: a perspective from SITC and AACR

Recent advances in cancer immunotherapy have completely revolutionized cancer treatment strategies. Nonetheless, the increasing incidence of immune-related adverse events (irAEs) is now limiting the overall benefits of these treatments. irAEs are well-recognized side effects of some of the most effective cancer immunotherapy agents, including antibody blockade of the cytotoxic T-lymphocyte-associated protein 4 and programmed death protein 1/programmed-death ligand 1 pathways. To develop an action plan on the key elements needed to unravel and understand the key mechanisms driving irAEs, the Society for Immunotherapy for Cancer and the American Association for Cancer Research partnered to bring together research and clinical experts in cancer immunotherapy, autoimmunity, immune regulation, genetics and informatics who are investigating irAEs using animal models, clinical data and patient specimens to discuss current strategies and identify the critical next steps needed to create breakthroughs in our understanding of these toxicities. The genetic and environmental risk factors, immune cell subsets and other key immunological mediators and the unique clinical presentations of irAEs across the different organ systems were the foundation for identifying key opportunities and future directions described in this report. These include the pressing need for significantly improved preclinical model systems, broader collection of biospecimens with standardized collection and clinical annotation made available for research and integration of electronic health record and multiomic data with harmonized and standardized methods, definitions and terminologies to further our understanding of irAE pathogenesis. Based on these needs, this report makes a set of recommendations to advance our understanding of irAE mechanisms, which will be crucial to prevent their occurrence and improve their treatment.

Challenging Mimickers in the Diagnosis of Sarcoidosis: A Case Study

Sarcoidosis is a systemic granulomatous disease of unknown cause characterized by a wide variety of presentations. Its diagnosis is based on three major criteria: a clinical presentation compatible with sarcoidosis, the presence of non-necrotizing granulomatous inflammation in one or more tissue samples, and the exclusion of alternative causes of granulomatous disease. Many conditions may mimic a sarcoid-like granulomatous reaction. These conditions include infections, neoplasms, immunodeficiencies, and drug-induced diseases. Moreover, patients with sarcoidosis are at risk of developing opportunistic infections or lymphoma. Reliably confirming the diagnosis of sarcoidosis and better identifying new events are major clinical problems in daily practice. To address such issues, we present seven emblematic cases, seen in our department, over a ten-year period along with a literature review about case reports of conditions misdiagnosed as sarcoidosis.

Lymphadenopathy at the crossroad between immunodeficiency and autoinflammation: An intriguing challenge

Lymphadenopathies can be part of the clinical spectrum of several primary immunodeficiencies, including diseases with immune dysregulation and autoinflammatory disorders, as the clinical expression of benign polyclonal lymphoproliferation, granulomatous disease or lymphoid malignancy. Lymphadenopathy poses a significant diagnostic dilemma when it represents the first sign of a disorder of the immune system, leading to a consequently delayed diagnosis. Additionally, the finding of lymphadenopathy in a patient with diagnosed immunodeficiency raises the question of the differential diagnosis between benign lymphoproliferation and malignancies. Lymphadenopathies are evidenced in 15–20% of the patients with common variable immunodeficiency, while in other antibody deficiencies the prevalence is lower. They are also evidenced in different combined immunodeficiency disorders, including Omenn syndrome, which presents in the first months of life. Interestingly, in the activated phosphoinositide 3‐kinase delta syndrome, autoimmune lymphoproliferative syndrome, Epstein–Barr virus (EBV)‐related lymphoproliferative disorders and regulatory T cell disorders, lymphadenopathy is one of the leading signs of the entire clinical picture. Among autoinflammatory diseases, the highest prevalence of lymphadenopathies is observed in patients with periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) and hyper‐immunoglobulin (Ig)D syndrome. The mechanisms underlying lymphoproliferation in the different disorders of the immune system are multiple and not completely elucidated. The advances in genetic techniques provide the opportunity of identifying new monogenic disorders, allowing genotype–phenotype correlations to be made and to provide adequate follow‐up and treatment in the single diseases. In this work, we provide an overview of the most relevant immune disorders associated with lymphadenopathy, focusing on their diagnostic and prognostic implications.