Clinical, Immunological, and Genetic Features in Patients with Activated PI3Kδ Syndrome (APDS): a Systematic Review

A randomised, placebo-controlled, phase III trial of leniolisib in activated phosphoinositide 3-kinase delta (PI3Kδ) syndrome (APDS): Adolescent and adult subgroup analysis

Activated phosphoinositide 3-kinase delta (PI3Kδ) syndrome (APDS) is an ultra-rare, progressive genetic disease, characterised by immune deficiency and dysregulation, affecting individuals from birth. In a 12-week phase III randomised placebo-controlled trial, leniolisib, a selective PI3Kδ inhibitor, was well-tolerated and met both co-primary endpoints (change from Baseline in log10-transformed sum of product of diameters of index lymph nodes and percentage of naïve/total B cells at Day 85). Here, prespecified subgroup analyses are reported in adolescents aged 12-17 years (leniolisib, n = 8; placebo, n = 4) and adults aged ≥18 (leniolisib, n = 13; placebo, n = 6). In both subgroups, leniolisib reduced lymphadenopathy (least squares mean change versus placebo: adolescents, -0.4 versus -0.1; adults, -0.3 versus 0.1) and increased the percentage of naïve B cells (least squares mean change: adolescents, 44.5 versus -16.5; adults, 28.4 versus -1.1). Leniolisib was well-tolerated in both adolescents and adults. These results show leniolisib is an effective APDS treatment in both subpopulations. PLAIN LANGUAGE SUMMARY: What is activated PI3Kδ syndrome (APDS)? APDS is an ultra-rare disease in which the immune system does not work correctly. People with APDS have a wide range of symptoms, including infections, certain organs associated with the immune system becoming larger, and worse quality of life. These symptoms generally start in childhood. Why was this study carried out? Current treatments only treat the symptoms of APDS, rather than correcting the cause of the problem. These treatments can also have significant side effects. A new medication for APDS called leniolisib aims to treat the underlying cause of the disease. This publication reports results from a clinical trial of leniolisib which compared patients who received leniolisib with patients who received a placebo. The aim of this report was to examine these clinical trial results to understand if leniolisib is effective and safe when treating both adolescents (12-17 years old) and adults (18 years and older) with APDS. What were the results of this study? Leniolisib improved the number of certain immune cells, compared to patients who did not receive leniolisib, in both adolescents and adults with APDS. Leniolisib also reduced the size of the enlarged immune system organs in both adolescents and adults with APDS. There were no major safety concerns for either age group who received leniolisib. What do these results mean? These results show that leniolisib can help the immune system to work in a way that is closer to those without APDS. This new treatment is effective and generally well-tolerated for both adolescents and adults. These results indicate that people with APDS are able to start treatment with leniolisib during adolescence, which may slow the build-up of symptoms and may also have a positive impact on the quality of their lives.

Common variable immunodeficiency: autoimmune cytopenias and advances in molecular diagnosis

Common variable immunodeficiency (CVID) is one of the most common groups of human inborn errors of immunity. In addition to infections resulting from insufficient levels of immunoglobulins and antibodies, a significant proportion of patients develop autoimmune cytopenias, especially immune thrombocytopenia, hemolytic anemia, or neutropenia. They may be the initial manifestation of CVID in a patient who has not had significant infections, and similar episodes may recur at intervals over time. Treatment of these hematologic complications includes the use of corticosteroids or other medications, often including rituximab; splenectomy is discouraged. Here we outline the overall occurrence of these blood cytopenias in a cohort of 408 patients, as well as the clinical and genetic associations noted in these individuals.

Genetic Etiologies and Outcomes in Malignancy and Mortality in Activated Phosphoinositide 3-Kinase Delta Syndrome: A Systematic Review

INTRODUCTION

This analysis evaluated literature on patients with activated phosphoinositide 3-kinase delta syndrome (APDS) to better understand the genetic etiologies and occurrence of mortality in this population.

METHODS

A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses approach, including all articles published in English prior to March 13, 2023, in PubMed and Embase. Patients included in the study had reported either (1) APDS diagnosis or (2) ≥ 1 clinical sign consistent with APDS and a first-degree relative with genetically confirmed APDS. Reported age at last observation was also a required outcome. Publications not meeting these criteria were excluded. Data were summarized using descriptive statistics.

RESULTS

The search identified 108 publications describing 351 unique patients with 39 distinct disease-causing variants. Among these, 41 (12%) deaths were reported, with a mean age at last follow-up of 19.6 (range, 1-64) years. A cause of death was reported for 80% (33/41) of deaths; lymphoma (24%, 10/41) and infections (22%, 9/41) were the most common causes. Types of infections causing death were severe uncontrollable infections (n = 3), sepsis (n = 2), viral infection (varicella zoster pneumonitis [n = 1], cytomegalovirus and adenovirus [n = 1], and Epstein-Barr virus [n = 1]), and infection (n = 1). Mean age at death for lymphoma was 24.9 (range, 1-41) years, and all nine patients who died from infections died before the age of 15 years. The mean age at first APDS symptom was 2.0 (range, < 1-22) years, and mean age at APDS diagnosis was 13.4 (range, 0-56) years; the mean time between symptoms and diagnosis was 10.6 (range, 0-44) years. Limitations of the study were primarily related to the data source.

CONCLUSION

Patients with APDS suffer early mortality, largely from lymphoma and infection, with large time gaps between symptoms and diagnosis. These findings highlight the need for improved diagnostics, earlier genetic testing for APDS, increased awareness of familial testing, and targeted therapies.

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.

Case Report: Early-onset or recalcitrant cytopenias as presenting manifestations of activated PI3Kδ syndrome

Background

Patients with recurrent, chronic, or refractory cytopenias represent a challenging subgroup that may harbor an underlying diagnosis, such as an inborn error of immunity (IEI). Patients with IEIs such as activated phosphoinositide 3-kinase delta syndrome (APDS), frequently have hematologic manifestations, but these are not often reported as presenting symptoms. As a result, IEIs may be overlooked in patients presenting with early and/or recalcitrant cytopenias. Here, we describe the diagnostic journey and management of three patients who presented to a pediatric hematologist/oncologist with early-onset or recalcitrant cytopenias and were ultimately diagnosed with APDS.

Case presentations

Patients presented with early-onset and/or refractory cytopenias, with two of the three developing multilineage cytopenias. Prior to an APDS diagnosis, two patients underwent a total of approximately 20 procedures, including biopsies, invasive endoscopies, and imaging, with one undergoing eight differential diagnoses that were ruled out through additional testing. Recalcitrant cytopenias, a history of infection, and a family history of lymphoproliferation, infection, or autoimmunity raised suspicion of an underlying IEI, leading to genetic testing. Genetic testing identified a pathogenic variant of PIK3CD in each patient, resulting in the diagnosis of APDS. Following these diagnoses, two patients underwent modifications in the management of care with the administration of intravenous immunoglobulin therapy (IVIG), the mTOR inhibitor sirolimus, or surgical procedures. These treatment modifications either improved or resolved the cytopenias. The third patient showed improvement in immune thrombocytopenia with IVIG 1 month prior to receiving a definitive diagnosis. Following diagnosis, follow-up genetic testing of family members led to the identification of additional cases of APDS.

Conclusions

These cases highlight the importance of early genetic evaluation in patients with early-onset or recalcitrant cytopenias and demonstrate the challenges of differential diagnosis. In addition, these cases demonstrate beneficial changes in management and outcomes that can follow a definitive diagnosis, including the identification of targeted treatment options. Collectively, this case series supports the notion that underlying IEIs should be considered in the workup of early-onset or recalcitrant cytopenias, particularly in patients who present with a combination of hematologic and immunologic manifestations that are refractory to treatment, manifest at an unusually young age, or can be tied to family history.

Hyperactivation of the PI3K pathway in inborn errors of immunity: current understanding and therapeutic perspectives

The phosphoinositide-3-kinase (PI3K) pathway function is crucial to the normal development, differentiation, and function of immune cells including B, T, and NK cells. Following the description of two cohorts of patients with an inboirn error of immunity (also known as primary immunodeficiency) with gain-of-function variants in the PIK3CD gene a decade ago, the disease entity activated PI3K delta syndrome (APDS) was named. Since then, many more patients with PIK3CD variants have been described, and loss-of-function variants in PIK3R1 and PTEN have also been linked to APDS. Importantly, the availability of small molecules that inhibit the PI3K pathway has enabled targeted treatment of APDS patients. In this review, we define (i) the PI3K pathway and its role in inborn errors of immunity; (ii) the clinical and immunological presentation of APDS1 (PIK3CD GOF), APDS2 (PIK3R1 LOF), and related disorders; (iii) Diagnostic approaches to identify and functionally validate the genetic causes of disease; (iv) therapeutic interventions to target PI3K hyperactivation; and finally (v) current challenges and future perspectives that require attention for the optimal treatment of patients with APDS and APDS-L diseases.

Paradoxical dominant negative activity of an immunodeficiency-associated activating PIK3R1 variant

PIK3R1 encodes three regulatory subunits of class IA phosphoinositide 3-kinase (PI3K), each associating with any of three catalytic subunits, namely p110α, p110β or p110δ. Constitutional PIK3R1 mutations cause diseases with a genotype-phenotype relationship not yet fully explained: heterozygous loss-of-function mutations cause SHORT syndrome, featuring insulin resistance and short stature attributed to reduced p110α function, while heterozygous activating mutations cause immunodeficiency, attributed to p110δ activation and known as APDS2. Surprisingly, APDS2 patients do not show features of p110α hyperactivation, but do commonly have SHORT syndrome-like features, suggesting p110α hypofunction. We sought to investigate this. In dermal fibroblasts from an APDS2 patient, we found no increased PI3K signalling, with p110δ expression markedly reduced. In preadipocytes, the APDS2 variant was potently dominant negative, associating with Irs1 and Irs2 but failing to heterodimerise with p110α. This attenuation of p110α signalling by a p110δ-activating PIK3R1 variant potentially explains co-incidence of gain-of-function and loss-of-function PIK3R1 phenotypes.

A single center experience on PI3K/AKT/MTOR signaling defects: Towards pathogenicity assessment for four novel defects

BACKGROUND

Phosphoinositide 3 kinases (PI3K) are lipid kinases expressed in lymphocytes/myeloid cells. PI3K/AKT/mTOR signaling defects present with recurrent infections, autoimmunity, lymphoproliferation, and agammaglobulinemia.

OBJECTIVE

To characterize the PI3K/AKT/mTOR pathway defects and perform pathway analyses to assess novel variant pathogenicity.

METHODS

We included 12 patients (heterozygous PIK3CD (n = 9) and PIK3R1 (n = 1) (activated PI3K delta syndrome (APDS) with gain-of-function mutations) and homozygous PIK3R1 variant (n = 2)), performed clinical/laboratory/genetic evaluation, and flow cytometric PI3K/AKT/mTOR pathway analyses.

RESULTS

Median age at onset of complaints was 17.5 months (3 months to 12 years) and at diagnosis was 15.7 years (2.5-37) in APDS. Median diagnostic delay was 12.9 years (1.6-27). Recurrent respiratory tract infections (90%), lymphoproliferation (70%), autoimmune/inflammatory findings (60%), and allergy (40%) were common in APDS. Recurrent viral infections were present in 4/10 and malignancy (non-Hodgkin lymphoma and testicular yolk sac tumor) was present in 2/10 in APDS. Low CD4+ T cells(5/8) with increased CD4+ effector memory (8/8) and CD4+ TEMRA cells (6/8) were present in the given number of APDS patients. We diagnosed tubulointerstitial nephritis, Langerhans cell histiocytosis, and late-onset congenital adrenal hyperplasia in APDS. Allergic findings, lymphoproliferation/malignancy, and high IgM were present in the APDS but not in PIK3R1 deficiency. Low IgM/IgG/CD19+ B cell counts were characteristic in patients with PIK3R1 homozygous loss-of function mutations.

CONCLUSION

Differential diagnosis with combined immunodeficiency and diseases of immune dysregulation make molecular genetic analysis crucial for diagnosing mTOR pathway defects. It is easy to differentiate APDS and homozygous PIK3R1 defects with specific laboratory features. Additionally, mTOR pathway functional analysis is a definitive diagnostic and pathogenicity assessment tool for novel APDS mutations.

Genetic Characteristics of a Large Pediatric Cohort of Patients with Inborn Errors of Immunity: Single-Center Experience

More than 450 genetic defects result in inborn errors of immunity (IEI). Their individual prevalence in specific cohorts is influenced by national characteristics and other factors. We present results of genetic testing conducted in 1809 Russian children with IEI. Genetic defects confirming IEI were found in 1112 out of 1809 (61.5%) probands. These defects included variants in 118 single genes (87.9% of patients) and aberrations in 6 chromosomes (11.8%). Notably, three patients harbored pathogenic variants in more than one IEI gene. Large deletions constituted 5% of all defects. Out of the 799 original variants, 350 (44%) have not been described previously. Rare genetic defects (10 or fewer patients per gene) were identified in 20% of the patients. Among 967 probands with germline variants, defects were inherited in an autosomal dominant manner in 29%, X-linked in 34%, and autosomal recessive in 37%. Four females with non-random X-inactivation exhibited symptoms of X-linked diseases (BTK, WAS, CYBB, IKBKG gene defects). Despite a relatively low rate of consanguinity in Russia, 47.9% of autosomal recessive gene defects were found in a homozygous state. Notably, 28% of these cases carried "Slavic" mutation of the NBN gene or known hot-spot mutations in other genes. The diversity of IEI genetic forms and the high frequency of newly described variants underscore the genetic heterogeneity within the Russian IEI group. The new variants identified in this extensive cohort will enrich genetic databases.

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.

Monogenic Inborn Errors of Immunity with impaired IgG response to polysaccharide antigens but normal IgG levels and normal IgG response to protein antigens

In patients with severe and recurrent infections, minimal diagnostic workup to test for Inborn Errors of Immunity (IEI) includes a full blood count, IgG, IgA and IgM. Vaccine antibodies against tetanus toxoid are also frequently measured, whereas testing for anti-polysaccharide IgG antibodies and IgG subclasses is not routinely performed by primary care physicians. This basic approach may cause a significant delay in diagnosing monogenic IEI that can present with an impaired IgG response to polysaccharide antigens with or without IgG subclass deficiency at an early stage. Our article reviews genetically defined IEI, that may initially present with an impaired IgG response to polysaccharide antigens, but normal or only slightly decreased IgG levels and normal responses to protein or conjugate vaccine antigens. We summarize clinical, genetic, and immunological findings characteristic for these IEI. This review may help clinicians to identify patients that require extended immunologic and genetic evaluations despite unremarkable basic immunologic findings. We recommend the inclusion of anti-polysaccharide IgG antibodies as part of the initial routine work-up for possible IEI.

A qualitative study to explore the burden of disease in activated phosphoinositide 3-kinase delta syndrome (APDS)

BACKGROUND

Activated phosphoinositide 3-kinase delta syndrome (APDS) is an ultra-rare primary immunodeficiency, with only 256 cases reported globally. This study aimed to explore the disease burden of APDS from the perspective of individuals with APDS and their caregivers.

METHODS

Qualitative interviews were conducted with healthcare providers (HCPs), individuals with APDS and caregivers, to explore the symptoms and health-related quality of life (HRQoL) impact of APDS. Some individuals and caregivers also completed a narrative account exercise. All interviews were audio recorded and transcribed. Data were analysed using thematic analysis and saturation was recorded.

RESULTS

Semi-structured qualitative interviews were conducted with healthcare providers (HCPs), individuals with APDS and caregivers. Individuals and caregivers had the option of completing a narrative account exercise. Six HCPs participated in an interview. Seven participants completed the narrative account exercise (N = 5 caregivers and N = 2 individuals with APDS) and 12 took part in an interview (N = 4 caregivers and N = 8 individuals with APDS). Themes identified from HCPs interviews included symptoms, clinical manifestations, HRQoL impacts and treatments/management of APDS. The narrative account exercise identified similar themes, but with the addition to the journey to diagnosis. These themes were explored during the individual/caregiver interviews. Reported clinical manifestations and symptoms of APDS included susceptibility to infections, lymphoproliferation, gastrointestinal (GI) disorders, fatigue, bodily pain, and breathing difficulties. HRQoL impacts of living with APDS included negative impacts to daily activities, including work, education and social and leisure activities, physical functioning, as well as emotional well-being, such as concern for the future, and interpersonal relationships. Impacts to caregiver HRQoL included negative impacts to physical health, work, emotional well-being, interpersonal relationships and family life and holidays. The management of APDS included the use of healthcare services and medications including immunoglobulin replacement therapy (IRT), rapamycin, prophylactic antibiotics, leniolisib, as well as medical procedures due to complications.

CONCLUSIONS

APDS has a high disease burden and there is an unmet need for licensed, more targeted treatments which modify disease progression. This study was the first to describe the day-to-day experience and HRQoL impact of APDS from the perspective of individuals living with the condition, caregivers and treating physicians.

The Etiologic Landscape of Lymphoproliferation in Childhood: Proposal for a Diagnostic Approach Exploring from Infections to Inborn Errors of Immunity and Metabolic Diseases

Lymphoproliferation is defined by lymphadenopathy, splenomegaly, hepatomegaly, or lymphocytic organ and tissue infiltration. The most common etiologies of lymphoproliferation are represented by infectious diseases and lymphoid malignancies. However, it is increasingly recognized that lymphoproliferative features can be the presenting sign of rare conditions, including inborn errors of immunity (IEI) and inborn errors of metabolism (IEM). Among IEI, lymphoproliferation is frequently observed in autoimmune lymphoproliferative syndrome (ALPS) and related disorders, common variable immunodeficiency (CVID), activated phosphoinositide 3-kinase δ syndrome, and Epstein-Barr virus (EBV)-related disorders. Gaucher disease and Niemann-Pick disease are the most common IEMs that can present with isolated lymphoproliferative features. Notably, other rare conditions, such as sarcoidosis, Castleman disease, systemic autoimmune diseases, and autoinflammatory disorders, should be considered in the differential diagnosis of patients with persistent lymphoproliferation when infectious and malignant diseases have been reasonably ruled out. The clinical features of lymphoproliferative diseases, as well as the associated clinical findings and data deriving from imaging and first-level laboratory investigations, could significantly help in providing the correct diagnostic suspicion for the underlying etiology. This paper reviews the most relevant diseases associated with lymphoproliferation, including infectious diseases, hematological malignancies, IEI, and IEM. Moreover, some practical indications to orient the initial diagnostic process are provided, and two diagnostic algorithms are proposed for the first-level assessment and the approach to persistent lymphoproliferation, respectively.

[Activated phosphoinositide 3-kinase delta syndrome: report of seven cases]

OBJECTIVES

To summarize the clinical data of 7 children with activated phosphoinositide 3-kinase delta syndrome (APDS) and enhance understanding of the disease.

METHODS

A retrospective analysis was conducted on clinical data of 7 APDS children admitted to Hunan Provincial People's Hospital from January 2019 to August 2023.

RESULTS

Among the 7 children (4 males, 3 females), the median age of onset was 30 months, and the median age at diagnosis was 101 months. Recurrent respiratory tract infections, hepatosplenomegaly, and multiple lymphadenopathy were observed in all 7 cases. Sepsis was observed in 5 cases, otitis media and multiple caries were observed in 3 cases, and diarrhea and joint pain were observed in 2 cases. Lymphoma and systemic lupus erythematosus were observed in 1 case each. Fiberoptic bronchoscopy was performed in 4 cases, revealing scattered nodular protrusions in the bronchial lumen. The most common respiratory pathogen was Streptococcus pneumoniae (4 cases). Six patients had a p.E1021K missense mutation, and one had a p.434-475del splice site mutation.

CONCLUSIONS

p.E1021K is the most common mutation site in APDS children. Children who present with one or more of the following symptoms: recurrent respiratory tract infections, hepatosplenomegaly, multiple lymphadenopathy, otitis media, and caries, and exhibit scattered nodular protrusions on fiberoptic bronchoscopy, should be vigilant for APDS. Citation:Chinese Journal of Contemporary Pediatrics, 2024, 26(5): 499-505.

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.

Phenotypic and Immunological Characterization of Patients with Activated PI3Kδ Syndrome 1 Presenting with Autoimmunity

PURPOSE

Autoimmunity is a significant feature of APDS1 patients. We aimed to explore the pathogenic immune phenotype and possible mechanisms of autoimmunity in APDS1 patients.

METHODS

The clinical records and laboratory data of 42 APDS1 patients were reviewed. Immunophenotypes were evaluated by multiparametric flow cytometry. Autoantibodies were detected via antigen microarray analysis.

RESULTS

A total of 42 children with PIK3CD gene mutations were enrolled. Immunological tests revealed increased proportions of effector memory cells (86%) and central memory cells (59%) among CD4+ T cells; increased proportions of effector memory cells (83%) and terminally differentiated effector memory T cells (38%) among CD8+ T cells. Fewer CD3+ T cells and B cells and higher IgG levels were reported in patients with autoimmunity. The proportion of Tregs was decreased, and the proportions of Th9, Tfh, and Tfr cells were increased in APDS1 patients. Among APDS1 patients, higher proportion of Th2 and Tfr cells were found in those with autoimmunity. The proportions of CD11c+ B and CD21lo B cells in patients with autoimmunity were significantly increased. Antigen microarray analysis revealed a wide range of IgG/IgM autoantibodies in patients with APDS1. In patients with autoimmunity, the proportion of Tfr might be positively correlated with autoantibodies.

CONCLUSIONS

The pathogenic immune phenotype of APDS1 patients included (1) deceased CD3+ T-cell and B-cell counts and increased IgG levels in patients with autoimmunity, (2) an imbalanced T helper cell subset, (3) increased proportions of autoreactive B cells, and (4) distinct autoantibody reactivities in patients with autoimmunity.

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.

Leniolisib: a novel treatment for activated phosphoinositide-3 kinase delta syndrome

IC50 = 11 nM (PI3Kδ); 244 nM (PI3Kα); 424 nM (PI3Kβ), 2,230 nM (PI3Kγ).

Systematic review of mortality and survival rates for APDS

Activated phosphoinositide 3-kinase delta syndrome (APDS) is a rare genetic disorder that presents clinically as a primary immunodeficiency. Clinical presentation of APDS includes severe, recurrent infections, lymphoproliferation, lymphoma, and other cancers, autoimmunity and enteropathy. Autosomal dominant variants in two independent genes have been demonstrated to cause APDS. Pathogenic variants in PIK3CD and PIK3R1, both of which encode components of the PI3-kinase, have been identified in subjects with APDS. APDS1 is caused by gain of function variants in the PIK3CD gene, while loss of function variants in PIK3R1 have been reported to cause APDS2. We conducted a review of the medical literature and identified 256 individuals who had a molecular diagnosis for APDS as well as age at last report; 193 individuals with APDS1 and 63 with APDS2. Despite available treatments, survival for individuals with APDS appears to be shortened from the average lifespan. A Kaplan-Meier survival analysis for APDS showed the conditional survival rate at the age of 20 years was 87%, age of 30 years was 74%, and ages of 40 and 50 years were 68%. Review of causes of death showed that the most common cause of death was lymphoma, followed by complications from HSCT. The overall mortality rate for HSCT in APDS1 and APDS2 cases was 15.6%, while the mortality rate for lymphoma was 47.6%. This survival and mortality data illustrate that new treatments are needed to mitigate the risk of death from lymphoma and other cancers as well as infection. These analyses based on real-world evidence gathered from the medical literature comprise the largest study of survival and mortality for APDS to date.

Genetics and clinical phenotypes in common variable immunodeficiency

Common variable immunodeficiency (CVID) is one of the most common symptomatic groups of inborn errors of immunity. In addition to infections resulting from insufficient levels of immune globulins and antibodies, many patients develop inflammatory or autoimmune conditions, which are associated with increased mortality. This aspect of CVID has been the focus of many studies, and dissecting the clinical phenotypes of CVID, has had the goal of providing biomarkers to identify these subjects, potentially at the time of diagnosis. With the application of whole exome (WES) and whole genome analyses, an increasing number of monogenic causes of CVID have been elucidated. From the standpoint of the practicing physician, an important question is whether the clinical phenotype, particularly the occurrence of autoinflammation of autoimmunity, might suggest the likelihood of identifying a causative mutation, and if possible the gene most likely to underlie CVID. We addressed this question in a patient group of 405 subjects diagnosed with CVID from one medical center.

PI3Kδ Pathway Dysregulation and Unique Features of Its Inhibition by Leniolisib in Activated PI3Kδ Syndrome and Beyond

The phosphoinositide 3-kinase (PI3K) pathway regulates diverse cellular processes, with finely tuned PI3Kδ activity being crucial for immune cell development and function. Genetic hyperactivation of PI3Kδ causes the inborn error of immunity activated phosphoinositide 3-kinase δ syndrome (APDS). Several PI3Kδ inhibitors have been investigated as treatment options for APDS, but only leniolisib has shown both efficacy and tolerability. In contrast, severe immune-mediated adverse events such as colitis, neutropenia, and hepatotoxicity have been observed with other PI3Kδ inhibitors, particularly those indicated for hematological malignancies. We propose that leniolisib is distinguished from other PI3Kδ inhibitors due to its structure, specific inhibitory properties selectively targeting the δ isoform without overinhibition of the δ or γ isoforms, and the precise match between APDS mechanism of disease and drug mechanism of action.

Interim analysis: Open-label extension study of leniolisib for patients with APDS

BACKGROUND

Activated phosphoinositide 3-kinase delta (PI3Kδ) syndrome (APDS; or p110δ-activating mutations causing senescent T cells, lymphadenopathy, and immunodeficiency) is an inborn error of immunity caused by PI3Kδ hyperactivity. Resultant immune deficiency and dysregulation lead to recurrent sinopulmonary infections, herpes viremia, autoimmunity, and lymphoproliferation.

OBJECTIVE

Leniolisib, a selective PI3Kδ inhibitor, demonstrated favorable impact on immune cell subsets and lymphoproliferation over placebo in patients with APDS over 12 weeks. Here, we report results from an interim analysis of an ongoing open-label, single-arm extension study.

METHODS

Patients with APDS aged 12 years or older who completed NCT02435173 or had previous exposure to PI3Kδ inhibitors were eligible. The primary end point was safety, assessed via investigator-reported adverse events (AEs) and clinical/laboratory evaluations. Secondary and exploratory end points included health-related quality of life, inflammatory markers, frequency of infections, and lymphoproliferation.

RESULTS

Between September 2016 and August 2021, 37 patients (median age, 20 years; 42.3% female) were enrolled. Of these 37 patients, 26, 9, and 2 patients had previously received leniolisib, placebo, or other PI3Kδ inhibitors, respectively. At the data cutoff date (December 13, 2021), median leniolisib exposure was 102 weeks. Overall, 32 patients (87%) experienced an AE. Most AEs were grades 1 to 3; none were grade 4. One patient with severe baseline comorbidities experienced a grade 5 AE, determined as unrelated to leniolisib treatment. While on leniolisib, patients had reduced annualized infection rates (P = .004), and reductions in immunoglobulin replacement therapy occurred in 10 of 27 patients. Other observations include reduced lymphadenopathy and splenomegaly, improved cytopenias, and normalized lymphocyte subsets.

CONCLUSIONS

Leniolisib was well tolerated and maintained durable outcomes with up to 5 years of exposure in 37 patients with APDS.

CLINICALTRIALS

gov identifier: NCT02859727.

Monogenic forms of common variable immunodeficiency and implications on target therapeutic approaches

PURPOSE OF REVIEW

Common variable immunodeficiency (CVID) is the most common symptomatic inborn error of immunity. The disorder is characterized by variable clinical and immunological manifestations, and, in a small minority of patients, a monogenic cause may be identified. In this review, we focalized on three different monogenic forms of CVID-like disease.

RECENT FINDINGS

Activated phosphoinositide 3-kinase delta syndrome (APDS) is a rare disorder characterized by hyperactivated class I phosphatidylinositol-3 kinase (PI3K) pathway. Affected patients present with respiratory infectious episodes, impaired viral clearance and lymphoproliferation. Recently, a direct PI3K inhibitor has been approved and it showed encouraging results both in controlling clinical and immunological manifestations of the disease. On the other hand, patients with defects in CTLA-4 or LRBA gene present with life-threatening immune dysregulation, autoimmunity and lymphocytic infiltration of multiple organs. Abatacept, a soluble cytotoxic T lymphocyte antigen 4 (CTLA-4) fusion protein that acts as a costimulation modulator, has been widely implemented for affected patients with good results as bridge treatment.

SUMMARY

Understanding the biological basis of CVID is important not only for enriching our knowledge of the human immune system, but also for setting the basis for potential targeted treatments in this disorder.

Changes in Treg and Breg cells in a healthy pediatric population

The interpretation of clinical diagnostic results in suspected inborn errors of immunity, including Tregopathies, is hampered by the lack of age-stratified reference values for regulatory T cells (Treg) in the pediatric population and a consensus on which Treg immunophenotype to use. Regulatory B cells (Breg) are an important component of the regulatory system that have been poorly studied in the pediatric population. We analyzed (1) the correlation between the three immunophenotypic definitions of Treg (CD4+CD25hiCD127low, CD4+CD25hiCD127lowFoxP3+, CD4+CD25hiFoxP3+), and with CD4+CD25hi and (2) the changes in Treg and Breg frequencies and their maturation status with age. We performed peripheral blood immunophenotyping of Treg and Breg (CD19+CD24hiCD38hi) by flow cytometry in 55 healthy pediatric controls. We observed that Treg numbers varied depending on the definition used, and the frequency ranged between 3.3-9.7% for CD4+CD25hiCD127low, 0.07-1.6% for CD4+CD25hiCD127lowFoxP3+, and 0.24-2.83% for CD4+CD25hiFoxP3+. The correlation between the three definitions of Treg was positive for most age ranges, especially between the two intracellular panels and with CD4+CD25hi vs CD4+CD25hiCD127low. Treg and Breg frequencies tended to decline after 7 and 3 years onwards, respectively. Treg's maturation status increased with age, with a decline of naïve Treg and an increase in memory/effector Treg from age 7 onwards. Memory Breg increased progressively from age 3 onwards. In conclusion, the number of Treg frequencies spans a wide range depending on the immunophenotypic definition used despite a good level of correlation exists between them. The decline in numbers and maturation process with age occurs earlier in Breg than in Treg.

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.

Future Directions in the Diagnosis and Treatment of APDS and IEI: a Survey of German IEI Centers

Introduction

The diagnosis and treatment of inborn errors of immunity (IEI) is a major challenge as the individual conditions are rare and often characterized by a variety of symptoms, which are often non disease-specific. Ideally, patients are treated in dedicated centers by physicians who specialize in the management of primary immune disorders. In this study, we used the example of Activated PI3Kδ syndrome (APDS), a rare IEI with an estimated prevalence of 1:1,000,000. We conducted surveys by questionnaire and interviewed physicians at different IEI centers in Germany.

Methods

We queried structural aspects of IEI care in Germany, diagnostic procedures in IEI care (including molecular diagnostics), distribution of APDS patients, APDS symptoms and severity, treatment algorithms in APDS, the role of stem cell transplantation and targeted therapies in IEI with focus on APDS. We were especially interested in how genetic diagnostics may influence treatment decisions, e.g. with regard to targeted therapies.

Results/discussion

Most centers care for both pediatric and adult patients. A total of 28 APDS patients are currently being treated at the centers we surveyed. Patient journeys vary considerably, as does severity of disease. Genetic diagnosis continues to gain importance - whole genome sequencing is likely to become routine in IEI in the next few years. According to the experts interviewed, stem cell transplantation and - with new molecules being approved - targeted therapies, will gain in importance for the treatment of APDS and IEI in general.

Activated phosphoinositide 3-kinase δ syndrome: Update from the ESID Registry and comparison with other autoimmune-lymphoproliferative inborn errors of immunity

BACKGROUND

Activated phosphoinositide-3-kinase δ syndrome (APDS) is an inborn error of immunity (IEI) with infection susceptibility and immune dysregulation, clinically overlapping with other conditions. Management depends on disease evolution, but predictors of severe disease are lacking.

OBJECTIVES

This study sought to report the extended spectrum of disease manifestations in APDS1 versus APDS2; compare these to CTLA4 deficiency, NFKB1 deficiency, and STAT3 gain-of-function (GOF) disease; and identify predictors of severity in APDS.

METHODS

Data was collected from the ESID (European Society for Immunodeficiencies)-APDS registry and was compared with published cohorts of the other IEIs.

RESULTS

The analysis of 170 patients with APDS outlines high penetrance and early onset of APDS compared to the other IEIs. The large clinical heterogeneity even in individuals with the same PIK3CD variant E1021K illustrates how poorly the genotype predicts the disease phenotype and course. The high clinical overlap between APDS and the other investigated IEIs suggests relevant pathophysiological convergence of the affected pathways. Preferentially affected organ systems indicate specific pathophysiology: bronchiectasis is typical of APDS1; interstitial lung disease and enteropathy are more common in STAT3 GOF and CTLA4 deficiency. Endocrinopathies are most frequent in STAT3 GOF, but growth impairment is also common, particularly in APDS2. Early clinical presentation is a risk factor for severe disease in APDS.

CONCLUSIONS

APDS illustrates how a single genetic variant can result in a diverse autoimmune-lymphoproliferative phenotype. Overlap with other IEIs is substantial. Some specific features distinguish APDS1 from APDS2. Early onset is a risk factor for severe disease course calling for specific treatment studies in younger patients.

The dysfunction of Tfh cells promotes pediatric recurrent respiratory tract infections development by interfering humoral immune responses

Recurrent respiratory tract infections (RRTIs) are one of the most common pediatric diseases. Although the pathogenesis of pediatric RRTIs remains unknown, ineffective B cell-dominated humoral immunity has been considered as the core mechanism. During the course of pediatric RRTIs, B cell-dominated humoral immunity has changed from "protector" of respiratory system to "bystander" of respiratory tract infections. Under physiological condition, Tfh cells are essential for B cell-dominated humoral immunity, including regulating GC formation, promoting memory B cell (MB)/plasma cell (PC) differentiation, inducting immunoglobulin (Ig) class switching, and selecting affinity-matured antibodies. However, in disease states, Tfh cells are dysfunctional, which can be reflected by phenotypes and cytokine production. Tfh cell dysfunctions can cause the disorders of B cell-dominated humoral immunity, such as promoting B cell presented apoptosis, abrogating total Ig production, reducing MB/PC populations, and delaying affinity maturation of antigens-specific antibodies. In this review, we focused on the functions of B and Tfh cells in the homeostasis of respiratory system, and specifically discussed the disorders of humoral immunity and aberrant Tfh cell responses in the disease process of pediatric RRTIs. We hoped to provide some clues for the prevention and treatment of pediatric RRTIs.

Two cases of successful sirolimus treatment for patients with activated phosphoinositide 3-kinase δ syndrome 1

BACKGROUND

Activated phosphoinositide3-kinase (PI3K) δ syndrome 1 (APDS1) is a novel inborn errors of immunity (IEIs) caused by heterozygous gain of function mutations in PI3Kδ catalytic p110δ (PIK3CD). APDS1 has a spectrum of clinical manifestations. Recurrent respiratory infections, lymphoproliferation, hepatosplenomegaly, hyper-IgM syndrome and autoimmunity are the common symptoms of this disease.

CASE PRESENTATION

Patient 1 presented with recurrent respiratory infections, hepatosplenomegaly and hyper-IgM syndrome. Patient 2 developed early onset systemic lupus erythematosus (SLE)-like disease with resistant thrombocytopenia. c.3061 G > A and c.2314G > A variants in the PIK3CD gene were detected by whole exome sequencing in two patients respectively. c.2314G > A variant in PIK3CD gene of patient 2 is a newly report. After genetic diagnosis, two patients received sirolimus treatment and sirolimus alleviated clinical manifestations, including hepatosplenomegaly in patient 1 and thrombocytopenia in patient 2.

CONCLUSION

Genetics diagnosis should be considered in patients with complicated clinical manifestations with no or insufficient response to the conventional therapies. If whole exome sequencing suggests a variant in PIK3CD gene, sirolimus may relieve hepatosplenomegaly and resistant thrombocytopenia. This is the first report of c.2314G > A variant in PIK3CD gene.

Autoimmune lymphoproliferative immunodeficiencies (ALPID) in childhood: breakdown of immune homeostasis and immune dysregulation

Many inborn errors of immunity (IEI) manifest with hallmarks of both immunodeficiency and immune dysregulation due to uncontrolled immune responses and impaired immune homeostasis. A subgroup of these disorders frequently presents with autoimmunity and lymphoproliferation (ALPID phenotype). After the initial description of the genetic basis of autoimmune lymphoproliferative syndrome (ALPS) more than 20 years ago, progress in genetics has helped to identify many more genetic conditions underlying this ALPID phenotype. Among these, the majority is caused by a group of autosomal-dominant conditions including CTLA-4 haploinsufficiency, STAT3 gain-of-function disease, activated PI3 kinase syndrome, and NF-κB1 haploinsufficiency. Even within a defined genetic condition, ALPID patients may present with staggering clinical heterogeneity, which makes diagnosis and management a challenge. In this review, we discuss the pathophysiology, clinical presentation, approaches to diagnosis, and conventional as well as targeted therapy of the most common ALPID conditions.

Activated PI3Kδ syndrome - reviewing challenges in diagnosis and treatment

Activated PI3Kδ syndrome (APDS) is a rare inborn error of immunity (IEI) characterized primarily by frequent infections, lymphoproliferation and autoimmunity. Since its initial description in 2013, APDS has become part of the growing group of nearly 500 IEIs affecting various components of the immune system. The two subtypes of APDS - APDS1 and APDS2 - are caused by variants in the PIK3CD and PIK3R1 genes, respectively. Due to the rarity of the disease and the heterogeneous clinical picture, many patients are not diagnosed until years after symptom onset. Another challenge is the large number of PIK3CD and PIK3R1 variants whose functional significance for developing APDS is inconclusive. Treatment of APDS has so far been mostly symptom-oriented with immunoglobulin replacement therapy, immunosuppressive therapies and antibiotic or antiviral prophylaxes. Additionally, allogeneic stem cell transplantation as well as new targeted therapies are options targeting the root cause that may improve patients' quality of life and life expectancy. However, the clinical course of the disease is difficult to predict which complicates the choice of appropriate therapies. This review article discusses diagnostic procedures and current and future treatment options, and highlights the difficulties that physicians, patients and their caretakers face in managing this complex disease. This article is based on cohort studies, the German and US guidelines on the management of primary immunodeficiencies as well as on published experience with diagnosis and compiled treatment experience for APDS.

Epstein-Barr virus-associated B-cell lymphoproliferative disorder meeting the definition of CAEBV B cell disease: a case report

BACKGROUND

Chronic active Epstein-Barr virus infection (CAEBV) is a systemic EBV-positive lymphoproliferative disorder (EBV-LPD) considered to be associated with a genetic immunological abnormality, although its cause is still unclear. EBV is usually detected in T cells or NK cells in CAEBV patients with only a few cases involving B cells described in East Asia, which may be due to differences in genetic and environmental factors.

CASE DESCRIPTION

A 16-year-old boy who seemed to be diagnosed as CAEBV of B cell type was studied. The patient had IM-like symptoms persisting for more than 3 months, high levels of EBV DNA in the PB, and positive EBER in situ hybridization in B cells. In addition, to exclude underlying genetic disorders, we performed next-generation sequencing (NGS) and whole-exome sequencing (WES), which identified the missense mutation in PIK3CD (E1021K), ADA (S85L) and CD3D (Q140K) in the patient while no same genetic mutation was detected in his parents and sister. However, there is no diagnosis of CAEBV of B cell type in the most recent World Health Organization classification of tumors of hematopoietic and lymphoid tissues, therefore we finally diagnosed this patient as EBV-B-LPD.

CONCLUSIONS

This study shows a rare case of a patient meeting the definition of CAEBV B-cell disease in East Asia. Meanwhile, the case indicates that the missense mutation and the disease are related.

Phosphatidylinositol 3 kinase inhibitor-related pneumonitis: a systematic review and meta-analysis

INTRODUCTION

Serious phosphatidylinositol 3 kinase (PI3K) inhibitor-related pneumonitis has raised clinical concerns, and integrated data for this condition are lacking.

METHODS

Randomized controlled trials (RCTs) comparing PI3K inhibitor therapy with control treatments from electronic databases and registrations were searched from inception to 1 April 20231 April 2023seven1 April 2023. The outcomes of our study were the incidence and risk of all-grade and grade ≥ 3 PI3K inhibitor-associated pneumonitis compared with controls.

RESULTS

The meta-analysis included 13 studies comprising 3916 patients. The incidence of all-grade and grade ≥ 3 pneumonitis was 3.7% (82/2210) and 3.0% (35/1162) in patients treated with PI3K inhibitors. PI3K inhibitors significantly increased the risk of all-grade and grade ≥ 3 pneumonitis compared with controls (RR 5.63, 95% CI [2.97, 10.65], P < 0.00001; RR 6.85, 95% CI [2.45, 19.11], P = 0.0002, respectively) with no significant heterogeneity across studies. In terms of different PI3K inhibitors, copanlisib and idelalisib significantly increased the risk of pneumonitis compared to controls (RR 4.99, 95% CI [1.19, 21.01], P = 0.03; RR 5.53, 95% CI [2.35, 13.01], P < 0.0001, respectively).

CONCLUSION

PI3K inhibitors significantly increased the risk of pneumonitis compared with controls, and most cases are severe or even life-threatening.

PROSPERO REGISTRATION NUMBER

CRD42022318878.

Human PIK3R1 mutations disrupt lymphocyte differentiation to cause activated PI3Kδ syndrome 2

Heterozygous loss-of-function (LOF) mutations in PIK3R1 (encoding phosphatidylinositol 3-kinase [PI3K] regulatory subunits) cause activated PI3Kδ syndrome 2 (APDS2), which has a similar clinical profile to APDS1, caused by heterozygous gain-of-function (GOF) mutations in PIK3CD (encoding the PI3K p110δ catalytic subunit). While several studies have established how PIK3CD GOF leads to immune dysregulation, less is known about how PIK3R1 LOF mutations alter cellular function. By studying a novel CRISPR/Cas9 mouse model and patients' immune cells, we determined how PIK3R1 LOF alters cellular function. We observed some overlap in cellular defects in APDS1 and APDS2, including decreased intrinsic B cell class switching and defective Tfh cell function. However, we also identified unique APDS2 phenotypes including defective expansion and affinity maturation of Pik3r1 LOF B cells following immunization, and decreased survival of Pik3r1 LOF pups. Further, we observed clear differences in the way Pik3r1 LOF and Pik3cd GOF altered signaling. Together these results demonstrate crucial differences between these two genetic etiologies.

ANCA vasculitis expands the spectrum of autoimmune manifestations of activated PI3 kinase δ syndrome

Activated phosphoinositide 3-kinase δ syndrome (APDS) is a combined immunodeficiency with a broad clinical phenotype, including not only an increased propensity for sinopulmonary and herpesviruses infections but also immune dysregulation, such as benign lymphoproliferation, autoimmunity, and malignancy. Autoimmune complications are increasingly recognized as initial presenting features of immune dysregulation in inborn errors of immunity (IEIs), including APDS, so awareness of the spectrum of autoimmune features inherit within these disorders is critical. We present here a patient vignette to highlight cutaneous antineutrophil cytoplasmic antibody (ANCA) vasculitis as an underrecognized autoimmune manifestation of APDS. The genetic defects underlying APDS result in increased PI3Kδ signaling with aberrant downstream signaling pathways and loss of B- and/or T-cell immunologic tolerance mechanisms, which promote the development of autoimmunity. An understanding of the molecular pathways and mechanisms that lead to immune dysregulation in APDS has allowed for significant advancements in the development of precision-medicine therapeutics, such as leniolisib, to reduce the morbidity and mortality for these patients. Overall, this case and review highlight the need to maintain a high index of suspicion for IEIs, such as APDS, in those presenting with autoimmunity in combination with a dysregulated immune phenotype for prompt diagnosis and targeted intervention.

Successful haploidentical hematopoietic stem cell transplantation for activated phosphoinositide 3-kinase δ syndrome: Case report and literature review

RATIONALE

Activated phosphoinositide 3-kinase δ syndrome (APDS), a recently described primary immunodeficiency,is caused by autosomal dominant mutation in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta(PIK3CD) gene encoding the p110δ catalytic subunit of PI3Kδ (APDS1) or the PIK3R1 gene that encodes the p85α regulatory subunit of PI3Kδ (APDS2). Gain-of-function mutation of PIK3CD in APDS1 leads to p110δ hyperactivity, with the result of the hyperphosphorylation of downstream mediators of Akt and mammalian target of rapamycin that cause a series of clinical symptoms. Few cases with APDS were reported in Asia.

PATIENT CONCERNS

We report a 6-year-old patient with a recurrent respiratory infection, cryptosporidium enteritis, lymphoproliferation, high serum immunoglobulin-M level, anemia, and inverted CD4+/CD8+ ratio. The whole exome sequencing confirmed a heterozygous missense mutation c.3061G>A（p.E1021K）in patient and her mother. Her mutant gene is inherited from her mother, but her mother has not any clinical symptoms.

DIAGNOSES

Activated phosphoinositide 3-kinase δ syndrome.

INTERVENTIONS

The patient was received immunoglobulin (Ig) replacement therapy, antibiotics, and rapamycin treatment. Through effectively controlling infection and optimal timing of transplantation by adjusting the conditioning regimen, haploidentical Hematopoietic Stem Cell Transplantation(haplo-HSCT) from her brother was successfully performed.

OUTCOMES

The patient is in good condiion with a good quality of life after 20 months of follow-up.

LESSONS

We reported a rare APDS1 case with PIK3CD E1021K gene mutation, Successfully treated with haplo-HSCT. This case provided a reference for treating APDS with haplo-HSCT.

Novel mutation of SLC37A4 in a glycogen storage disease type Ib patient with neutropenia, horseshoe kidney, and arteriovenous malformation: a case report

Glycogen storage disease type Ib (GSDIb) is an autosomal recessive disorder caused by mutations of SLC37A4 gene, which encodes glucose 6-phosphate translocase (G6PT). Malfunction of G6PT leads to excessive fat and glycogen in liver, kidney, and intestinal mucosa. The clinical manifestations of GSD1b include hepatomegaly, renomegaly, neutropenia, hypoglycemia, and lactic acidosis. Furthermore, the disorder may result in severe complications in long-term including inflammatory bowel disease (IBD), hepatocellular adenomas (HCA), short stature, and autoimmune disorders, which stem from neutropenia and neutrophil dysfunction. Here, we represent a novel mutation of SLC37A4 in a 5-month girl who has a history of hospitalizations several times due to recurrent infection and her early presentations were failure to thrive and tachypnea. Further investigations revealed mild atrial septal defect, mild arteriovenous malformation from left lung, esophageal reflux, Horseshoe kidney, and urinary reflux in this patient. Moreover, the lab tests showed neutropenia, immunoglobulin (Ig) G and IgA deficiency, as well as thrombocytosis. Whole exome sequencing revealed c.1245G > A P.W415 homozygous mutation in SLC37A4 gene and c.580G > A p.V1941 heterozygous mutation in PIK3CD gene. This study shows that manifestations of GSD1b may not be limited to what was previously known and it should be considered in a wider range of patients.

Phosphatidyl Inositol 3-Kinase (PI3K)-Inhibitor CDZ173 protects against LPS-induced osteolysis

A major complication of a joint replacement is prosthesis loosening caused by inflammatory osteolysis, leading to the revision of the operation. This is due to the abnormal activation of osteoclast differentiation and function caused by periprosthetic infection. Therefore, targeting abnormally activated osteoclasts is still effective for treating osteolytic inflammatory diseases. CDZ173 is a selective PI3K inhibitor widely used in autoimmune-related diseases and inflammatory diseases and is currently under clinical development. However, the role and mechanism of CDZ173 in osteoclast-related bone metabolism remain unclear. The possibility for treating aseptic prosthesis loosening brought on by inflammatory osteolysis illness can be assessed using an LPS-induced mouse cranial calcium osteolysis model. In this study, we report for the first time that CDZ173 has a protective effect on LPS-induced osteolysis. The data show that this protective effect is due to CDZ173 inhibiting the activation of osteoclasts in vivo. Meanwhile, our result demonstrated that CDZ173 had a significant inhibitory effect on RANKL-induced osteoclasts. Furthermore, using the hydroxyapatite resorption pit assay and podosol actin belt staining, respectively, the inhibitory impact of CDZ173 on bone resorption and osteoclast fusion of pre-OC was determined. In addition, staining with alkaline phosphatase (ALP) and alizarin red (AR) revealed that CDZ173 had no effect on osteoblast development in vitro. Lastly, CDZ173 inhibited the differentiation and function of osteoclasts by weakening the signal axis of PI3K-AKT/MAPK-NFATc1 in osteoclasts. In conclusion, our results highlight the potential pharmacological role of CDZ173 in preventing osteoclast-mediated inflammatory osteolysis and its potential clinical application.

Role of protein phosphorylation in cell signaling, disease, and the intervention therapy

Protein phosphorylation is an important post-transcriptional modification involving an extremely wide range of intracellular signaling transduction pathways, making it an important therapeutic target for disease intervention. At present, numerous drugs targeting protein phosphorylation have been developed for the treatment of various diseases including malignant tumors, neurological diseases, infectious diseases, and immune diseases. In this review article, we analyzed 303 small-molecule protein phosphorylation kinase inhibitors (PKIs) registered and participated in clinical research obtained in a database named Protein Kinase Inhibitor Database (PKIDB), including 68 drugs approved by the Food and Drug Administration of the United States. Based on previous classifications of kinases, we divided these human protein phosphorylation kinases into eight groups and nearly 50 families, and delineated their main regulatory pathways, upstream and downstream targets. These groups include: protein kinase A, G, and C (AGC) and receptor guanylate cyclase (RGC) group, calmodulin-dependent protein kinase (CaMK) group, CMGC [Cyclin-dependent kinases (CDKs), Mitogen-activated protein kinases (MAPKs), Glycogen synthase kinases (GSKs), and Cdc2-like kinases (CLKs)] group, sterile (STE)-MAPKs group, tyrosine kinases (TK) group, tyrosine kinase-like (TKL) group, atypical group, and other groups. Different groups and families of inhibitors stimulate or inhibit others, forming an intricate molecular signaling regulatory network. This review takes newly developed new PKIs as breakthrough point, aiming to clarify the regulatory network and relationship of each pathway, as well as their roles in disease intervention, and provide a direction for future drug development.

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.

B- and T-Cell Subset Abnormalities in Monogenic Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is a heterogeneous group of inborn errors of immunity characterized by reduced serum concentrations of different immunoglobulin isotypes. CVID is the most prevalent symptomatic antibody deficiency with a broad range of infectious and non-infectious clinical manifestations. Various genetic and immunological defects are known to be involved in the pathogenesis of CVID. Monogenic defects account for the pathogenesis of about 20-50% of CVID patients, while a variety of cases do not have a defined genetic background. Deficiencies in molecules of B cell receptor signaling or other pathways involving B-cell development, activation, and proliferation could be associated with monogenetic defects of CVID. Genetic defects damping different B cell developmental stages can alter B- and even other lymphocytes’ differentiation and might be involved in the clinical and immunologic presentations of the disorder. Reports concerning T and B cell abnormalities have been published in CVID patients, but such comprehensive data on monogenic CVID patients is few and no review article exists to describe the abrogation of lymphocyte subsets in these disorders. Hence, we aimed to review the role of altered B- and T-cell differentiation in the pathogenesis of CVID patients with monogenic defects.

Genomic characterization of lymphomas in patients with inborn errors of immunity

Inborn errors of immunity-associated lymphomas are characterized by distinct clinical features and genetic signatures.

Both germline and somatic alterations contribute to lymphomagenesis in patients with inborn errors of immunity.

Patients with inborn errors of immunity (IEI) have a higher risk of developing cancer, especially lymphoma. However, the molecular basis for IEI-related lymphoma is complex and remains elusive. Here, we perform an in-depth analysis of lymphoma genomes derived from 23 IEI patients. We identified and validated disease-causing or -associated germline mutations in 14 of 23 patients involving ATM, BACH2, BLM, CD70, G6PD, NBN, PIK3CD, PTEN, and TNFRSF13B. Furthermore, we profiled somatic mutations in the lymphoma genome and identified 8 genes that were mutated at a significantly higher level in IEI-associated diffuse large B-cell lymphomas (DLBCLs) than in non-IEI DLBCLs, such as BRCA2, NCOR1, KLF2, FAS, CCND3, and BRWD3. The latter, BRWD3, is furthermore preferentially mutated in tumors of a subgroup of activated phosphoinositide 3-kinase δ syndrome patients. We also identified 5 genomic mutational signatures, including 2 DNA repair deficiency-related signatures, in IEI-associated lymphomas and a strikingly high number of inter- and intrachromosomal structural variants in the tumor genome of a Bloom syndrome patient. In summary, our comprehensive genomic characterization of lymphomas derived from patients with rare genetic disorders expands our understanding of lymphomagenesis and provides new insights for targeted therapy.

Pathogenesis of Autoimmune Cytopenias in Inborn Errors of Immunity Revealing Novel Therapeutic Targets

Autoimmune diseases are usually associated with environmental triggers and genetic predisposition. However, a few number of autoimmune diseases has a monogenic cause, mostly in children. These diseases may be the expression, isolated or associated with other symptoms, of an underlying inborn error of immunity (IEI). Autoimmune cytopenias (AICs), including immune thrombocytopenic purpura (ITP), autoimmune hemolytic anemia (AIHA), autoimmune neutropenia (AN), and Evans’ syndrome (ES) are common presentations of immunological diseases in the pediatric age, with at least 65% of cases of ES genetically determined. Autoimmune cytopenias in IEI have often a more severe, chronic, and relapsing course. Treatment refractoriness also characterizes autoimmune cytopenia with a monogenic cause, such as IEI. The mechanisms underlying autoimmune cytopenias in IEI include cellular or humoral autoimmunity, immune dysregulation in cases of hemophagocytosis or lymphoproliferation with or without splenic sequestration, bone marrow failure, myelodysplasia, or secondary myelosuppression. Genetic characterization of autoimmune cytopenias is of fundamental importance as an early diagnosis improves the outcome and allows the setting up of a targeted therapy, such as CTLA-4 IgG fusion protein (Abatacept), small molecule inhibitors (JAK-inhibitors), or gene therapy. Currently, gene therapy represents one of the most attractive targeted therapeutic approaches to treat selected inborn errors of immunity. Even in the absence of specific targeted therapies, however, whole exome genetic testing (WES) for children with chronic multilineage cytopenias should be considered as an early diagnostic tool for disease diagnosis and genetic counseling.

Activated Phosphoinositide 3-Kinase δ Syndrome: a Large Pediatric Cohort from a Single Center in China

PURPOSE

Activated phosphoinositide 3-kinase δ syndrome (APDS) is a primary immunodeficiency first described in 2013, which is caused by gain-of-function mutations in PIK3CD or PIK3R1, and characterized by recurrent respiratory tract infections, lymphoproliferation, herpesvirus infection, autoimmunity, and enteropathy. We sought to review the clinical phenotypes, immunological characteristics, treatment, and prognosis of APDS in a large genetically defined Chinese pediatric cohort.

METHODS

Clinical records, radiology examinations, and laboratory investigations of 40 APDS patients were reviewed. Patients were contacted via phone call to follow up their current situation.

RESULTS

Sinopulmonary infections and lymphoproliferation were the most common complications in this cohort. Three (10.3%) and five (12.5%) patients suffered localized BCG-induced granulomatous inflammation and tuberculosis infection, respectively. Twenty-seven patients (67.5%) were affected by autoimmunity, while malignancy (7.5%) was relatively rare to be seen. Most patients in our cohort took a combined treatment of anti-infection prophylaxis, immunoglobulin replacement, and immunosuppressive therapy such as glucocorticoid or rapamycin administration. Twelve patients underwent hematopoietic stem cell transplantation (HSCT) and had a satisfying prognosis.

CONCLUSION

Clinical spectrum of APDS is heterogeneous. This cohort's high incidence of localized BCG-induced granulomatous inflammation and tuberculosis indicates Mycobacterial susceptibility in APDS patients. Rapamycin is effective in improving lymphoproliferation and cytopenia. HSCT is an option for those who have severe complications and poor response to other treatments.

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.

Autoimmune Cytopenias and Dysregulated Immunophenotype Act as Warning Signs of Inborn Errors of Immunity: Results From a Prospective Study

Inborn errors of immunity (IEI) are genetic disorders characterized by a wide spectrum of clinical manifestations, ranging from increased susceptibility to infections to significant immune dysregulation. Among these, primary immune regulatory disorders (PIRDs) are mainly presenting with autoimmune manifestations, and autoimmune cytopenias (AICs) can be the first clinical sign. Significantly, AICs in patients with IEI often fail to respond to first-line therapy. In pediatric patients, autoimmune cytopenias can be red flags for IEI. However, for these cases precise indicators or parameters useful to suspect and screen for a hidden congenital immune defect are lacking. Therefore, we focused on chronic/refractory AIC patients to perform an extensive clinical evaluation and multiparametric flow cytometry analysis to select patients in whom PIRD was strongly suspected as candidates for genetic analysis. Key IEI-associated alterations causative of STAT3 GOF disease, IKAROS haploinsufficiency, activated PI3Kδ syndrome (APDS), Kabuki syndrome and autoimmune lymphoproliferative syndrome (ALPS) were identified. In this scenario, a dysregulated immunophenotype acted as a potential screening tool for an early IEI diagnosis, pivotal for appropriate clinical management and for the identification of new therapeutic targets.