CARMIL2 Deficiency Presenting as Very Early Onset Inflammatory Bowel Disease

Synchronous Epidermodysplasia Verruciformis and Intraepithelial Lesion of the Vulva Is Caused by Coinfection With Alpha-Human Papillomavirus and Beta-Human Papillomavirus Genotypes and Facilitated by Mutations in Cell-Mediated Immunity Genes

CONTEXT.—

There have been exceedingly few reports of epidermodysplasia verruciformis (EV) or EV-like lesions in the vulva. We describe the first observation of vulvar lesions displaying synchronous EV-like histology and conventional high-grade squamous intraepithelial lesion (HSIL), a finding hitherto unreported in medical literature.

OBJECTIVES.—

To describe this novel vulvar lesion with hybrid features of HSIL and EV, attempt to confirm the hypothesis of coinfection with α and β human papillomavirus (α-HPV and β-HPV) genotypes, and describe relevant underlying genetic mutations.

DESIGN.—

Cases were retrospectively selected from our institutional archive. Detailed review of clinical information, histologic examination, and whole genome sequencing (WGS) were performed.

RESULTS.—

Five samples from 4 different patients were included. Three of 4 patients had a history of either iatrogenic immune suppression or prior immune deficiency, and all 3 featured classic HSIL and EV changes within the same lesion. One patient had no history of immune disorders, presented with EV-like changes and multinucleated atypia of the vulva, and was the sole patient without conventional HSIL. By WGS, several uniquely mappable reads pointed toward infection with multiple HPV genotypes, including both α-HPVs and β-HPVs. Mutations in genes implicated in cell-mediated immunity, such as DOCK8, CARMIL2, MST1, and others, were also found.

CONCLUSIONS.—

We provide the first description of vulvar lesions harboring simultaneous HSIL and EV features in the English-language literature, a phenomenon explained by coinfection with α-HPV and β-HPV genotypes. The finding of EV-like changes in a vulvar specimen should prompt assessment of the patient's immune status.

Early Onset Inflammatory Bowel Disease Due to Immunodeficiency as a Result of ICOS Gene Homozygous Mutation

INTRODUCTION

Inflammatory bowel disease (IBD) is classified as very early-onset IBD (VEO-IBD) if it occurs before age six. VEO-IBD may progress with more severe and resistant inflammation findings in the gastrointestinal and non-gastrointestinal systems.

CASE REPORT

We describe the clinical presentation of a 4-year-old female presenting with recurring episodes of bloody diarrhea, vomiting, abdominal pain, fever, arthritis, erysipelas, and bilateral ankle pain. Monogenic primary immunodeficiency (PID) was suspected due to her age, different clinical findings and the presence of atypical gastroscopic findings and deep transmural ulcerations resembling Crohn's disease. The gene analysis showed a homozygous mutation in the inducible T cell co-stimulator (ICOS) deficiency genes.

DISCUSSION/CONCLUSION

This case presentation shares our clinical experience and demonstrates the link between IBD progression and ICOS deficiency.

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.

Understanding endoscopic and clinicopathological features of patients with very early onset inflammatory bowel disease: Results from a decade of study

BACKGROUND

Very early onset inflammatory bowel disease (VEOIBD) is associated with a unique disease course and distinct endoscopic features.

AIMS

This study aims to provide a comprehensive description of the endoscopic and histologic features observed in a large cohort of patients with VEOIBD from a tertiary medical center.

METHODS

A retrospective review of medical records from 2011 to 2021 was conducted to analyze clinical data, including disease phenotypes, endoscopic and histologic findings. Next generation sequencing was performed.

RESULTS

A total of 225 VEOIBD subjects were included in this study. Monogenic defects were identified in 161 patients. Monogenic IBD patients more commonly had CD-like disease. Colonic involvement was more prevalent among those with monogenic IBD (P<0.001). Pseudo-polyps were significantly more common in the monogenic IBD group (P<0.001), while ileal edema and ulcers were significantly more prevalent in non-monogenic IBD cases. IL10RA deficiency were characterized by colonic ulcers and pseudo-polyps without upper gastrointestinal tract lesions, while patients with TNFAIP3 mutations demonstrated both upper and lower gastrointestinal tract involvement. The non-monogenic IBD patients showed a higher incidence of chronic architectural changes of crypt, increased apoptosis and eosinophils infiltration.

CONCLUSIONS

Endoscopic and histologic analysis of children with VEOIBD plays a crucial role in facilitating accurate diagnosis. Various forms of monogenic IBD exhibit distinct endoscopic and pathologic changes.

Novel CARMIL2 (RLTPR) Mutation Presenting with Hyper-IgE and Eosinophilia: A Case Report

BACKGROUND

Inborn errors of immunity are a growing group of disorders with a wide spectrum of genotypic and phenotypic profiles. CARMIL2 (previously named RLTPR) deficiency is a recently described cause of immune dysregulation, mainly presenting with allergy, mucocutaneous infections, and inflammatory bowel disease. CARMIL2 deficiency is categorized under diseases of immune dysregulation with susceptibility to lymphoproliferative conditions.

CASE PRESENTATION

Here we describe a 29-years-old male from a consanguineous family, with food and sting allergy, allergic rhinitis, facial molluscum contagiosum (viral infection of the skin in the form of umbilicated papules), eosinophilia and highly elevated serum IgE level. Whole exome sequencing revealed numerous homozygous variants, including a CARMIL2 nonsense mutation, a gene regulating actin polymerization, and promoting cell protrusion formation.

CONCLUSION

The selective role of CARMIL2 in T cell activation and maturation through cytoskeletal organization is proposed to be the cause of immune dysregulation in individuals with CARMIL2 deficiency. CARMIL2 has an important role in immune pathways regulation, through cell maturation and differentiation, giving rise to a balance between Th1, Th2, and Th17 immune response. This case can improve the understanding of the different impacts of CARMIL2 mutations on immune pathways and further guide the diagnosis of patients with similar phenotypes.

Inborn errors of immunity underlying defective T-cell memory

PURPOSE OF REVIEW

T-cell memory is a complex process not well understood involving specific steps, pathways and different T-cell subpopulations. Inborn errors of immunity (IEIs) represent unique models to decipher some of these requirements in humans. More than 500 different IEIs have been reported to date, and recently a subgroup of monogenic disorders characterized by memory T-cell defects has emerged, providing novel insights into the pathways of T-cell memory generation and maintenance, although this new knowledge is mostly restricted to peripheral blood T-cell memory populations.

RECENT FINDINGS

This review draws up an inventory of the main and recent IEIs associated with T-cell memory defects and their mice models, with a particular focus on the nuclear factor kappa B (NF-κB) signalling pathway, including the scaffold protein capping protein regulator and myosin 1 linker 2 (CARMIL2) and the T-cell co-stimulatory molecules CD28 and OX-40. Besides NF-κB, IKZF1 (IKAROS), a key transcription factor of haematopoiesis and STAT3-dependent interleukin-6 signals involving the transcription factor ZNF341 also appear to be important for the generation of T cell memory. Somatic reversion mosaicism in memory T cells is documented for several gene defects supporting the critical role of these factors in the development of memory T cells with a potential clinical benefit.

SUMMARY

Systematic examination of T-cell memory subsets could be helpful in the diagnosis of IEIs.

Atopic manifestations of inborn errors of immunity

PURPOSE OF REVIEW

Allergy and atopic features are now well recognized manifestations of many inborn errors of immunity (IEI), and indeed may be the hallmark in some, such as DOCK8 deficiency. In this review, we describe the current IEI associated with atopy, using a comprehensive literature search and updates from the IUIS highlighting clinical clues for underlying IEI such as very early onset of atopic disease or treatment resistance to enable early and accurate genetic diagnosis.

RECENT FINDINGS

We focus on recently described genes, their categories of pathogenic mechanisms and the expanding range of potential therapies.

SUMMARY

We highlight in this review that patients with very early onset or treatment resistant atopic disorders should be investigated for an IEI, as targeted and effective therapies exist. Early and accurate genetic diagnosis is crucial in this cohort to reduce the burden of disease and mortality.

Gastrointestinal endoscopic findings of autoimmune and autoinflammatory diseases in pediatric rheumatology patients

OBJECTIVE

Rheumatic diseases in children are chronic and multisystemic diseases. In this study, it was aimed to evaluate gastrointestinal endoscopic findings in children diagnosed as autoimmune or autoinflammatory rheumatic diseases consulted with pediatric gastroenterology for gastrointestinal complaints.

METHODS

The patients followed up by the Pediatric Rheumatology Department and consulted to the Pediatric Gastroenterology Department due to gastrointestinal complaints were included in the study. File records of the patients were analyzed retrospectively.

RESULTS

A total of 28 patients were included in the study. Twelve of the patients had autoimmune disease (Juvenile idiopathic arthritis [JIA], systemic lupus erythematosus, Sjögren's syndrome, and scleroderma) and the other 16 had autoinflammatory disease (familial Mediterrnean fever, hyper Immunoglobulin D syndrome, undifferantiated systemic autoinflammatory disease, and systemic JIA). Four of the patients with familial Mediterrnean fever also diagnosed as JIA. The mean age of the patients was 11.7±3.5 years. The main gastrointestinal complaints of patients with both autoimmune and autoinflammatory diseases were abdominal pain and diarrhea. Inflammatory bowel disease was found in 33% of those with autoimmune disease and 56% of those with autoinflammatory disease in patients underwent endoscopic evaluation. M694V mutation was present in 62% of the patients with autoinflammatory disease presented with gastrointestinal complaints.

CONCLUSION

Both autoimmune and autoinflammatory rheumatic diseases can cause gastrointestinal complaints and should be referred to a pediatric gastroenterologist for early diagnosis.

Human CARMIL2 deficiency underlies a broader immunological and clinical phenotype than CD28 deficiency

Patients with inherited CARMIL2 or CD28 deficiency have defective T cell CD28 signaling, but their immunological and clinical phenotypes remain largely unknown. We show that only one of three CARMIL2 isoforms is produced and functional across leukocyte subsets. Tested mutant CARMIL2 alleles from 89 patients and 52 families impair canonical NF-κB but not AP-1 and NFAT activation in T cells stimulated via CD28. Like CD28-deficient patients, CARMIL2-deficient patients display recalcitrant warts and low blood counts of CD4+ and CD8+ memory T cells and CD4+ TREGs. Unlike CD28-deficient patients, they have low counts of NK cells and memory B cells, and their antibody responses are weak. CARMIL2 deficiency is fully penetrant by the age of 10 yr and is characterized by numerous infections, EBV+ smooth muscle tumors, and mucocutaneous inflammation, including inflammatory bowel disease. Patients with somatic reversions of a mutant allele in CD4+ T cells have milder phenotypes. Our study suggests that CARMIL2 governs immunological pathways beyond CD28.

CARMIL2 Immunodeficiency with Epstein Barr Virus Associated Smooth Muscle Tumor (EBV-SMT). Report of a Case with Comprehensive Review of Literature

Background: Primary immunodeficiency (PID) having defects related to lymphocyte cytotoxic pathway or T-cell dysfunction are well known for developing opportunistic infections and Epstein-Barr virus (EBV)-associated diseases. CARMIL2 deficiency is a recently described combined immunodeficiency (CID) disorder characterized by defective CD28-mediated T cell co-stimulation, altered cytoskeletal dynamics, susceptibility to various infections and Epstein Barr Virus smooth muscle tumor (EBV-SMT). Case report: We report a homozygous CARMIL2 pathogenic variant presenting with recurrent infections and EBV associated smooth muscle tumor (SMT) in a child. Conclusion: The present study reports that EBV SMT may occur in a child with CARMIL2 deficiency.

Evolution and long-term outcomes of combined immunodeficiency due to CARMIL2 deficiency

BACKGROUND

Biallelic loss-of-function mutations in CARMIL2 cause combined immunodeficiency associated with dermatitis, inflammatory bowel disease (IBD), and EBV-related smooth muscle tumors. Clinical and immunological characterizations of the disease with long-term follow-up and treatment options have not been previously reported in large cohorts. We sought to determine the clinical and immunological features of CARMIL2 deficiency and long-term efficacy of treatment in controlling different disease manifestations.

METHODS

The presenting phenotypes, long-term outcomes, and treatment responses were evaluated prospectively in 15 CARMIL2-deficient patients, including 13 novel cases. Lymphocyte subpopulations, protein expression, regulatory T (Treg), and circulating T follicular helper (cT_FH ) cells were analyzed. Three-dimensional (3D) migration assay was performed to determine T-cell shape.

RESULTS

Mean age at disease onset was 38 ± 23 months. Main clinical features were skin manifestations (n = 14, 93%), failure to thrive (n = 10, 67%), recurrent infections (n = 10, 67%), allergic symptoms (n = 8, 53%), chronic diarrhea (n = 4, 27%), and EBV-related leiomyoma (n = 2, 13%). Skin manifestations ranged from atopic and seborrheic dermatitis to psoriasiform rash. Patients had reduced proportions of memory CD4⁺ T cells, Treg, and cT_FH cells. Memory B and NK cells were also decreased. CARMIL2-deficient T cells exhibited reduced T-cell proliferation and cytokine production following CD28 co-stimulation and normal morphology when migrating in a high-density 3D collagen gel matrix. IBD was the most severe clinical manifestation, leading to growth retardation, requiring multiple interventional treatments. All patients were alive with a median follow-up of 10.8 years (range: 3-17 years).

CONCLUSION

This cohort provides clinical and immunological features and long-term follow-up of different manifestations of CARMIL2 deficiency.

Case report: Primary immunodeficiency due to a novel mutation in CARMIL2 and its response to combined immunomodulatory therapy

Capping protein regulator and myosin 1 linker 2 (CARMIL2) is necessary for invadopodia formation, cell polarity, lamellipodial assembly, membrane ruffling, acropinocytosis, and collective cell migration. CARMIL2 deficiency is a rare autosomal recessive disease characterized by dysfunction in naïve T-cell activation, proliferation, differentiation, and effector function and insufficient responses in T-cell memory. In this paper, we report a 9-year-old female patient with a novel pathogenic variant in CARMIL2 (c.2063C > G:p.Thr688Arg) who presented with various symptoms of primary immunodeficiencies including recurrent upper and lower respiratory infections, perioral and perineum papules, reddish impetiginized atopic dermatitis, oral ulcer, painful urination and vaginitis, otitis media, and failure to thrive. A missense mutation leading to insufficient CARMIL2 protein expression, reduced absolute T-cell and natural killer cell (NK cell) counts, and marked skewing to the naïve T-cell form was identified and indicated defective maturation of T cells and B cells. Following 1 year of multitargeted treatment with corticosteroids, hydroxychloroquine, mycophenolate mofetil, and thymosin, the patient presented with significant regression in rashes. CD4+ T-cell, CD8+ T-cell, and NK cell counts were significantly improved.

Novel Genetic Discoveries in Primary Immunodeficiency Disorders

The field of Immunology is one that has undergone great expansion in recent years. With the advent of new diagnostic modalities including a variety of genetic tests (discussed elsewhere in this journal), the ability to diagnose a patient with a primary immunodeficiency disorder (PIDD) has become a more streamlined process. With increased availability of genetic testing for those with suspected or known PIDD, there has been a significant increase in the number of genes associated with this group of disorders. This is of great importance as a misdiagnosis of these rare diseases can lead to a delay in what can be critical treatment options. At times, those options can include life-saving medications or procedures. Presentation of patients with PIDD can vary greatly based on the specific genetic defect and the part(s) of the immune system that is affected by the variation. PIDD disorders lead to varying levels of increased risk of infection ranging from a mild increase such as with selective IgA deficiency to a profound risk with severe combined immunodeficiency. These diseases can also cause a variety of other clinical findings including autoimmunity and gastrointestinal disease.

New Insights and Advances in Pathogenesis and Treatment of Very Early Onset Inflammatory Bowel Disease

Very early onset inflammatory bowel disease (VEO-IBD) is characterized by multifactorial chronic recurrent intestinal inflammation. Compared with elderly patients, those with VEO-IBD have a more serious condition, not responsive to conventional treatments, with a poor prognosis. Recent studies found that genetic and immunologic abnormalities are closely related to VEO-IBD. Intestinal immune homeostasis monogenic defects (IIHMDs) are changed through various mechanisms. Recent studies have also revealed that abnormalities in genes and immune molecular mechanisms are closely related to VEO-IBD. IIHMDs change through various mechanisms. Epigenetic factors can mediate the interaction between the environment and genome, and genetic factors and immune molecules may be involved in the pathogenesis of the environment and gut microbiota. These discoveries will provide new directions and ideas for the treatment of VEO-IBD.

Epstein-Barr Virus in Inborn Immunodeficiency-More Than Infection

Simple Summary

Epstein–Barr Virus (EBV) is a common virus that is readily controlled by a healthy immune system and rarely causes serious problems in infected people. However, patients with certain genetic defects of their immune system might have difficulties controlling EBV and often develop severe and life-threatening conditions, such as severe inflammation and malignancies. In this review, we provide a summary of inherited immune diseases that lead to a high susceptibility to EBV infection and discuss how this infection is associated with cancer development.

Abstract

Epstein–Barr Virus (EBV) is a ubiquitous virus affecting more than 90% of the world’s population. Upon infection, it establishes latency in B cells. It is a rather benign virus for immune-competent individuals, in whom infections usually go unnoticed. Nevertheless, EBV has been extensively associated with tumorigenesis. Patients suffering from certain inborn errors of immunity are at high risk of developing malignancies, while infection in the majority of immune-competent individuals does not seem to lead to immune dysregulation. Herein, we discuss how inborn mutations in TNFRSF9, CD27, CD70, CORO1A, CTPS1, ITK, MAGT1, RASGRP1, STK4, CARMIL2, SH2D1A, and XIAP affect the development, differentiation, and function of key factors involved in the immunity against EBV, leading to increased susceptibility to lymphoproliferative disease and lymphoma.

Novel CARMIL2 loss-of-function variants are associated with pediatric inflammatory bowel disease

CARMIL2 is required for CD28-mediated co-stimulation of NF-κB signaling in T cells and its deficiency has been associated with primary immunodeficiency and, recently, very early onset inflammatory bowel disease (IBD). Here we describe the identification of novel biallelic CARMIL2 variants in three patients presenting with pediatric-onset IBD and in one with autoimmune polyendocrine syndrome (APS). None manifested overt clinical signs of immunodeficiency before their diagnosis. The first patient presented with very early onset IBD. His brother was found homozygous for the same CARMIL2 null variant and diagnosed with APS. Two other IBD patients were found homozygous for a nonsense and a missense CARMIL2 variant, respectively, and they both experienced a complicated postoperative course marked by severe infections. Immunostaining of bowel biopsies showed reduced CARMIL2 expression in all the three patients with IBD. Western blot and immunofluorescence of transfected cells revealed an altered expression pattern of the missense variant. Our work expands the genotypic and phenotypic spectrum of CARMIL2 deficiency, which can present with either IBD or APS, aside from classic immunodeficiency manifestations. CARMIL2 should be included in the diagnostic work-up of patients with suspected monogenic IBD.

CARMIL2-related immunodeficiency manifesting with photosensitivity

We report a case of a newly recognized primary immunodeficiency due to biallelic mutations in CARMIL2 manifesting as an actinic prurigo-like photodermatitis, allergic diathesis and recurrent infections in a child. We present this case to highlight a rare phenotype seen in this T-cell immunodeficiency and provide an overview of other dermatologic manifestations among published reports of this condition.

A Novel Pathogenic Variant in CARMIL2 (RLTPR) Causing CARMIL2 Deficiency and EBV-Associated Smooth Muscle Tumors

CARMIL2 deficiency is a rare combined immunodeficiency (CID) characterized by defective CD28-mediated T cell co-stimulation, altered cytoskeletal dynamics, and susceptibility to Epstein Barr Virus smooth muscle tumors (EBV-SMTs). Case reports associated with EBV-SMTs are limited. We describe herein a novel homozygous CARMIL2 variant (c.1364_1393del) in two Saudi Arabian male siblings born to consanguineous parents who developed EBV-SMTs. CARMIL2 protein expression was significantly reduced in CD4+ T cells and CD8+ T cells. T cell proliferation on stimulation with soluble (s) anti-CD3 or (s) anti-CD3 plus anti-CD28 antibodies was close to absent in the proband, confirming altered CD28-mediated co-signaling. CD28 expression was substantially reduced in the proband's T cells, and was diminished to a lesser degree in the T cells of the younger sibling, who has a milder clinical phenotype. Defects in both T and B cell compartments were observed, including absent central memory CD8+ T cells, and decreased frequencies of total and class-switched memory B cells. FOXP3+ regulatory T cells (Treg) were also quantitatively decreased, and furthermore CD25 expression within the Treg subset was substantially reduced. These data confirm the pathogenicity of this novel loss-of-function (LOF) variant in CARMIL2 and expand the genotypic and phenotypic spectrum of CIDs associated with EBV-SMTs.

Exogenous interleukin-2 can rescue in-vitro T cell activation and proliferation in patients with a novel capping protein regulator and myosin 1 linker 2 mutation

Capping protein regulator and myosin 1 linker 2 (CARMIL2) deficiency is characterized by impaired T cell activation, which is attributed to defective CD28-mediated co-signaling. Herein, we aimed to analyze the effect of exogenous interleukin (IL)-2 on in-vitro T cell activation and proliferation in a family with CARMIL2 deficiency. This study included four children (one male and three females; aged 2·5-10 years at presentation). The patients presented with inflammatory bowel disease and recurrent viral infections. Genetic analysis revealed a novel homozygous 25-base pairs deletion in CARMIL2. Immunoblotting demonstrated the absence of CARMIL2 protein in all four patients and confirmed the diagnosis of CARMIL2 deficiency. T cells were activated in-vitro with the addition of IL-2 in different concentrations. CD25 and interferon (IFN)-γ levels were measured after 48 h and 5 days of activation. CD25 surface expression on activated CD8+ and CD4+ T cells was significantly diminished in all patients compared to healthy controls. Additionally, CD8+ T cells from all patients demonstrated significantly reduced IFN-γ production. When cells derived from CARMIL2-deficient patients were treated with IL-2, CD25 and IFN-γ production increased in a dose-dependent manner. T cell proliferation, as measured by Cell Trace Violet, was impaired in one patient and it was also rescued with IL-2. In conclusion, we found that IL-2 rescued T cell activation and proliferation in CARMIL2-deficient patients. Thus, IL-2 should be further studied as a potential therapeutic modality for these patients.

Human genetic dissection of papillomavirus-driven diseases: new insight into their pathogenesis

Human papillomaviruses (HPVs) infect mucosal or cutaneous stratified epithelia. There are 5 genera and more than 200 types of HPV, each with a specific tropism and virulence. HPV infections are typically asymptomatic or result in benign tumors, which may be disseminated or persistent in rare cases, but a few oncogenic HPVs can cause cancers. This review deals with the human genetic and immunological basis of interindividual clinical variability in the course of HPV infections of the skin and mucosae. Typical epidermodysplasia verruciformis (EV) is characterized by β-HPV-driven flat wart-like and pityriasis-like cutaneous lesions and non-melanoma skin cancers in patients with inborn errors of EVER1-EVER2-CIB1-dependent skin-intrinsic immunity. Atypical EV is associated with other infectious diseases in patients with inborn errors of T cells. Severe cutaneous or anogenital warts, including anogenital cancers, are also driven by certain α-, γ-, μ or ν-HPVs in patients with inborn errors of T lymphocytes and antigen-presenting cells. The genetic basis of HPV diseases at other mucosal sites, such as oral multifocal epithelial hyperplasia or juvenile recurrent respiratory papillomatosis (JRRP), remains poorly understood. The human genetic dissection of HPV-driven lesions will clarify the molecular and cellular basis of protective immunity to HPVs, and should lead to novel diagnostic, preventive, and curative approaches in patients.

Genetic susceptibility to EBV infection: insights from inborn errors of immunity

Epstein-Barr virus (EBV) is a ubiquitous human pathogen, infecting > 90% of the adult population. In the vast majority of healthy individuals, infection with EBV runs a relatively benign course. However, EBV is by no means a benign pathogen. Indeed, apart from being associated with at least seven different types of malignancies, EBV infection can cause severe and often fatal diseases-hemophagocytic lymphohistiocytosis, lymphoproliferative disease, B-cell lymphoma-in rare individuals with specific monogenic inborn errors of immunity. The discovery and detailed investigation of inborn errors of immunity characterized by heightened susceptibility to, or increased frequency of, EBV-induced disease have elegantly revealed cell types and signaling pathways that play critical and non-redundant roles in host-defense against EBV. These analyses have revealed not only mechanisms underlying EBV-induced disease in rare genetic conditions, but also identified molecules and pathways that could be targeted to treat severe EBV infection and pathological consequences in immunodeficient hosts, or even potentially enhance the efficacy of an EBV-specific vaccine.

Advanced Understanding of Monogenic Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a group of chronic disorders that cause relapsing inflammation in the gastrointestinal tract and comprise three major subgroups of Crohn's disease (CD), ulcerative colitis (UC), and IBD-unclassified (IBDU). Recent advances in genomic technologies have furthered our understanding of IBD pathogenesis. It includes differentiation rare monogenic disorders exhibiting IBD and IBD-like inflammation (monogenic IBD) from patients with the common polygenic form of IBD. Several novel genes responsible for monogenic IBD have been elucidated, and the number of reports has increased due to advancements in molecular functional analysis. Identification of these pathogenic genetic mutations has helped in elucidating the details of the immune response associated with gastrointestinal inflammation and in providing individualized treatments for patients with severe IBD that is often unresponsive to conventional therapy. The majority of monogenic IBD studies have focused on young children diagnosed <6 years of age (very early-onset IBD); however, a recent study revealed high prevalence of monogenic IBD in older children aged >6 years of age as well. Meanwhile, although patients with monogenic IBD generally show co-morbidities and/or extraintestinal manifestation at the time of diagnosis, cases of IBD developing as the initial symptom with unremarkable prodromal symptoms have been reported. It is crucial that the physicians properly match genetic analytical data with clinical diagnosis and/or differential diagnosis. In this review, we summarize the essential clues that may physicians make a correct diagnosis of monogenic disease, including classification, prevalence and clinical phenotype based on available literatures.