Human genetic and immunological determinants of Epstein-Barr virus-driven disease.

Conflicts of Interests: EYW receives consulting and speaker fees from Pharming Healthcare, Inc. regarding their work on the medication leniolisib approved for activated PI3 kinase delta syndrome (APDS). The remaining authors AHS and MK declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.The number of inborn errors of immunity (IEI) is growing rapidly (1). They can be challenging to diagnose given the expanding and variable clinical phenotypes (2,3). Specifically, there is an increasing recognition that immune dysregulation can be an initial or predominant manifestation of a substantive portion of IEIs (4,5). Immune dysregulation can also have a large impact on disease treatment, monitoring, and outcomes. Significant progress has been made in the elucidation of molecular and cellular mechanisms underlying the immune dysregulation of IEIs. Tremendous improvement has also been made in the management of IEIs with availability of therapies expanding to include biologics and small molecular inhibitors. Despite progress, more understanding is needed to tailor the use of immunomodulatory therapy in IEIs. This Research Topic "Immune Dysregulation in Inborn Errors of Immunity" highlights recent advances in the understanding of the prevalence, mechanisms, spectrum of manifestations, and management of immune dysregulation in IEIs. Gagne et al. provide a concise review of how Mendelian type I interferonopathies can masquerade as non-Mendelian autoimmune disorders like systemic lupus erythematosus (SLE) and dermatomyositis, which are also associated with increased type I interferon (IFN) expression. Similarly, Hetrick et al. described how autoinflammatory bone disorders characterized by sterile osteomyelitis can be seen with both monogenic forms including Majeed syndrome and deficiency of the interleukin-1 antagonist (DIRA) and the more common sporadic form chronic nonbacterial osteomyelitis (CNO) or chronic recurrent multifocal osteomyelitis (CRMO). Other autoimmune manifestations of IEIs include, but are not limited to, autoimmune cytopenia, endocrinopathies, inflammatory bowel disease, neutrophilic dermatoses, arthritis, and vasculitis as illustrated by the case of activated phosphoinositide 3-kinase delta (PI3Kd) syndrome (APDS) from Sood et al.The highly variable clinical manifestations of IEIs can contribute to diagnostic delays, which in turn, can lead to poorer outcomes. Autoimmunity and autoinflammation can negatively impact morbidity and mortality and are an independent prognostic factor for death among individuals with IEIs (5). Immune dysregulation may also contribute to the increased risk of malignancy observed in IEIs as with the APDS case presented by Sood et al.Improving awareness and early recognition of IEIs is also critical because making a diagnosis can impact treatment and surveillance. There may be disease-specific treatments available like leniolisib, an oral selective PI3Kd inhibitor, for APDS as discussed by Sood et al. Because type 1 IFN work through the janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway, Gagne et al. also consider the increasing use of JAK inhibition in autoinflammatory IFN-mediated monogenic diseases. The study by Berrueco et al. showed mycophenolate mofetil may be an effective and safe treatment for pediatric patients with autoimmune cytopenia and IEI, even cases of autoimmune cytopenia refractory to first-line therapies like corticosteroids and intravenous immunoglobulin (IVIG).These articles also nicely illustrate the need for a multidisciplinary approach to the immune dysregulatory manifestations in IEIs as there are contributions from Rheumatology (inteferonopathies and pediatric autoinflammatory bone disorders), Hematology (autoimmune cytopenias), and Allergy/Immunology (APDS). The conditions covered in this topic represent only a fraction of disordered immune conditions in IEIs and should be considered in more detail in the future.The recognition of immune dysregulation in IEIs continues to increase as the number of patients impacted expands. There is a clear need for ongoing investigation into the epidemiology and pathophysiology for clinical manifestations and the risk factors for developing immune dysregulation as well as a collaborative multidisciplinary approach to improve diagnosis and management of this population. Our hope is that this topic has piqued the interest of researchers and clinicians in this area to provide better understanding, care, and outcomes to these patients.Lastly, we would like to thank the reviewers for their time and valuable assessments. This important collection of articles would not be possible without their contributions.

Immune dysregulation is being increasingly recognized as a leading sign of a wide spectrum of inborn errors of immunity (IEIs). Therefore, patients with IEIs are frequently managed in non-immunological settings, including hematology and oncology units, during the diagnostic process or follow-up. The most relevant hematological signs associated with IEIs comprise autoimmune cytopenia (AIC), lymphoproliferative diseases (LPD), malignancies, hemophagocytic lymphohystiocitosis (HLH), bone marrow failure (BMF), myelodysplastic syndromes (MDS), and peripheral or tissue eosinophilia. The prognosis of patients with IEIs can significantly improve when a molecular diagnosis is established, as it can allow the use of targeted treatments, guide appropriate follow-up strategies and, in some cases, support the rationale for hematopoietic stem cell transplantation or gene therapy. Therefore, there is an urgent need to recognize the warning signs suggestive for an underlying IEI among patients presenting with common hematological features and to ensure an appropriate diagnostic approach. As a general rule, clinicians should always provide a clinical alert in the presence of two or more IEI-associated hematological signs, as well as a positive familial history for IEI or hematologic immune dysregulation, a personal history of severe infections, and other signs of immune dysregulation. Concerning AIC, an increased likelihood of IEI is characteristic of patients with treatment refractoriness, autoimmune hemolytic anemia, or multilineage cytopenia. In the case of LPD, the main elements of suspicion are represented by the chronic or recurrent disease course, the persistence of Epstein–Barr Virus (EBV) infection, and the development of lymphoproliferation in atypical localizations. Among patients with malignancy, clinicians should investigate for IEI those with rare neoplasia, virus-associated tumors, and an association with syndromic features, while patients with HLH should always receive an immunological assessment when a clear rheumatologic trigger, underlying malignancy, or well-recognized cause is not evident. The case of MDS and BMF is complex, as new monogenic entities are continuously being described. However, it is pivotal to consider the presence of monocytopenia, warts, vasculitis, and neurological disease, as well as specific cytogenetic abnormalities, such as chromosome 7 monosomy, as warning sings for IEIs. Finally, the main red flags for IEIs in patients with eosinophilia are skeletal/facial abnormalities, recurrent abscesses, refractory eczema, organomegaly, or thrombocytopenia.

Background:Systemic lupus erythematosus (SLE) is a systemic autoimmune disease caused by immune dysregulation and characterized by the production of a large number of autoantibodies leading to multiple organ involvement. Despite...

BackgroundPatients with inborn errors of immunity (IEI) have increased risk of developing cancers secondary to impaired anti-tumor immunity. Treatment of patients with IEI and cancer is challenging as chemotherapy can exacerbate infectious susceptibility. However, the literature on optimal cancer treatment in the setting of IEI is sparse.ObjectivesWe present a patient with specific antibody deficiency with normal immunoglobins (SADNI), immune dysregulation (ID), and stage III ovarian carcinoma as an example of the need to modify conventional treatment in the context of malignancy, IEI, and ongoing infections.MethodsThis is a retrospective chart review of the patient’s clinical manifestations, laboratory evaluation and treatment course.ResultsOur patient is a female with SADNI and ID diagnosed with stage III ovarian carcinoma at 60 years of age. Her ID accounted for antinuclear antibody positive (ANA+) mixed connective tissue diseases, polyarthralgia, autoimmune neutropenia, asthma, autoimmune thyroiditis, and Celiac disease. Due to the lack of precedent in the literature, her treatment was modified with continuous input from infectious disease, allergy/immunology and oncology specialist using a multidisciplinary approach.The patient completed debulking surgery and 6 cycles of chemotherapy. The dosing for immunoglobulin replacement therapy was increased for prophylaxis. Chemotherapy doses were lowered for all cycles preemptively for IEI. The therapy included carboplatin, paclitaxel, bevacizumab, and pegfilgrastim. The patient completed six-months of maintenance medication involving bevacizumab.Her treatment course was complicated by Mycobacterium avium-complex (MAC) infection, elevated bilirubin and liver enzymes attributed to excessive immunoglobulin replacement therapy, and urinary tract infection (UTI) and incontinence.Cancer genetic analysis revealed no targetable markers and primary immunodeficiency gene panel of 407 genes by Invitae was unrevealing. Lab tests revealed no evidence of Epstein-Barr Virus (EBV) infection. Post-chemotherapy imaging revealed no evidence of cancer for 1 year and 4 months, but the disease relapsed subsequently. The patient’s lung scarring requires vigilance.ConclusionsOur patient with ovarian cancer and IEI required modified treatment and prevention of complications. In cases of IEI, optimal chemotherapy should be titrated to minimize immunosuppression yet treat cancer aggressively while decreasing the risk of infection with prophylactic antibiotics and prolonged post-treatment surveillance, including pulmonary evaluation.

Introduction. Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by various manifestations and clinical course, many aspects of the etiology and pathogenesis of which remain unclear. Recently, the interest of researchers in studying the role of cytomegalovirus (CMV) and Epstein - Barr virus (EBV) has been growing in the occurrence and course of a number of human diseases due to their ability to affect almost all organs and systems of the body, causing the formation of latent, active or chronic infection, which can often cause temporary disability, disability or even death, however, for the patients with SLE, despite the possibility of approaching the difficult problem of diagnosis and treatment of this disease, this issue is given insufficient attention, as evidenced by isolated studies.The aim of the study. Detect cytomegalovirus and Epstein - Barr infection in patients with systemic lupus erythematosus and its dependence on gender and age of patients. Materials and methods of research. The study involved 120 patients (15 men (12.50%) and 105 women (87.50%) aged 18 to 69 years with SLE, who were in the rheumatology department of the Communal Non-Commercial Enterprise of the Lviv Regional Council "Lviv Regional Clinical Hospital" in 2014-2019. To diagnose CMV and EBV infection by enzyme-linked immunosorbent assay, antibodies of IgM and IgG to viruses were detected in blood serum, and viruses were detected by polymerase chain reaction. According to the results of virus detection, formed groups of the patients, namely: patients with active CMV infection, active EBV, active CMV and EBV, without active CMV and EBV. All patients with SLE included in the study were subsequently stratified by age according to the classification of the World Health Organization (2015), according to which the following age limits were determined: young age, middle-aged, elderly, senile. Statistical analysis was performed on a personal computer in MS Excel and Statistica 6.0 using descriptive statistics. The frequency of cases of active CMV and EBV infection was calculated mathematically by the binomial coefficient of I. Newton. Research results and their discussion. We found in the vast majority of patients with SLE (117 patients, 97.50%) increase in the titer of specific antibodies to CMV. Only in 3 patients (2.50%) the titer of antibodies to this virus was within normal limits. Analyzing the frequency of EBV infection in patients with SLE, we recorded an increase in the titer of specific antibodies to the virus in 119 patients (99.17%). Among the examined patients with SLE in all (100.00%) found an increase in the titer of antibodies to CMV and / or EBV, of which 97.50% - infected with CMV and 97.17% - infected with EBV. The active phase of CMV and / or EBV infection was detected in 54.17%, of which 23.33% - active CMV infection, 17.50% - active EBV infection and 12.50% - a combination of active CMV and EBV infection simultaneously, which indicates a high frequency of CMV and EBV infection in patients with SLE and reflects the urgency of the problem of diagnosing herpesvirus infection in them. We found that activeCMV, EBV infections and their combinations are present only in women (64 patients, which is 60.96% of the total number of women with SLE), of which 28 patients (26.67%) there was only active CMV infection, in 21 patients (20.00%) - only active EBV infection and in 15 patients (14.29%) – combination of active CMV and EBV infection. 41 women (39.05%) and all (100.00%) men were not found to have active CMV and EBV infection, which indicates that men at the time of the survey were significantly more likely to have this infection in the integration phase. The most frequently active EBV infection was detected in patients with SLE of young age (17 cases, 24.64%), and in middle-aged patients 3 cases (6.52%) were recorded, which indicates a significant (p <0.05) difference in the frequency of cases of active EBV infection in patients of both groups. Only 1 case (20.00%) of active EBV infection was detected in elderly patients. Conclusions. All patients with systemic lupus erythematosus are infected - 97.50% with cytomegalovirus and 97.17% with Epstein-Barr virus infection, that was confirmed by the increased titer of antibodies to them. Among the mentioned patients 53.33% of them had the active phase of infection (23.33% - cytomegalovirus infection in the replication phase, 17.50% - the Epstein- Barr virus infection in the replication phase and 12.50% - their combination). The prevalence of active viral infection in patients with systemic lupus erythematosus depends on gender (active cytomegalovirus, active Epstein-Barr virus infection and their combination are significantly more common in women) and age - they are probably more common in young patients.

Background Inborn Errors of Immunity (IEI), previously termed primary immunodeficiencies, include a wide range of disorders characterized by immune dysregulation, autoimmunity, and susceptibility to infections. Objective This study aims to identify non-infectious warning signs of IEI in children of autoimmune disorders presenting with atypical noninfectious symptoms, facilitating early diagnosis and intervention. Methods This cross-sectional study included 100 children below the age of 18 with different immunological disorders and suspected of having IEI. Twenty-two cases were confirmed using clinical and laboratory evaluations. Data collected included demographic details, clinical examinations, and laboratory investigations such as immunoglobulin levels (IgA, IgM, IgG, IgE), CD markers (CD3, CD4, CD8, CD19, CD56), and specific protein analyses (e.g., DOCK8, LRBA, WAS), using flow cytometry and targeted intracellular protein analysis. Correlation between clinical features and confirmed IEI was assessed using Pearson’s correlation coefficient. Results Among the studied cases, immune thrombocytopenic purpura (ITP) was the most common diagnosis (19%), followed by systemic lupus erythematosus (SLE, 16%), type 1 diabetes mellitus (15%), inflammatory bowel disease (IBD, 13%), and autoimmune hemolytic anemia (8%). From the 100 enrolled patients, 22 (22%) were diagnosed with IEI. The mean age of participants was 9.04 ± 4.4 years, with a male predominance (72.7%) among confirmed IEI cases. Autoimmune lymphoproliferative syndrome (ALPS) was the most frequent IEI disorder (18.2%), followed by DOCK8 deficiency, adenosine deaminase 2 deficiency, and common variable immunodeficiency (each 13.6%). Common presenting complaints included diarrhea (31.8%), recurrent anemia (22.7%), and recurrent fever (18.2%). Hepatosplenomegaly (22.7%) and lymphadenopathy were the most frequent clinical findings. Hepatosplenomegaly (22.7%) was strongly associated with confirmed IEI (r = 0.67, p < 0.001). Other significant correlations included failure to thrive (r = 0.61, p = 0.001), autoimmune cytopenias (r = 0.56, p = 0.005), lymphadenopathy (r = 0.52, p = 0.01), eczema (r = 0.48, p = 0.02), and recurrent fever (r = 0.44, p = 0.03). A wide variation in immunoglobulin levels was observed, including low CD19 and CD56 levels, and normal complement profiles. Elevated IgE levels were observed, and autoimmune hemolysis was evident in confirmed IEI patients. Conclusion This study highlights the importance of recognizing non-infectious manifestations, such as autoimmune cytopenia, atopy, and lymphoproliferation, as potential indicators of IEI, even with the absence of recurrent or severe infections. Early identification of these signs can reduce diagnostic delays and improve outcomes in pediatric patients.

Immune dysregulation, including autoimmunity, autoinflammation, allergy, and malignancy predisposition, adds significant disease burden in primary immune disorders (PID) and inborn errors of immunity (IEIs). We evaluated whether the 5-graded immune deficiency and dysregulation activity (IDDA2.1) score, encompassing 21 organ involvement and disease burden parameters, supports diagnosis across a wide spectrum of IEIs. From April 2022 to November 2024, collaborators from 84 centers collected 1,043 IDDA score datasets from 825 patients across 89 IEIs (17 disorders with ≥10 patients each; range, 1-196 per IEI), including 177 scores from 141 treated patients. Supervised machine learning models (k-nearest neighbors, support vector machine, logistic regression, random forest) classified patients into disease groups and ranked corresponding predictive features, while unsupervised uniform manifold approximation and projection (UMAP) visualized disease-specific clustering. Feature analysis reflected clinicians' recognition of IEI patterns and confirmed internal IDDA score consistency. Phenotype profiles in treated patients remained informative, inversely reflecting anticipated treatment-dependent phenotype amelioration. UMAP effectively distinguished IEIs by IDDA2.1 profiles. Genetic disorder prediction achieved 73% overall accuracy, 70% for the correct monogenic IEI, and 93% within the top 3 predictions; classification reached 43% for IEI-International Union of Immunological Society categories and 59% for 12 "cardinal" IEIs (25 genes). Random forest feature importance analysis can inform targeted clinical screening for key disease manifestations. The top 3 prediction approach demonstrates diagnostic potential, but improved accuracy will require larger, globally shared datasets. Small sample sizes for rare diseases highlight the necessity of broader collaboration to enhance AI-assisted clinical decision-making in the future.

Background Inborn errors of immunity (IEI) are congenital disorders of the immune system. Due to impaired immune system, they are at a higher risk to develop a more severe COVID-19 course compared to general population. Objectives Herein, we aimed to systematically review various aspects of IEI patients infected with SARS-CoV-2. Moreover, we performed a meta-analysis to determine the frequency of COVID-19 in patients with different IEI. Methods Embase, Web of Science, PubMed, and Scopus were searched introducing terms related to IEI and COVID-19. Results 3646 IEI cases with a history of COVID-19 infection were enrolled. The majority of patients had critical infections (1013 cases, 27.8%). The highest frequency of critical and severe cases was observed in phenocopies of IEI (95.2%), defects in intrinsic and innate immunity (69.4%) and immune dysregulation (23.9%). 446 cases (12.2%) succumbed to the disease and the highest mortality was observed in IEI phenocopies (34.6%). COVID-19 frequency in immunodeficient patients was 11.9% (95% CI: 8.3 to 15.5%) with innate immunodeficiency having the highest COVID-19 frequency [34.1% (12.1 to 56.0%)]. COVID-19 case fatality rate among IEI patients was estimated as 5.4% (95% CI: 3.5–8.3%, n = 8 studies, I2 = 17.5%). Conclusion IEI with underlying defects in specific branches of the immune system responding to RNA virus infection experience a higher frequency and mortality of COVID-19 infection. Increasing awareness about these entities and underlying genetic defects, adherence to prophylactic strategies and allocating more clinical attention to these patients could lead to a decrease in COVID-19 frequency and mortality in these patients.

More than 500 primary immunodeficiencies (PIDs) or inborn errors of immunity (IEIs) have been reported. In general, IEIs are caused by monogenic germinal variants resulting in immunodeficiency and immune dysregulation symptoms. These "in natura" experiments have highlighted selective factors and pathways required for the immune control of a given pathogen, including Epstein-Barr virus (EBV). Several IEIs predominantly predispose to develop severe EBV infections and associated diseases including infectious mononucleosis (IM), hemophagocytic lymphohistiocytosis (HLH) and nonmalignant or malignant B cell lymphoproliferative disorders (B-LPD). Identification of these IEIs revealed critical components/molecules of the immune response to EBV. Notably, these elements differ depending on the type of the EBV viral disease. On one hand, defects in factors involved in the cytotoxic responses of lymphocytes preferentially underlie HLH, whereas, on the other hand, factors implicated in the expansion of EBV-specific T cells are mostly responsible for B-LPD when impaired. IEIs also inform on mechanisms underlying rare EBV viral diseases such as EBV+ smooth muscle tumors(EBV+SMT) and the "atypical" T/NK cell lymphoproliferative disorders (NK/T-LPD) including chronic active EBV infections (CAEBV). Finally, IEIs not predisposing to EBV provide information on immune components not necessary or redundant for EBV immunity. All these aspects are discussed in this chapter.

Quantifying the phenotypic features of rare diseases such as inborn errors of immunity (IEI) helps clinicians make diagnoses, classify disorders, and objectify the disease severity at its first presentation as well as during therapy and follow-up. Furthermore, it may allow cross-sectional and cohort comparisons and support treatment decisions such as an evaluation for transplantation. On the basis of a literature review, we provide a descriptive comparison of ten selected scores and measures frequently used in IEI and divide these into three categories: (1) diagnostic tools (for Hyper-IgE syndrome, hemophagocytic lymphohistiocytosis, and Wiskott-Aldrich syndrome), (2) morbidity and disease activity measures (for common variable immune deficiency [CVID], profound combined immune deficiency, CTLA-4 haploinsufficiency, immune deficiency and dysregulation activity [IDDA], IPEX organ impairment, and the autoinflammatory disease activity index), and (3) treatment stratification scores (shown for hypogammaglobulinemia). The depth of preclinical and statistical validations varies among the presented tools, and disease-inherent and user-dependent factors complicate their broader application. To support a comparable, standardized evaluation for prospective monitoring of diseases with immune dysregulation, we propose the IDDA2.1 score (comprising 22 parameters on a 2–5-step scale) as a simple yet comprehensive and powerful tool. Originally developed for use in a retrospective study in LRBA deficiency, this new version may be applied to all IEI with immune dysregulation. Reviewing published aggregate cohort data from hundreds of patients, the IDDA kaleidoscope function is presented for 18 exemplary IEI as an instructive phenotype–pattern visualization tool, and an unsupervised, hierarchically clustered heatmap mathematically confirms similarities and differences in their phenotype expression profiles.

Remembering Other Causes of Alveolar Siderophages: Macrophage Activation Syndrome

Rare but not forgotten, a case of evan's syndrome.

Chronic infections significantly impact the immune system, contributing to dysregulation and the development of autoimmune diseases. Persistent pathogens, such as viruses and bacteria, can evade immune clearance, leading to a sustained inflammatory response that disrupts the delicate balance of immune tolerance and activation. This review explores the mechanisms through which chronic infections influence immune system dynamics, focusing on the role of cytokines, immune cell modulation, and the alteration of immune signaling pathways. Infections like hepatitis C, Epstein-Barr virus, and others have been linked to autoimmune conditions such as systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis. The persistent presence of these pathogens may lead to molecular mimicry, epitope spreading, and the activation of autoreactive T and B cells, driving the pathogenesis of autoimmunity. Additionally, we discuss the implications of chronic infections on therapeutic strategies for autoimmune diseases, emphasizing the need for a comprehensive understanding of the interplay between infections and autoimmune dysregulation. By elucidating the complex relationships between chronic infections and the immune system, this review aims to highlight potential avenues for developing targeted interventions and improving patient outcomes in autoimmune disorders. Keywords: Chronic Infections, Immune Dysregulation, Autoimmune Diseases, Cytokines, Pathogenesis

In addition to susceptibility to infections, conventional primary immunodeficiency disorders (PIDs) and inborn errors of immunity (IEI) can cause immune dysregulation, manifesting as lymphoproliferative and/or autoimmune disease. Autoimmunity can be the prominent phenotype of PIDs and commonly includes cytopenias and rheumatological diseases, such as arthritis, systemic lupus erythematosus (SLE), and Sjogren’s syndrome (SjS). Recent advances in understanding the genetic basis of systemic autoimmune diseases and PIDs suggest an at least partially shared genetic background and therefore common pathogenic mechanisms. Here, we explore the interconnected pathogenic pathways of autoimmunity and primary immunodeficiency, highlighting the mechanisms breaking the different layers of immune tolerance to self-antigens in selected IEI.

Introduction X-linked lymphoproliferative disease (XLP) is a rare inborn error of immunity (IEI) characterized by increased susceptibility to Epstein–Barr Virus (EBV) and other features of immune dysregulation. We present a case of XLP1, diagnosed in a 37-year-old male with EBV viremia treated with nivolumab. Case The proband was diagnosed with common variable immunodeficiency (CVID) and started on IVIG at age 8. Infections were recurrent pneumonias and an episode of septic hip arthritis. He remained infection free over the next 3 decades until presenting with Evans syndrome at age 37, which was initially treated with prednisone. Shortly after, his course was complicated with hepatic and brain abscesses and liver decompensation. Thus, he was referred to our service for workup. Genetic testing revealed the diagnosis of XLP1 (SH2D1A c.138-2A>G). He was found to have EBV viremia, and a liver biopsy suggested EBV hepatitis. He was not a liver transplant candidate due to concern of sepsis given his immunosuppression and IEI. Hematopoietic stem cell transplant (HSCT) was not offered due to high risk of mortality. Despite treatment with rituximab, his repeat EBV titers continued to rise. Virus-specific T cell therapy was pursued; however, the patient was clinically too unstable to be transferred for treatment to the United States from Canada. He was given one nivolumab dose, significantly reducing his viremia. He ultimately succumbed to sepsis and respiratory failure. EBV is the leading cause of mortality in patients with XLP who forego HSCT. Rituximab has been well-documented in the treatment of EBV. We present a patient with an EBV susceptibility syndrome and progressive viremia, who responded well to one dose of nivolumab which significantly reduced his EBV viral load. Despite limited literature, nivolumab may play a significant role in the treatment of certain EBV-associated conditions, particularly in patients with IEIs. In conclusion, nivolumab should be considered for any patient with an overwhelming EBV infection. Severe EBV-induced disease is an unexpected finding in an individual with CVID and warrants genetic testing to exclude other primary immunodeficiencies. Treatment options for EBV susceptibility syndromes need further exploration and accessibility.