COVID-19 Vaccination in Patients with Inborn Errors of Immunity Reduces Hospitalization and Critical Care Needs Related to COVID-19: a USIDNET Report.

BACKGROUND: The CDC and ACIP recommend COVID-19 vaccination for patients with inborn errors of immunity (IEI). Not much is known about vaccine safety in IEI, and whether vaccination attenuates infection severity in IEI. OBJECTIVE: To estimate COVID-19 vaccination safety and examine effect on outcomes in patients with IEI. METHODS: We built a secure registry database in conjunction with the US Immunodeficiency Network to examine vaccination frequency and indicators of safety and effectiveness in IEI patients. The registry opened on January 1, 2022, and closed on August 19, 2022. RESULTS: Physicians entered data on 1245 patients from 24 countries. The most common diagnoses were antibody deficiencies (63.7%). At least one COVID-19 vaccine was administered to 806 patients (64.7%), and 216 patients received vaccination prior to the development of COVID-19. The most common vaccines administered were mRNA-based (84.0%). Seventeen patients were reported to seek outpatient clinic or emergency room care for a vaccine-related complication, and one patient was hospitalized for symptomatic anemia. Eight hundred twenty-three patients (66.1%) experienced COVID-19 infection. Of these, 156 patients required hospitalization (19.0%), 47 required ICU care (5.7%), and 28 died (3.4%). Rates of hospitalization (9.3% versus 24.4%, p < 0.001), ICU admission (2.8% versus 7.6%, p = 0.013), and death (2.3% versus 4.3%, p = 0.202) in patients who had COVID-19 were lower in patients who received vaccination prior to infection. In adjusted logistic regression analysis, not having at least one COVID-19 vaccine significantly increased the odds of hospitalization and ICU admission. CONCLUSION: Vaccination for COVID-19 in the IEI population appears safe and attenuates COVID-19 severity.

Gut microbiome is associated with asthma and race in children with food allergy.

BACKGROUND: The composition of the gut microbiome has been associated with development of atopic conditions such as food allergy (FA) and asthma. African American or Black children with FA have higher rate of asthma compared to their White counterparts. OBJECTIVE: We sought to investigate whether the diversity and relative abundance (RA) of gut microbiota is different between children with FA from different racial backgrounds living in the same cities. Furthermore, we aimed to understand whether the difference in the gut microbiota is associated with asthma in children with FA. METHODS: We analyzed and compared the stool microbiome of a cohort of Black and White children with FA by shotgun genomic sequencing. RESULTS: A total of 152 children with IgE-mediated FA enrolled onto FORWARD (Food Allergy Outcomes Related to White and African American Racial Differences); 30 Black and 122 White children were included. The RA of several bacteria was associated with race and asthma. Most notably the RA of Bacteroides thetaiotaomicron, Chlamydia thrachomatis, Parabacteroides goldsteinii, and Bacteroides eggerthii were significantly higher, while the RA of Bifidobacterium sp CAG:754, Parabacterium johnsonii, Bacteroides intestinalis, and Bifidobacterium breve were significantly lower in stool samples of Black children compared to White children. Asthma was associated with lower RA of B breve, Bifidobacterium catenulatum, Prevotella copri, Veilloella sp CAG:933, and Bacteroides plebius, and higher RA of 3 Bacteroides species. CONCLUSIONS: The observed variations in the gut microbiota of Black and White children such as differences in the Bacteroides and Bifidobacterium species along with their association to history of asthma in our cohort is indicative of their potential role in the higher rate of asthma observed among Black children with FA.

Breakthroughs in understanding and treating eosinophilic gastrointestinal diseases presented at the CEGIR/TIGERs Symposium at the 2022 American Academy of Allergy, Asthma & Immunology Meeting.

The Consortium of Eosinophilic Gastrointestinal Diseases and The International Gastrointestinal Eosinophil Researchers organized a day-long symposium at the 2022 Annual Meeting of the American Academy of Allergy, Asthma & Immunology. The symposium featured a review of recent discoveries in the basic biology and pathogenesis of eosinophilic gastrointestinal diseases (EGIDs) in addition to advances in our understanding of the clinical features of EGIDs. Diagnostic and management approaches were reviewed and debated, and clinical trials of emerging therapies were highlighted. Herein, we briefly summarize the breakthrough discoveries in EGIDs.

Anaphylaxis knowledge gaps and future research priorities: A consensus report.

BACKGROUND: Despite a better understanding of the epidemiology, pathogenesis, and management of patients with anaphylaxis, there remain knowledge gaps. Enumerating and prioritizing these gaps would allow limited scientific resources to be directed more effectively. OBJECTIVE: We sought to systematically describe and appraise anaphylaxis knowledge gaps and future research priorities based on their potential impact and feasibility. METHODS: We convened a 25-member multidisciplinary panel of anaphylaxis experts. Panelists formulated knowledge gaps/research priority statements in an anonymous electronic survey. Four anaphylaxis themed writing groups were formed to refine statements: (1) Population Science, (2) Basic and Translational Sciences, (3) Emergency Department Care/Acute Management, and (4) Long-Term Management Strategies and Prevention. Revised statements were incorporated into an anonymous electronic survey, and panelists were asked to rate the impact and feasibility of addressing statements on a continuous 0 to 100 scale. RESULTS: The panel generated 98 statements across the 4 anaphylaxis themes: Population Science (29), Basic and Translational Sciences (27), Emergency Department Care/Acute Management (24), and Long-Term Management Strategies and Prevention (18). Median scores for impact and feasibility ranged from 50.0 to 95.0 and from 40.0 to 90.0, respectively. Key statements based on median rating for impact/feasibility included the need to refine anaphylaxis diagnostic criteria, identify reliable diagnostic, predictive, and prognostic anaphylaxis bioassays, develop clinical prediction models to standardize postanaphylaxis observation periods and hospitalization criteria, and determine immunotherapy best practices. CONCLUSIONS: We identified and systematically appraised anaphylaxis knowledge gaps and future research priorities. This study reinforces the need to harmonize scientific pursuits to optimize the outcomes of patients with and at risk of anaphylaxis.

Severity grading system for acute allergic reactions: A multidisciplinary Delphi study.

BACKGROUND: There is no widely adopted severity grading system for acute allergic reactions, including anaphylactic and nonanaphylactic reactions, thus limiting the ability to optimize and standardize management practices and advance research. OBJECTIVE: The aim of this study was to develop a severity grading system for acute allergic reactions for use in clinical care and research. METHODS: From May to September 2020, we convened a 21-member multidisciplinary panel of allergy and emergency care experts; 9 members formed a writing group to critically appraise and assess the strengths and limitations of prior severity grading systems and develop the structure and content for an optimal severity grading system. The entire study panel then revised the grading system and sought consensus by utilizing Delphi methodology. RESULTS: The writing group recommended that an optimal grading system encompass the severity of acute allergic reactions on a continuum from mild allergic reactions to anaphylactic shock. Additionally, the severity grading system must be able to discriminate between clinically important differences in reaction severity to be relevant in research while also being intuitive and straightforward to apply in clinical care. Consensus was reached for all elements of the proposed severity grading system. CONCLUSION: We developed a consensus severity grading system for acute allergic reactions, including anaphylactic and nonanaphylactic reactions. Successful international validation, refinement, dissemination, and application of the grading system will improve communication among providers and patients about the severity of allergic reactions and will help advance future research.

AR101 Oral Immunotherapy for Peanut Allergy.

BACKGROUND: Peanut allergy, for which there are no approved treatment options, affects patients who are at risk for unpredictable and occasionally life-threatening allergic reactions. METHODS: In a phase 3 trial, we screened participants 4 to 55 years of age with peanut allergy for allergic dose-limiting symptoms at a challenge dose of 100 mg or less of peanut protein (approximately one third of a peanut kernel) in a double-blind, placebo-controlled food challenge. Participants with an allergic response were randomly assigned, in a 3:1 ratio, to receive AR101 (a peanut-derived investigational biologic oral immunotherapy drug) or placebo in an escalating-dose program. Participants who completed the regimen (i.e., received 300 mg per day of the maintenance regimen for approximately 24 weeks) underwent a double-blind, placebo-controlled food challenge at trial exit. The primary efficacy end point was the proportion of participants 4 to 17 years of age who could ingest a challenge dose of 600 mg or more, without dose-limiting symptoms. RESULTS: Of the 551 participants who received AR101 or placebo, 496 were 4 to 17 years of age; of these, 250 of 372 participants (67.2%) who received active treatment, as compared with 5 of 124 participants (4.0%) who received placebo, were able to ingest a dose of 600 mg or more of peanut protein, without dose-limiting symptoms, at the exit food challenge (difference, 63.2 percentage points; 95% confidence interval, 53.0 to 73.3; P<0.001). During the exit food challenge, the maximum severity of symptoms was moderate in 25% of the participants in the active-drug group and 59% of those in the placebo group and severe in 5% and 11%, respectively. Adverse events during the intervention period affected more than 95% of the participants 4 to 17 years of age. A total of 34.7% of the participants in the active-drug group had mild events, as compared with 50.0% of those in the placebo group; 59.7% and 44.4% of the participants, respectively, had events that were graded as moderate, and 4.3% and 0.8%, respectively, had events that were graded as severe. Efficacy was not shown in the participants 18 years of age or older. CONCLUSIONS: In this phase 3 trial of oral immunotherapy in children and adolescents who were highly allergic to peanut, treatment with AR101 resulted in higher doses of peanut protein that could be ingested without dose-limiting symptoms and in lower symptom severity during peanut exposure at the exit food challenge than placebo. (Funded by Aimmune Therapeutics; PALISADE ClinicalTrials.gov number, NCT02635776 .).

Food allergy-related bullying and associated peer dynamics among Black and White children in the FORWARD study.

BACKGROUND: The experiences of Black children with food allergy (FA) are not well characterized, particularly with respect to bullying victimization and other psychosocial outcomes. OBJECTIVE: To evaluate bullying experiences of Black and White children with FA, including associations with peer relationships, anxiety, and school policies. METHODS: Surveys were administered to parents of 252 children with physician-diagnosed FA enrolled in the multisite FORWARD cohort. The surveys assessed demographics, atopic disease, bullying victimization, and school FA management practices and policies. Descriptive statistics of bullying by race were compared by χ2 tests. Multiple logistic regression analyses adjusting for race, age, parental education, household income, child sex, and multi-FA compared adjusted probabilities of bullying victimization by school policies. RESULTS: Nearly 20% of school-aged children were bullied for FA with no substantial racial differences overall, though for children ages 11 years and up, White children reported higher rates of bullying. However, Black children experienced non-FA-related bullying twice as frequently as White children (38.6% vs 17.7%; P = .002). Most of the caregivers (85.7%) who intervened in their child's bullying reported that it was helpful. Among parents, 17.3% reported that they were teased or bullied owing to their child's FA. More than half of the respondents (54.8%) reported that some allergens are banned from their child's school, most typically peanut. In schools banning peanuts, FA-related bullying was less frequently reported by all students who have food allergy. CONCLUSION: Bullying owing to FA is common, and caregivers, medical professionals, and school administrators can help reduce bullying by screening for bullying and supporting and educating school policies.

Clinical testing for COVID-19.

As the novel coronavirus severe acute respiratory syndrome coronavirus 2 caused coronavirus disease 2019 cases in the United States, the initial test was developed and performed at the Centers for Disease Control and Prevention. As the number of cases increased, the demand for tests multiplied, leading the Centers for Disease Control and Prevention to use the Emergency Utilization Authorization to allow clinical and commercial laboratories to develop tests to detect the presence of the virus. Many nucleic acid tests based on RT-PCR were developed, each with different techniques, specifications, and turnaround time. As the illnesses turned into a pandemic, testing became more crucial. The test supply became inadequate to meet the need and so it had to be prioritized according to guidance. For surveillance, the need for serologic tests emerged. Here, we review the timeline of test development, the turnaround times, and the various approved tests, and compare them as regards the genes they detect. We concentrate on the point-of-care tests and discuss the basis for new serologic tests. We discuss the testing guidance for prioritization and their application in a hospital setting.

Consensus report from the Food Allergy Research & Education (FARE) 2019 Oral Immunotherapy for Food Allergy Summit.

Food allergy is a major health problem affecting 5% to 10% of the population in developed nations, including an estimated 32 million Americans. Despite the large number of patients suffering from food allergies, up until the end of January 2020, no treatment for food allergies had been approved by the US Food and Drug Administration. The only options were avoidance of food allergen triggers and acute management of allergic reactions. A considerable body of data exists supporting oral immunotherapy (OIT) as a promising, novel treatment option, including that for the now Food and Drug Administration-approved peanut OIT product Palforzia (Aimmune Therapeutics, Brisbane, Calif). However, data for long-term quality-of-life improvement with OIT varies, depending on the measures used for analysis. Like many therapies, OIT is not without potential harms, and burdens, and the evaluation of patient-specific risk-benefit ratio of food OIT produces challenges for clinicians and patients alike, with many unanswered questions. Food Allergy Research & Education organized the Oral Immunotherapy for Food Allergy Summit on November 6, 2019, modeled after the PRACTALL sessions between the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma & Immunology to address these critical issues. Health care providers, patient representatives, researchers, regulators, and food allergy advocates came together to discuss OIT and identify areas of common ground as well as gaps in existing research and areas of uncertainty and disagreement. The purpose of this article was to summarize that discussion and facilitate collaboration among clinicians and patients to help them make better-informed decisions about offering and accepting OIT, respectively, as a therapeutic option.

Persistent, refractory, and biphasic anaphylaxis: A multidisciplinary Delphi study.

BACKGROUND: The use of inconsistent definitions for anaphylaxis outcomes limits our understanding of the natural history and epidemiology of anaphylaxis, hindering clinical practice and research efforts. OBJECTIVE: Our aim was to develop consensus definitions for clinically relevant anaphylaxis outcomes by utilizing a multidisciplinary group of clinical and research experts in anaphylaxis. METHODS: Using Delphi methodology, we developed agenda topics and drafted questions to review during monthly conference calls. Through online surveys, a 19-member panel consisting of experts in allergy and/or immunology and emergency medicine rated their level of agreement with the appropriateness of statements on a scale of 1 to 9. A median value of 1.0 to 3.4 was considered inappropriate, a median value of 3.5 to 6.9 was considered uncertain, and a median value of 7.0 to 9.0 was considered appropriate. A disagreement index was then calculated, with values less than 1.0 categorized as "consensus reached." If consensus was not reached after the initial survey, subsequent surveys incorporating the aggregate de-identified responses from prior surveys were sent to panel members. This process was repeated until consensus was reached or 4 survey rounds had been completed, after which the question was categorized as "no consensus reached." RESULTS: The panel developed outcome definitions for persistent, refractory, and biphasic anaphylaxis, as well as for persistent and biphasic nonanaphylactic reactions. There was also consensus among panel members regarding the need to develop an anaphylaxis severity grading system. CONCLUSION: Dissemination and application of these definitions in clinical care and research will help standardize the terminology used to describe anaphylaxis outcomes and serve as the foundation for future research, including research aimed at development of an anaphylaxis severity grading system.

Long-term, open-label extension study of the efficacy and safety of epicutaneous immunotherapy for peanut allergy in children: PEOPLE 3-year results.

BACKGROUND: The PEPITES (Peanut EPIT Efficacy and Safety) trial, a 12-month randomized controlled study of children with peanut allergy and 4 to 11 years old, previously reported the safety and efficacy of epicutaneous immunotherapy (EPIT) for peanut allergy (250 µg, daily epicutaneous peanut protein; DBV712 250 µg). OBJECTIVE: We sought to assess interim safety and efficacy of an additional 2 years of EPIT from the ongoing (5-year treatment) PEOPLE (PEPITES Open-Label Extension) study. METHODS: Subjects who completed PEPITES were offered enrollment in PEOPLE. Following an additional 2 years of daily DBV712 250 µg, subjects who had received DBV712 250 µg in PEPITES underwent month-36 double-blind, placebo-controlled food challenge with an optional month-38 sustained unresponsiveness assessment. RESULTS: Of 213 eligible subjects who had received DBV712 250 µg in PEPITES, 198 (93%) entered PEOPLE, of whom 141 (71%) had assessable double-blind, placebo-controlled food challenge at month 36. At month 36, 51.8% of subjects (73 of 141) reached an eliciting dose of ≥1000 mg, compared with 40.4% (57 of 141) at month 12; 75.9% (107 of 141) demonstrated increased eliciting dose compared with baseline; and 13.5% (19 of 141) tolerated the full double-blind, placebo-controlled food challenge of 5444 mg. Median cumulative reactive dose increased from 144 to 944 mg. Eighteen subjects underwent an optional sustained unresponsiveness assessment; 14 of those (77.8%) maintained an eliciting dose of ≥1000 mg at month 38. Local patch-site skin reactions were common but decreased over time. There was no treatment-related epinephrine use in years 2 or 3. Compliance was high (96.9%), and withdrawals due to treatment-related adverse events were low (1%). CONCLUSIONS: These results demonstrate that daily EPIT treatment for peanut allergy beyond 1 year leads to continued response from a well-tolerated, simple-to-use regimen.

Effect of Epicutaneous Immunotherapy vs Placebo on Reaction to Peanut Protein Ingestion Among Children With Peanut Allergy: The PEPITES Randomized Clinical Trial.

Importance: There are currently no approved treatments for peanut allergy. Objective: To assess the efficacy and adverse events of epicutaneous immunotherapy with a peanut patch among peanut-allergic children. Design, Setting, and Participants: Phase 3, randomized, double-blind, placebo-controlled trial conducted at 31 sites in 5 countries between January 8, 2016, and August 18, 2017. Participants included peanut-allergic children (aged 4-11 years [n = 356] without a history of a severe anaphylactic reaction) developing objective symptoms during a double-blind, placebo-controlled food challenge at an eliciting dose of 300 mg or less of peanut protein. Interventions: Daily treatment with peanut patch containing either 250 µg of peanut protein (n = 238) or placebo (n = 118) for 12 months. Main Outcomes and Measures: The primary outcome was the percentage difference in responders between the peanut patch and placebo patch based on eliciting dose (highest dose at which objective signs/symptoms of an immediate hypersensitivity reaction developed) determined by food challenges at baseline and month 12. Participants with baseline eliciting dose of 10 mg or less were responders if the posttreatment eliciting dose was 300 mg or more; participants with baseline eliciting dose greater than 10 to 300 mg were responders if the posttreatment eliciting dose was 1000 mg or more. A threshold of 15% or more on the lower bound of a 95% CI around responder rate difference was prespecified to determine a positive trial result. Adverse event evaluation included collection of treatment-emergent adverse events (TEAEs). Results: Among 356 participants randomized (median age, 7 years; 61.2% male), 89.9% completed the trial; the mean treatment adherence was 98.5%. The responder rate was 35.3% with peanut-patch treatment vs 13.6% with placebo (difference, 21.7% [95% CI, 12.4%-29.8%; P < .001]). The prespecified lower bound of the CI threshold was not met. TEAEs, primarily patch application site reactions, occurred in 95.4% and 89% of active and placebo groups, respectively. The all-causes rate of discontinuation was 10.5% in the peanut-patch group vs 9.3% in the placebo group. Conclusions and Relevance: Among peanut-allergic children aged 4 to 11 years, the percentage difference in responders at 12 months with the 250-µg peanut-patch therapy vs placebo was 21.7% and was statistically significant, but did not meet the prespecified lower bound of the confidence interval criterion for a positive trial result. The clinical relevance of not meeting this lower bound of the confidence interval with respect to the treatment of peanut-allergic children with epicutaneous immunotherapy remains to be determined. Trial Registration: ClinicalTrials.gov Identifier: NCT02636699.

Addendum guidelines for the prevention of peanut allergy in the United States: Report of the National Institute of Allergy and Infectious Diseases-sponsored expert panel.

BACKGROUND: Food allergy is an important public health problem because it affects children and adults, can be severe and even life-threatening, and may be increasing in prevalence. Beginning in 2008, the National Institute of Allergy and Infectious Diseases, working with other organizations and advocacy groups, led the development of the first clinical guidelines for the diagnosis and management of food allergy. A recent landmark clinical trial and other emerging data suggest that peanut allergy can be prevented through introduction of peanut-containing foods beginning in infancy. OBJECTIVES: Prompted by these findings, along with 25 professional organizations, federal agencies, and patient advocacy groups, the National Institute of Allergy and Infectious Diseases facilitated development of addendum guidelines to specifically address the prevention of peanut allergy. RESULTS: The addendum provides 3 separate guidelines for infants at various risk levels for the development of peanut allergy and is intended for use by a wide variety of health care providers. Topics addressed include the definition of risk categories, appropriate use of testing (specific IgE measurement, skin prick tests, and oral food challenges), and the timing and approaches for introduction of peanut-containing foods in the health care provider's office or at home. The addendum guidelines provide the background, rationale, and strength of evidence for each recommendation. CONCLUSIONS: Guidelines have been developed for early introduction of peanut-containing foods into the diets of infants at various risk levels for peanut allergy.

Addendum guidelines for the prevention of peanut allergy in the United States: Report of the National Institute of Allergy and Infectious Diseases-sponsored expert panel.

BACKGROUND: Food allergy is an important public health problem because it affects children and adults, can be severe and even life-threatening, and may be increasing in prevalence. Beginning in 2008, the National Institute of Allergy and Infectious Diseases, working with other organizations and advocacy groups, led the development of the first clinical guidelines for the diagnosis and management of food allergy. A recent landmark clinical trial and other emerging data suggest that peanut allergy can be prevented through introduction of peanut-containing foods beginning in infancy. OBJECTIVES: Prompted by these findings, along with 25 professional organizations, federal agencies, and patient advocacy groups, the National Institute of Allergy and Infectious Diseases facilitated development of addendum guidelines to specifically address the prevention of peanut allergy. RESULTS: The addendum provides 3 separate guidelines for infants at various risk levels for the development of peanut allergy and is intended for use by a wide variety of health care providers. Topics addressed include the definition of risk categories, appropriate use of testing (specific IgE measurement, skin prick tests, and oral food challenges), and the timing and approaches for introduction of peanut-containing foods in the health care provider's office or at home. The addendum guidelines provide the background, rationale, and strength of evidence for each recommendation. CONCLUSIONS: Guidelines have been developed for early introduction of peanut-containing foods into the diets of infants at various risk levels for peanut allergy.

Addendum Guidelines for the Prevention of Peanut Allergy in the United States: Report of the National Institute of Allergy and Infectious Diseases-Sponsored Expert Panel.

BACKGROUND: Food allergy is an important public health problem because it affects children and adults, can be severe and even life-threatening, and may be increasing in prevalence. Beginning in 2008, the National Institute of Allergy and Infectious Diseases, working with other organizations and advocacy groups, led the development of the first clinical guidelines for the diagnosis and management of food allergy. A recent landmark clinical trial and other emerging data suggest that peanut allergy can be prevented through introduction of peanut-containing foods beginning in infancy. OBJECTIVES: Prompted by these findings, along with 25 professional organizations, federal agencies, and patient advocacy groups, the National Institute of Allergy and Infectious Diseases facilitated development of addendum guidelines to specifically address the prevention of peanut allergy. RESULTS: The addendum provides three separate guidelines for infants at various risk levels for the development of peanut allergy and is intended for use by a wide variety of health care providers. Topics addressed include the definition of risk categories, appropriate use of testing (specific IgE measurement, skin prick tests, and oral food challenges), and the timing and approaches for introduction of peanut-containing foods in the health care provider's office or at home. The addendum guidelines provide the background, rationale, and strength of evidence for each recommendation. CONCLUSIONS: Guidelines have been developed for early introduction of peanut-containing foods into the diets of infants at various risk levels for peanut allergy.

Defects of B-cell terminal differentiation in patients with type-1 Kabuki syndrome.

BACKGROUND: Kabuki syndrome (KS) is a complex multisystem developmental disorder associated with mutation of genes encoding histone-modifying proteins. In addition to craniofacial, intellectual, and cardiac defects, KS is also characterized by humoral immune deficiency and autoimmune disease, yet no detailed molecular characterization of the KS-associated immune phenotype has been reported. OBJECTIVE: We sought to characterize the humoral immune defects found in patients with KS with lysine methyltransferase 2D (KMT2D) mutations. METHODS: We comprehensively characterized B-cell function in a cohort (n = 13) of patients with KS (age, 4 months to 27 years). RESULTS: Three quarters (77%) of the cohort had a detectable heterozygous KMT2D mutation (50% nonsense, 20% splice site, and 30% missense mutations), and 70% of the reported mutations are novel. Among the patients with KMT2D mutations (KMT2D(Mut/+)), hypogammaglobulinemia was detected in all but 1 patient, with IgA deficiency affecting 90% of patients and a deficiency in at least 1 other isoform seen in 40% of patients. Numbers of total memory (CD27(+)) and class-switched memory B cells (IgM(-)) were significantly reduced in patients with KMT2D(Mut/+) mutations compared with numbers in control subjects (P < .001). Patients with KMT2D(Mut/+) mutations also had significantly reduced rates of somatic hypermutation in IgG (P = .003) but not IgA or IgM heavy chain sequences. Impaired terminal differentiation was noted in primary B cells from patients with KMT2D(Mut/+) mutations. Autoimmune pathology was observed in patients with missense mutations affecting the SET domain and its adjacent domains. CONCLUSIONS: In patients with KS, autosomal dominant KMT2D mutations are associated with dysregulation of terminal B-cell differentiation, leading to humoral immune deficiency and, in some cases, autoimmunity. All patients with KS should undergo serial clinical immune evaluations.