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Background: Dominant negative STAT3 loss-of-function is the most common genetic cause of hyper-IgE syndrome (HIES). Patients may present with a host of both immune and non-immune manifestations, including connective tissue abnormalities, recurrent infections, malignant predisposition, and biochemical evidence of elevated serum IgE or eosinophilia. Aim: To describe a novel splice-site variant in STAT3 resulting in HIES. Methods: Case report of two family members with HIES. Results: A proband and his son presented with neonatal-onset pustular rash, recurrent skin and sinopulmonary infections and elevated serum IgE and were diagnosed with AD-HIES. They were identified to harbor a novel splice-site variant in the DNA-binding domain (DBD) of STAT3: c.1110-3C>G, predicted to result in defective splicing in exon 12. Interestingly, a number of other patients with AD-HIES have mutations affecting the same splice-site, suggesting this may be a hot-spot for mutagenesis. Conclusion: Splice-site mutations in the DBD of STAT3 are increasingly identified as a cause of AD-HIES. Future work is required to delineate whether patients with splice-site mutations have unique clinical characteristics, supporting efforts for genotype-phenotype correlation in this disease. Statement of Novelty: We present a novel splice-site mutation in the DNA-binding domain of STAT3 leading to autosomal dominant hyper-IgE syndrome.

Background: Since the onset of the COVID-19 pandemic, a main challenge for clinicians and public health decision-makers has revolved around risk stratification in vulnerable populations, in particular individuals with inborn errors of immunity (IEI). However, available reports of the clinical course of COVID-19 in patients with IEI show wide variability, from a complete lack of symptoms to severe and complicated disease. Objective: To present the clinical features and outcomes of SARS-CoV-2 infection in adult patients with IEI. Methods: We performed a retrospective chart review documenting patient characteristics and clinical course of SARS-CoV-2 infection between December 2021 and July 2022. Results: Ten adult patients with IEI followed in our center were diagnosed with COVID-19, as determined by RT-PCR or rapid antigen testing. IEI in this cohort included those with humoral and combined immunodeficiencies, as well as phagocytic defects. An underlying lung comorbidity was identified in 3 patients. Symptoms were mostly mild and self-limiting, and no severe outcomes, complications, or mortality were noted in this study. Conclusions: We suggest that patients affected by a wide range of both humoral and combined IEI may demonstrate resilience, while highlighting the possible protective effects of vaccination and immunoglobulin replacement in this population. Statement of Novelty: We report on the mild COVID-19 clinical course of 10 adults with IEI.

MECP2 duplication syndrome (MDS) is a neurodevelopmental disorder caused by tandem duplication of theMECP2locus and its surrounding genes, includingIRAK1. Current MDS mouse models involve transgenic expression ofMECP2only, limiting their applicability to the study of the disease. Herein, we show that an efficient and precise CRISPR/Cas9 fusion proximity-based approach can be utilized to generate anIrak1-Mecp2tandem duplication mouse model. TheMecp2 Dupmodel displays a neurological phenotype in keeping with MDS and demonstrates an abnormal immune response to infection not previously observed in other mouse models, possibly stemming from concurrentIrak1overexpression. TheMecp2 Dupmouse line thus provides an innovative tool to investigate disease mechanisms and potential therapeutic development.

Introduction: The phosphoinositide 3-kinase (PI3K) pathway plays critical roles in diverse cellular processes, including differentiation, proliferation, motility, survival, and growth. PI3Kδ, comprised of the catalytic subunit p110δ and regulatory subunit p85α, is essential for normal lymphocyte and myeloid development and function. Gain-of-function mutations in PIK3CD (encoding p110δ) cause a combined immunodeficiency known as activated PI3Kδ syndrome (APDS), in which patients frequently present with recurrent respiratory infections, severe recurrent (or persistent) infections with herpes family viruses, and lymphadenopathy. Aim: To describe the clinical presentation, immune evaluation, and genetic work-up of 2 patients (daughter and mother) with recurrent sinopulmonary, soft tissue, and skin infections. Results: Both daughter and mother presented with recurrent sinopulmonary and soft tissue infections. Immune evaluation of the daughter revealed intermittent hypogammaglobulinemia and abnormal specific vaccine responses, while immune parameters of her mother were normal. Whole exome sequencing identified a novel mutation in PIK3CD (NM_005026), c.C719T, resulting in p.T240M. Western blot analysis of downstream AKT levels revealed increased basal phosphorylation, in line with gain-of-function mutations of PIK3CD. Conclusion: The novel missense mutation in PIK3CD occurs in the region encoding the Ras-binding domain (RBD) of p110δ, and likely alters the structural configuration of the domain. To date, pathogenic mutations targeting the RBD of p110δ have not yet been described. Our results expand on the genotypic spectrum of APDS. Statement of Novelty: We describe a novel mutation in the Ras-binding domain of PIK3CD leading to a presentation of recurrent sinopulmonary and soft tissue infections in the context of APDS.

In more than one-third of primary immunodeficiency (PID) patients, extensive genetic analysis including whole-exome sequencing (WES) fails to identify the genetic defect. Whole-genome sequencing (WGS) is able to detect variants missed by other genomics platforms, enabling the molecular diagnosis of otherwise unresolved cases. Here, we report two siblings, offspring of consanguineous parents, who experienced similar severe events encompassing early onset of colitis, lymphoproliferation, and hypogammaglobulinemia, typical of lipopolysaccharide-responsive and beige-like anchor (LRBA) or cytotoxic T lymphocyte antigen 4 (CTLA4) deficiencies. Gene-panel sequencing, comparative genomic hybridization (CGH) array, and WES failed to reveal a genetic aberration in relevant genes. WGS of these patients detected a 12.3 kb homozygous tandem duplication that was absent in control cohorts and is predicted to disrupt the reading frame of the LRBA gene. The variant was validated by PCR and Sanger sequencing, demonstrating the presence of the junction between the reference and the tandem-duplicated sequence. Droplet digital PCR (ddPCR) further confirmed the copy number in the unaffected parents (CN = 3, heterozygous) and affected siblings (CN = 4, homozygous), confirming the expected segregation pattern. In cases of suspected inherited immunodeficiency, WGS may reveal a mutation when other methods such as microarray and WES analysis failed to detect an aberration.

BACKGROUND STAT1 gain-of-function (GOF) is an immune dysregulatory disorder with poorly studied genotype-phenotype correlation, impeding prognostication and early intervention. Given previous mechanistic studies, as well as anecdotal clinical reports, we sought to systematically determine whether DNA-binding domain (DBD) mutations in STAT1 result in a different phenotype than mutations in other gene domains. METHODS Negative prognostic features previously identified by the International STAT1 GOF Study Group (invasive infections, intracranial aneurysms, and malignancy), as well as other clinical features and mortality, were compared within a cohort of 30 patients with STAT1 GOF diagnosed at our center, consisting of 9 patients with DBD mutations and 21 patients with non-DBD mutations. We subsequently re-analyzed mortality data from a large, previously-published 274-patient cohort by the International STAT1 GOF Study Group. RESULTS While no differences were noted with respect to malignancy or symptomatic aneurysms, invasive /opportunistic infections were substantially more common among DBD patients, as were sinopulmonary infections, bronchiectasis, enteropathy, endocrinopathies, lymphoproliferative manifestations, and recurrent fevers/HLH. DBD patients also had a lower probability of survival and younger age of mortality compared with non-DBD patients. Our re-evaluation of the published data from the International STAT1 GOF Study Group revealed a similar finding of earlier mortality among patients harboring DBD mutations. CONCLUSION We report that STAT1 GOF patients with DBD mutations may be regarded as a unique subgroup, impacted more by early-onset profound combined immunodeficiency and with earlier mortality. These findings may impact clinical decision making with respect to early intervention, and in particular hematopoietic stem cell transplant considerations, in such patients.