Background The genetic etiologies of the hyper-IgE syndromes are diverse. Approximately 60-70% of patients with hyper-IgE syndrome have dominant mutations in STAT3, and a single patient was reported to have a homozygous TYK2 mutation. In the remaining hyper-IgE syndrome patients, the genetic etiology has not yet been identified. Methods We performed genome-wide single nucleotide polymorphism analysis for nine subjects with autosomal recessive hyper-IgE syndrome to locate copy number variations and homozygous haplotypes. Homozygosity mapping was performed with twelve subjects from seven additional families. The candidate gene was analyzed by genomic and cDNA sequencing to identify causative alleles in a total of 27 patients with autosomal recessive hyper-IgE syndrome. Findings Subtelomeric microdeletions were identified in six subjects at the terminus of chromosome 9p. In all patients the deleted interval involved DOCK8, encoding a protein implicated in the regulation of the actin cytoskeleton. Sequencing of subjects without large deletions revealed 16 patients from nine unrelated families with distinct homozygous mutations in DOCK8 causing premature termination, frameshift, splice site disruption, single exon- and micro-deletions. DOCK8 deficiency was associated with impaired activation of CD4+ and CD8+ T cells. Interpretation Autosomal recessive mutations in DOCK8 are responsible for many, though not all, cases of autosomal recessive hyper-IgE syndrome. DOCK8 disruption is associated with a phenotype of severe cellular immunodeficiency characterized by susceptibility to viral infections, atopic eczema, defective T cell activation and TH17 cell differentiation; and impaired eosinophil homeostasis and dysregulation of IgE.

Most autosomal genetic causes of childhood-onset hypogammaglobulinemia are currently not well understood. Most affected individuals are simplex cases, but both autosomal-dominant and autosomal-recessive inheritance have been described. We performed genetic linkage analysis in consanguineous families affected by hypogammaglobulinemia. Four consanguineous families with childhood-onset humoral immune deficiency and features of autoimmunity shared genotype evidence for a linkage interval on chromosome 4q. Sequencing of positional candidate genes revealed that in each family, affected individuals had a distinct homozygous mutation in LRBA (lipopolysaccharide responsive beige-like anchor protein). All LRBA mutations segregated with the disease because homozygous individuals showed hypogammaglobulinemia and autoimmunity, whereas heterozygous individuals were healthy. These mutations were absent in healthy controls. Individuals with homozygous LRBA mutations had no LRBA, had disturbed B cell development, defective in vitro B cell activation, plasmablast formation, and immunoglobulin secretion, and had low proliferative responses. We conclude that mutations in LRBA cause an immune deficiency characterized by defects in B cell activation and autophagy and by susceptibility to apoptosis, all of which are associated with a clinical phenotype of hypogammaglobulinemia and autoimmunity.

Highlights1. What is already known about this topic? SARS-CoV-2 causes asymptomatic or mild infection in about 80% of humans, while an excessive immune response has killed millions. Differential susceptibility and risk factors became a concern early in the pandemic. Several monogenic defects that involve innate viral sensors or affect interferon response pathways, as well as autoantibodies against type 1 interferons, have been identified in 14% of patients with life-threatening COVID-19. The impact of the novel betacoronavirus infection in patients with known inborn errors of immunity is less clear. Case series and reports from different countries have suggested a minor impact or even a potential protective effect of the IEI for some patients.2. What does this article add to our knowledge? We describe findings and outcomes of COVID-19 in 31 pediatric and adult patients with known IEI from Mexico, 84% of whom survived. Pediatric patients had a higher hospitalization rate. Inpatient mortality was 40%, and ICU mortality was 63%. Six patients died of secondary bacterial infection or uncontrolled systemic inflammation, but not from overwhelming viral infection. One patient with an autoinflammatory disorder under treatment with anakinra had a catastrophic clinical course. Eighty percent of patients received IVIG as part of their treatment for acute SARS-CoV-2 infection.3. How does this study impact current management guidelines? We recommend continued and/or high-dose IVIG in patients with known IEI seeking care for COVID-19. Patients with autoinflammatory disorders, especially those with inflammasome dysregulation, should probably take extreme measures to prevent exposure, while doctors taking care of SARS-CoV-2 infected patients with immune deficiencies must do everything they can to prevent secondary bacterial infections. The high survival of patients with COVID-19 in the context of inborn errors of immunity worldwide (over 80%) might be the result of patientphysician awareness and special care.