Mutations in genes encoding proteins that are involved in mitochondrial heme synthesis, iron-sulfur cluster biogenesis, and mitochondrial protein synthesis have previously been implicated in the pathogenesis of the congenital sideroblastic anemias (CSAs). We recently described a syndromic form of CSA associated with B-cell immunodeficiency, periodic fevers, and developmental delay (SIFD). Here we demonstrate that SIFD is caused by biallelic mutations in TRNT1, the gene encoding the CCA-adding enzyme essential for maturation of both nuclear and mitochondrial transfer RNAs. Using budding yeast lacking the TRNT1 homolog, CCA1, we confirm that the patient-associated TRNT1 mutations result in partial loss of function of TRNT1 and lead to metabolic defects in both the mitochondria and cytosol, which can account for the phenotypic pleiotropy

Key Points A novel clinical syndrome of CSA, B-cell immunodeficiency, periodic fevers, and developmental delay is described. Bone marrow transplant resulted in complete and durable resolution of the hematologic and immunologic manifestations.

We conclude that the lack of phagocyte-derived oxidative burst is associated with spontaneous autoimmunity and linked with type I IFN signature in both mice and humans.

Significance There is growing evidence that preexisting autoantibodies neutralizing type I interferons (IFNs) are strong determinants of life-threatening COVID-19 pneumonia. It is important to estimate their quantitative impact on COVID-19 mortality upon SARS-CoV-2 infection, by age and sex, as both the prevalence of these autoantibodies and the risk of COVID-19 death increase with age and are higher in men. Using an unvaccinated sample of 1,261 deceased patients and 34,159 individuals from the general population, we found that autoantibodies against type I IFNs strongly increased the SARS-CoV-2 infection fatality rate at all ages, in both men and women. Autoantibodies against type I IFNs are strong and common predictors of life-threatening COVID-19. Testing for these autoantibodies should be considered in the general population.

HSV-1 encephalitis (HSE) is typically sporadic. Inborn errors of TLR3-and DBR1-mediated central nervous system (CNS) cell-intrinsic immunity can account for forebrain and brainstem HSE, respectively. We report five unrelated patients with forebrain HSE, each heterozygous for one of four rare variants of SNORA31, encoding a snoRNA of the H/ACA class that are predicted to direct the isomerization of uridine residues to pseudouridine in snRNA and rRNA. We show that CRISPR/Cas9-introduced biallelic and monoallelic SNORA31 deletions render human pluripotent stem cells (hPSCs)-derived cortical neurons susceptible to HSV-1. Accordingly, SNORA31mutated patient hPSCs-derived cortical neurons are susceptible to HSV-1, like those from TLR3or STAT1-deficient patients. Exogenous IFN-β renders SNORA31and TLR3but not STAT1-Lafaille et al.