Novel mutation and expanding phenotype in IRF2BP2 deficiency.

Inborn errors of immunity manifest with susceptibility to infection but may also present with immune dysregulation only. According to the European Society for Immunodeficiencies Registry about 50% of inborn errors of immunity are classified as common variable immunodeficiencies (CVID). In only few CVID patients are monogenic causes identified. IFN regulatory factor-2 binding protein 2 (IRF2BP2) is one of 20 known genes associated with CVID phenotypes and has only been reported in two families so far. We report another IRF2BP2-deficient patient with a novel pathogenic variant and phenotype and characterize impaired B cell function and immune dysregulation. We performed trio whole-exome sequencing, determined B cell subpopulations and intracellular calcium mobilization upon B cell receptor crosslinking in B cells. T cell subpopulations, T cell proliferation and a type I IFN signature were measured. Colonoscopy and gastroduodenoscopy including histopathology were performed. The 33-year-old male presented with recurrent respiratory infections since childhood, colitis and RA beginning at age 25 years. We identified a novel de novo nonsense IRF2BP2 variant c.1618C>T; p.(Q540*). IgG deficiency was detected as consequence of a severe B cell differentiation defect. This was confirmed by impaired plasmablast formation upon stimulation with CpG. No serum autoantibodies were detected. Intracellular cytokine production in CD4+ T cells and CTLA4 expression on FOXP3+ Tregs were impaired. Type I IFN signature was elevated. The identified loss-of-function variant in IRF2BP2 severely impairs B cell development and T cell homeostasis, and may be associated with colitis and RA. Our results provide further evidence for association of IRF2BP2 with CVID and contribute to the understanding of the underlying pathomechanisms. © The Author(s) 2022. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Citation

Julia Körholz, Anastasia Gabrielyan, Henrike Lisa Sczakiel, Livia Schulze, Manuela Rejzek, Martin W Laass, Nicolai Leuchten, Oliver Tiebel, Diana Aust, Karsten Conrad, Nadja Röber, Eva-Maria Jacobsen, Nadja Ehmke, Reinhard Berner, Nadja Lucas, Minae A Lee-Kirsch, Ralf Wiedemuth, Joachim Roesler, Axel Roers, Timm Amendt, Catharina Schuetz. Novel mutation and expanding phenotype in IRF2BP2 deficiency. Rheumatology (Oxford, England). 2023 Apr 03;62(4):1699-1705

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PMID: 36193988

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