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Objective: Deficiency of adenosine deaminase 2 (DADA2) is a monogenic form of vasculitis that can resemble polyarteritis nodosa (PAN). This study was undertaken to identify potential disease-causing sequence variants in ADA2 in patients with idiopathic PAN, granulomatosis with polyangiitis (GPA), or microscopic polyangiitis (MPA)., Methods: Patients with idiopathic PAN (n = 118) and patients with GPA or MPA (n = 1,107) were screened for rare nonsynonymous variants in ADA2 using DNA sequencing methods. ADA-2 enzyme activity was assessed in selected serum samples., Results: Nine of 118 patients with PAN (7.6%) were identified as having rare nonsynonymous variants in ADA2. Four patients (3.4%) were biallelic for pathogenic or likely pathogenic variants, and 5 patients (4.2%) were monoallelic carriers for 3 variants of uncertain significance and 2 likely pathogenic variants. Serum samples from 2 patients with PAN with biallelic variants were available and showed markedly reduced ADA-2 enzyme activity. ADA-2 enzyme testing of 86 additional patients revealed 1 individual with strongly reduced ADA-2 activity without detectable pathogenic variants. Patients with PAN and biallelic variants in ADA2 were younger at diagnosis than patients with 1 or no variant in ADA2, with no other clinical differences noted. None of the patients with GPA or MPA carried biallelic variants in ADA2., Conclusion: A subset of patients with idiopathic PAN meet genetic criteria for DADA2. Given that tumor necrosis factor inhibition is efficacious in DADA2 but is not conventional therapy for PAN, these findings suggest that ADA-2 testing should strongly be considered in patients with hepatitis B virus-negative idiopathic PAN., (© 2020 American College of Rheumatology. This article has been contributed to by US Government employees and their work is in the public domain in the USA.)

Objective: To identify risk alleles relevant to the causal and biologic mechanisms of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV)., Methods: A genome-wide association study and subsequent replication study were conducted in a total cohort of 1,986 cases of AAV (patients with granulomatosis with polyangiitis [Wegener's] [GPA] or microscopic polyangiitis [MPA]) and 4,723 healthy controls. Meta-analysis of these data sets and functional annotation of identified risk loci were performed, and candidate disease variants with unknown functional effects were investigated for their impact on gene expression and/or protein function., Results: Among the genome-wide significant associations identified, the largest effect on risk of AAV came from the single-nucleotide polymorphism variants rs141530233 and rs1042169 at the HLA-DPB1 locus (odds ratio [OR] 2.99 and OR 2.82, respectively) which, together with a third variant, rs386699872, constitute a triallelic risk haplotype associated with reduced expression of the HLA-DPB1 gene and HLA-DP protein in B cells and monocytes and with increased frequency of complementary proteinase 3 (PR3)-reactive T cells relative to that in carriers of the protective haplotype. Significant associations were also observed at the SERPINA1 and PTPN22 loci, the peak signals arising from functionally relevant missense variants, and at PRTN3, in which the top-scoring variant correlated with increased PRTN3 expression in neutrophils. Effects of individual loci on AAV risk differed between patients with GPA and those with MPA or between patients with PR3-ANCAs and those with myeloperoxidase-ANCAs, but the collective population attributable fraction for these variants was substantive, at 77%., Conclusion: This study reveals the association of susceptibility to GPA and MPA with functional gene variants that explain much of the genetic etiology of AAV, could influence and possibly be predictors of the clinical presentation, and appear to alter immune cell proteins and responses likely to be key factors in the pathogenesis of AAV., (© 2016 The Authors. Arthritis & Rheumatology published by Wiley Periodicals, Inc. on behalf of American College of Rheumatology.)

Objective: Interleukin-6 (IL-6) is a pivotal cytokine in the pathogenesis of polymyalgia rheumatica (PMR), yet the efficacy of IL-6 blockade with tocilizumab (TCZ) for the treatment of PMR is unknown. The aim of this study was to assess the efficacy and safety of TCZ in newly diagnosed PMR., Methods: In a single-center open-label study, patients with newly diagnosed PMR who had been treated with glucocorticoids (GCs) for <1 month were treated monthly with intravenous (IV) TCZ 8 mg/kg for 1 year, with a rapid tapering of GCs according to standardized protocol. The primary end point was the proportion of patients in relapse-free remission without GC treatment at 6 months. Secondary outcome measures included duration of GC use and cumulative GC dose. Patients were followed up for 15 months., Results: Ten patients were enrolled in the study. One patient withdrew after 2 months, leaving 9 patients in whom the primary end point was assessed. The primary end point of relapse-free remission without GC treatment at 6 months was achieved by all 9 of these patients. All patients who received TCZ treatment were able to discontinue GCs within 4 months of study entry. The cumulative mean ± SD prednisone dose was 1,085 ± 301 mg and the total duration of GC exposure was 3.9 ± 0.9 months. Remission persisted without relapse, in all 9 patients, throughout the entire 15-month study., Conclusion: Our findings suggest that TCZ may be an effective, safe, and well-tolerated treatment for newly diagnosed patients with PMR, with a robust steroid-sparing effect., (© 2016, American College of Rheumatology.)