Sawalha, Amr H.

Objective Gain‐of‐function variants in IDH1 and IDH2 are enriched among individuals with coexisting myeloid neoplasms and autoimmune diseases. However, the association between IDH1 / IDH2 variants and rheumatic diseases independent of hematologic neoplasms remains unclear. We investigated the association between rare gain‐of‐function and loss‐of‐function genetic variants in IDH1 and IDH2 and immune‐mediated rheumatic diseases. Methods Individuals with gain‐of‐function and loss‐of‐function variants in IDH1/IDH2 were identified by whole genome sequencing in the UK Biobank and the All of Us Research Program. These individuals were matched 1:10 to controls without IDH1 or IDH2 variants by age, sex, and ancestry. The frequency of immune‐mediated rheumatic diseases in the presence and absence of IDH1/IDH2 variants was compared using chi‐square or Fisher exact tests. Results Fifty‐five individuals with IDH1 or IDH2 gain‐of‐function variants without pre‐existing hematologic neoplasms were identified in the UK Biobank. These individuals had a significantly higher frequency of incident immune‐mediated rheumatic diseases compared to matched controls (11 of 55 [20%] vs 20 of 550 [4%], odds ratio [OR] = 6.6, P = 2.7 × 10 −5 ), mainly polymyalgia rheumatica (6 of 11) and rheumatoid arthritis (5 of 11). Replication in the All of Us cohort identified 65 individuals with gain‐of‐function variants and confirmed an increased odds of incident immune‐mediated rheumatic diseases compared to controls (OR = 7.7, P < 5 × 10 −4 ), predominantly rheumatoid arthritis. There was no association between loss‐of‐function variants in IDH1/IDH2 and immune‐mediated rheumatic diseases in either cohort. Conclusion Rare gain‐of‐function variants in IDH1 / IDH2 are associated with increased risk of immune‐mediated rheumatic diseases, particularly rheumatoid arthritis and polymyalgia rheumatica. image

Objective Takayasu arteritis is a rare large vessel vasculitis with incompletely understood etiology. This study was undertaken to perform the first unbiased genome‐wide association analysis of Takayasu arteritis. Methods Two independent cohorts of patients with Takayasu arteritis from Turkey and North America were included in our study. The Turkish cohort consisted of 559 patients and 489 controls, and the North American cohort consisted of 134 patients and 1,047 controls of European ancestry. Genotyping was performed using the Omni1‐Quad and Omni2.5 genotyping arrays. Genotyping data were subjected to rigorous quality control measures and subsequently analyzed to discover genetic susceptibility loci for Takayasu arteritis. Results We identified genetic susceptibility loci for Takayasu arteritis with a genome‐wide level of significance in IL6 (rs2069837) (odds ratio [OR] 2.07, P = 6.70 × 10 −9 ), RPS9 / LILRB3 (rs11666543) (OR 1.65, P = 2.34 × 10 −8 ), and an intergenic locus on chromosome 21q22 (rs2836878) (OR 1.79, P = 3.62 × 10 −10 ). The genetic susceptibility locus in RPS9 / LILRB3 lies within the leukocyte receptor complex gene cluster on chromosome 19q13.4, and the disease risk variant in this locus correlates with reduced expression of multiple genes including the inhibitory leukocyte immunoglobulin‐like receptor gene LILRB3 ( P = 2.29 × 10 −8 ). In addition, we identified candidate susceptibility genes with suggestive levels of association ( P < 1 × 10 −5 ) with Takayasu arteritis, including PCSK5, LILRA3, PPM1G/NRBP1 , and PTK2B . Conclusion Our findings indicate novel genetic susceptibility loci for Takayasu arteritis and uncover potentially important aspects of the pathophysiology of this form of vasculitis.