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Objective: Primary antiphospholipid syndrome (PAPS) is a rare autoimmune disease characterized by the presence of antiphospholipid antibodies and the occurrence of thrombotic events and pregnancy complications. Our study aimed to identify novel genetic susceptibility loci associated with PAPS. Methods: We performed a genome‐wide association study comprising 5,485 individuals (482 affected individuals) of European ancestry. Significant and suggestive independent variants from a meta‐analysis of approximately 7 million variants were evaluated for functional and biological process enrichment. The genetic risk variability for PAPS in different populations was also assessed. Hierarchical clustering, Mahalanobis distance, and Dirichlet Process Mixtures with uncertainty clustering methods were used to assess genetic similarities between PAPS and other immune‐mediated diseases. Results: We revealed genetic associations with PAPS in a regulatory locus within the HLA class II region near HLA‐DRA and in STAT1‐STAT4 with a genome‐wide level of significance; 34 additional suggestive genetic susceptibility loci for PAPS were also identified. The disease risk allele near HLA‐DRA is associated with overexpression of HLA‐DRB6, HLA‐DRB9, HLA‐DQA2, and HLA‐DQB2 in immune cells, vascular tissue, and nervous tissue. This association is independent of the association between PAPS and HLA‐DRB1*1302. Functional analyses highlighted immune‐related pathways in PAPS‐associated loci. The comparison with other immune‐mediated diseases revealed a close genetic relatedness to neuromyelitis optica, systemic sclerosis, and Sjögren syndrome, suggesting co‐localized causal variations close to STAT1‐STAT4, TNPO3, and BLK. Conclusion: This study represents a comprehensive large‐scale genetic analysis for PAPS and provides new insights into the genetic basis and pathophysiology of this rare disease. [ABSTRACT FROM AUTHOR]

Objective: The biologic diagnosis of primary Sjögren disease (SjD) mainly relies on anti‐Ro60/SSA antibodies, whereas the significance of anti‐Ro52/TRIM21 antibodies currently remains unclear. The aim of this study was to characterize the clinical, serological, biologic, transcriptomic, and interferon profiles of patients with SjD according to their anti‐Ro52/TRIM21 antibody status. Methods: Patients with SjD from the European PRECISESADS (n = 376) and the Brittany Diagnostic Suspicion of primitive Sjögren's Syndrome (DIApSS); (n = 146) cohorts were divided into four groups: double negative (Ro52−/Ro60−), isolated anti‐Ro52/TRIM21 positive (Ro52+), isolated anti‐Ro60/SSA positive (Ro60+), and double‐positive (Ro52+/Ro60+) patients. Clinical information; EULAR Sjögren Syndrome Disease Activity Index, a score representing systemic activity; and biologic markers associated with disease severity were evaluated. Transcriptome data obtained from whole blood by RNA sequencing and type I and II interferon signatures were analyzed for PRECISESADS patients. Results: In the DIApSS cohort, Ro52+/Ro60+ patients showed significantly more parotidomegaly (33.3% vs 0%–11%) along with higher β2‐microglobulin (P = 0.0002), total immunoglobulin (P < 0.0001), and erythrocyte sedimentation rate levels (P = 0.002) as well as rheumatoid factor (RF) positivity (66.2% vs 20.8%–25%) compared to other groups. The PRECISESADS cohort corroborated these observations, with increased arthritis (P = 0.046), inflammation (P = 0.005), hypergammaglobulinemia (P < 0.0001), positive RF (P < 0.0001), leukopenia (P = 0.004), and lymphopenia (P = 0.009) in Ro52+/Ro60+ patients. Cumulative EULAR Sjögren Syndrome Disease Activity Index results further confirmed these disparities (P = 0.002). Transcriptome analysis linked anti‐Ro52/TRIM21 antibody positivity to interferon pathway activation as an underlying cause for these clinical correlations. Conclusion: These results suggest that the combination of anti‐Ro52/TRIM21 and anti‐Ro60/SSA antibodies is associated with a clinical, biologic, and transcriptional profile linked to greater disease severity in SjD through the potentiation of the interferon pathway activation by anti‐Ro52/TRIM21 antibodies. [ABSTRACT FROM AUTHOR]