Detailed genotype-phenotype analysis of AOSD cohorts

Adult-onset Still’s disease (AOSD) is systemic autoinflammatory disorder of unknown aetiology. Various genetic and environmental factors have been implicated in its pathogenies, but the genetic studies so far have been limited to few selected genes of interest. We conducted detailed genetic analysis of a large cohort of patients with AOSD, using deep whole exome sequencing to identify rare germline variants and somatic mutations of interest. In parallel, we conducted a comprehensive inflammatory marker profiling from the patients’ sera. We used a bespoke assay to detect NLRP3 inflammasome activation and novel method to measure Type I Interferon (IFN) score. We found a strong genetic connection between AOSD and the presence of rare germline variants and somatic mutations within genes associated with monogenic autoinflammatory disorders and clonal haematopoiesis of unknown significance. Profiling of inflammatory markers showed significantly elevated ASC/NLRP3 speck levels in AOSD compared to healthy controls, whilst cytokine analysis identified several significantly elevated cytokines including IL-18, IL-6, IL-23, IFN and IFN-2. The Type I IFN score was also significantly higher in AOSD compared to healthy and some disease controls. We did not find any correlation between rare genetic variants and somatic mutation burden with selected inflammatory markers (ASC/NLRP3 speck, ASC speck, IL-1IL-18, IL-6 and Type I IFN score). Our study demonstrated considerable genetic complexity within AOSD. Many enriched variants may not be sufficient, individually to cause disease but more likely to contribute to a multiple-hit model for AOSD.