Novel genetic insights: Mendelian randomization implicates Felty Syndrome in atrial fibrillation risk

Atrial fibrillation (AF) is a common and increasing arrhythmia posing major public health challenges. While management has improved, long-term efficacy and safety remain limited. Felty Syndrome, a severe rheumatoid arthritis (RA) subtype with splenomegaly and neutropenia, offers a chance to examine the autoimmune inflammation-AF link.

We employed five Mendelian randomization (MR) approaches using genome-wide association study (GWAS) data to investigate whether Felty Syndrome causes AF.

We analyzed data from the FinnGen biobank and a separate AF GWAS, selecting 17 independent SNPs as genetic instruments. We applied five MR methods, including inverse-variance weighted and MR-Egger, to estimate causal effects. Although no statistical significance was observed (e.g., weighted median beta = 0.028, P = 0.064; weighted mode beta = 0.033, P = 0.077; IVW beta = 0.021, P = 0.086; simple mode beta = 0.039, P = 0.087), a consistent trend suggested Felty Syndrome may increase AF risk. Sensitivity analyses showed robust results, with no significant heterogeneity or pleiotropy. In summary, while statistical significance was not achieved, our findings indicate a potential biological association that merits further investigation.

This study highlights the need to identify new risk factors to improve AF prevention and management. The lack of significance may reflect a common challenge in MR studies of rare exposures like Felty Syndrome, where weak instruments can dilute causal estimates. Future research requires larger genetic datasets and should investigate the underlying molecular mechanisms for targeted therapies. Key Points • This study first applies Mendelian randomization to explore the Felty Syndrome-atrial fibrillation link, finding a consistent positive trend across multiple methods. • By focusing on Felty Syndrome-a condition linked to high-titer rheumatoid factor-we address prior RA study heterogeneity and offer a more precise causal model. • The results highlight the need to assess AF risk specifically in seropositive rheumatoid arthritis subgroups in future research.