Assessing the promoter variant in a large cohort of systemic sclerosis-associated interstitial lung disease.

Objective: The common gain-of-function variant rs35705950, located in the promoter of gene, has been strongly associated with interstitial lung diseases (ILDs) of different aetiology, such as idiopathic pulmonary fibrosis (IPF) and rheumatoid arthritis-associated ILD (RA-ILD). In this study, we aimed to investigate the association of this variant and its nearby single nucleotide polymorphisms (SNPs) in the largest cohort of systemic sclerosis-associated ILD (SSc-ILD) to date.

Methods: Samples were collected from blood/saliva, followed by DNA extraction and genotyping using SNP arrays. Data for rs35705950 and additional 903 variants within 100 Kb were obtained using genomic imputation. Subsequently, we tested their association in a meta-analysis to increase the consistency of the results, including 10 European ancestry cohorts comprising 2363 patients with SSc-ILD, 3526 SSc patients without ILD and 15 076 controls.

Results: Meta-analysis showed no significant association between rs35705950 and SSc-ILD, either comparing patients with SSc with and without ILD (p value: 0.588, OR: 1.05, 95% CI: 0.87 to 1.27) nor patients with SSc-ILD with controls (p value: 0.061, OR: 1.16, 95% CI: 0.99 to 1.36). Moreover, none of the additional 903 variants tested in the genomic region reached statistical significance.

Conclusion: Despite analysing the largest and most statistically powered SSc-ILD cohort to date, we found no evidence of association between the promoter variant rs35705950 and its surrounding SNPs with SSc-ILD. These results suggest that the pathogenic mechanisms underlying SSc-ILD may only partially overlap with those of other similar ILDs, such as IPF or RA-ILD. This highlights the need for further studies regarding their genetic architecture.