BACKGROUND Given the phenotypic similarities between rheumatoid arthritis (RA)–associated interstitial lung disease (ILD) (hereafter, RA-ILD) and idiopathic pulmonary fibrosis, we hypothesized that the strongest risk factor for the development of idiopathic pulmonary fibrosis, the gain-of-function MUC5B promoter variant rs35705950, would also contribute to the risk of ILD among patients with RA. METHODS Using a discovery population and multiple validation populations, we tested the association of the MUC5B promoter variant rs35705950 in 620 patients with RA-ILD, 614 patients with RA without ILD, and 5448 unaffected controls. RESULTS Analysis of the discovery population revealed an association of the minor allele of the MUC5B promoter variant with RA-ILD when patients with RA-ILD were compared with unaffected controls (adjusted odds ratio, 3.8; 95% confidence interval [CI], 2.8 to 5.2; P = 9.7×10−17). The MUC5B promoter variant was also significantly overrepresented among patients with RA-ILD, as compared with unaffected controls, in an analysis of the multi-ethnic case series (adjusted odds ratio, 5.5; 95% CI, 4.2 to 7.3; P = 4.7×10−35) and in a combined analysis of the discovery population and the multiethnic case series (adjusted odds ratio, 4.7; 95% CI, 3.9 to 5.8; P = 1.3×10−49). In addition, the MUC5B promoter variant was associated with an increased risk of ILD among patients with RA (adjusted odds ratio in combined analysis, 3.1; 95% CI, 1.8 to 5.4; P = 7.4×10−5), particularly among those with evidence of usual interstitial pneumonia on high-resolution computed tomography (adjusted odds ratio in combined analysis, 6.1; 95% CI, 2.9 to 13.1; P = 2.5×10−6). However, no significant association with the MUC5B promoter variant was observed for the diagnosis of RA alone. CONCLUSIONS We found that the MUC5B promoter variant was associated with RA-ILD and more specifically associated with evidence of usual interstitial pneumonia on imaging. (Funded by Société Française de Rhumatologie and others.)

Question addressed by the studyMethotrexate (MTX) is a key anchor drug for rheumatoid arthritis (RA) management. Fibrotic interstitial lung disease (ILD) is a common complication of RA. Whether MTX exposure increases the risk of ILD in patients with RA is disputed. We aimed to evaluate the association of prior MTX use with development of RA-ILD.MethodsThrough a case-control study design with discovery and international replication samples, we examined the association of MTX exposure with ILD in 410 patients with chronic fibrotic ILD associated with RA (RA-ILD) and 673 patients with RA without ILD. Estimates were pooled over the different samples using meta-analysis techniques.ResultsAnalysis of the discovery sample revealed an inverse relationship between MTX exposure and RA-ILD (adjusted odds ratio [OR], 0.46; 95% confidence interval [CI], 0.24–0.90; p=0.022), which was confirmed in the replication samples (pooled adjusted OR, 0.39; 95% CI, 0.19–0.79; p=0.009). The combined estimate using both the derivation and validation samples revealed an adjusted OR of 0.43 (95% CI, 0.26–0.69; p=0.0006). MTX ever users were less frequent among patients with RA-ILD compared to those without ILD, irrespective of chest high resolution computed tomography pattern. In patients with RA-ILD, ILD detection was significantly delayed in MTX ever users compared to never users (11.4±10.4 years and 4.0±7.4 years, respectively; p<0.001).Answer to the QuestionOur results suggest that MTX use is not associated with an increased risk of RA-ILD in patients with RA, and that ILD was detected later in MTX treated patients.

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Objective.To describe the evolution of the pulmonary function in patients with interstitial lung disease (ILD) who are positive for at least 1 of the antisynthetase antibodies (ASAB) after medical treatment, and to compare whether the evolution of pulmonary function is associated with the type of ASAB.Methods.Patients with ILD and positive for at least 1 of the ASAB (anti-Jo1, anti-PL7, anti-PL12, anti-EJ, or anti-OJ) were included. The clinical evolution, time until death or censoring, and improvement of lung disease were registered.Results.The study included 118 patients. Most of the patients had a high extent of ground glass opacities in high-resolution computed tomography (HRCT) and low extent of fibrosis. In the final evaluation of pulmonary function (median 749.5 days of followup), 67% of the patients had lung disease improvement. The improvement occurred within the first 6 months after initiating medical treatment; thereafter, pulmonary function remained stable in most of the patients. A decrease of the extent of ground glass opacities was demonstrated in HRCT at followup in those patients with pulmonary improvement. No differences were observed in the percentage of patients who achieved improvement between the ASAB groups, or in survival.Conclusion.Improvement of pulmonary function was observed in 67% of the patients. Improvement was observed in all ASAB groups and occurred within 6 months after initiating medical treatment.