ILD in RA and PsA Save

Interstitial lung disease (ILD) is a severe extra articular manifestation of RA, with limited treatment strategies and poor prognosis. While for a long time RA treatments, such as methotrexate (MTX), have been considered a risk factor, recent data have shown the innocuity of MTX on lung disease (and in fact suggests it could reduce risk of ILD by increasing disease control and remission). However, some inconsistent data have been proposed on the effect of bio/tsDMARDs on the risk of ILD.

In this Scandinavian study, Provan et al. (OP0006) have identified incident ILD cases in patients with PsA or RA starting a bio/tsDMARD amongst Denmark, Finland, Iceland, Norway and Sweden registries through hospital and death database linkage. 

Out of 37000+ patients with RA, 12000+ patients with PsA and 560000+ population subjects, 300, 30 and 400 ILD cases were observed during follow-up, respectively. Among RA and PsA patients initiating bio/tsDMARDs, the risk of ILD was higher than in the general population, and the risk of ILD in RA (HR=10) was approximately twice that of PsA patients (HR=5). Amongst patients with RA a significantly increased HR was noted for rituximab 1.7 when compared to Etanercept. MTX co-medication was used in roughly half of RA/PsA patients but did not give an increased risk of ILD compared to no use of MTX-comedication.

This large-scale register study highlights a few interesting concepts, although inevitable biases are to be noticed, especially in the absence of adjustment for smoking status or comorbidities. 

The first concept is the increased risk of ILD in PsA -although to a twice lesser extent than in RA- which has been described recently in other reports and is yet not well understood. In this study, the possibility that this association is indirect and driven by smoking status and/or comorbidities should not be overlooked. The second interesting concept is the use of Rituximab associated with a higher risk of developing ILD in RA, which might represent a confounding by indication, representing patients with a more severe or established disease. Finally, some reassuring data, confirming previous findings, showing that use of MTX and/or bio/tsDMARDs were not associated with an increased risk of ILD in both RA and PsA.