The case of methotrexate and the lung: Dr Jekyll and Mr Hyde

Involvement of the respiratory system, the commonest extra-articular manifestation of rheumatoid arthritis (RA), occurs to some extent in a large proportion of patients with RA. Any of the pulmonary compartments can be affected, either secondary to RA itself, or in relation to drug toxicity or opportunistic infection [1]. RA-associated interstitial lung disease (RA-ILD) is an increasingly recognised complication of RA, in many ways similar to idiopathic pulmonary fibrosis [2]. Clinically relevant RA-ILD may be present in up to 10% of patients with RA, and is associated with significant morbidity and mortality [1, 3], with no optimal treatment determined. Methotrexate can induce subacute hypersensitivity pneumonitis, a potentially lethal condition that should lead to drug discontinuation; however, its use does not seem to be associated with increased risk of chronic fibrosing ILD in rheumatoid arthritis https://bit.ly/3sCyjji