Which RA patients should be given methotrexate?
The available evidence suggests that ILD is a risk factor for MTX pneumonitis. MTX has been reported to improve ILD due to RA  and is also used to treat inflammatory muscle disease with anti-synthetase antibodies, a condition associated with ILD . However, the benefit of MTX in ILD has not been substantiated in a randomized trial. Patients with RA are unwilling to risk life-threatening toxicity due to DMARDs . In our literature review, 48% of patients who had MTX pneumonitis had pre-existing lung disease (Table 1). We suggest avoiding MTX in patients with established ILD. Gas transfer is invariably reduced (TLCO <70% predicted) in such patients. If all RA patients with TLCO <70% are investigated for ILD by HRCT, we estimate that at least 5% of those considered for MTX may need to be treated with an alternative DMARD . A more compelling reason to avoid MTX in these patients is that they may have poor lung reserve and hence are at risk of respiratory failure in the event