Azathioprine in connective tissue disease-associated interstitial lung disease : data from a retrospective single centre study
Background: Immunosuppressive agents and corticosteroids are the standard treatments for patients with connective tissue disease associated ILD (CTD-ILD). This retrospective study aimed to provide data on tolerability and efficacy of azathioprine in CTD-ILDs. Methods: 56 CTD-ILD patients treated with azathioprine between 2003 and 2014 were included in the study. Azathioprine was added to oral corticosteroids as a corticosteroid sparing agent. Patients were assessed every 3 months in the outpatient clinic. Results: 15 patients (27%) discontinued treatment due to side effects, mostly due to elevated liver enzymes, within the first 3 months. The mean treatment duration was 34 months with a range of 3 to 105 months. 41 patients were treated for longer than 3 months, and 27 of those (66%) had stable or improved pulmonary function during treatment. In patients who remained stable or improved, the mean FVC was 62 ± 17 % pred at the initiation of treatment and 65 ± 17 % pred at the last follow up visit (p=0.036), and the mean DLCO was 38 ± 16 % pred at initiation of treatment and 39 ± 17% pred at the last follow up visit (p=0.06). The mean serum level of Krebs von den Lungen-6 (KL-6) was elevated in all patients, it was 1655±821 U/mL at start of treatment and 1589±744 U/mL at the last follow up visit. Serum KL-6 levels showed a decline in stable or improved patients during treatment, but this was not significant (p= 0.210). Conclusions: Our findings confirm the role of azathioprine in treatment of CTD-ILD. While early drug intolerance is frequent, most patients who tolerated the drug well achieved long-term stabilisation or improvement of lung function. Randomised controlled trials are still needed to validate these results. KL-6 seems to be a promising biomarker for monitoring CTD-ILDs under treatment.