Interstitial lung disease in polymyositis and dermatomyositis: clinical course and response to treatment

To assess the prevalence, clinical characteristics, and treatment options of patients with interstitial lung disease (ILD) in polymyositis and dermatomyositis (PM/DM).

Sixty-three consecutive patients with PM/DM underwent standardized screening. Patients with ILD were monitored prospectively, and graded immunosuppression was administered according to the rate of clinical progression.

ILD was diagnosed in 20 of 63 patients (32%). Generally, the clinical and serologic findings of the anti-Jo1 syndrome were present. Follow-up evaluation disclosed either a progressive or a nonprogressive course. The 10 patients with progressive ILD were distinguished from the nonprogressive group by extensive ground-glass opacities on high-resolution computed tomography (HRCT) and by bronchoalveolar lavage (BAL) neutrophilia. Intravenous pulse cyclophosphamide prevented further progression in all 10 patients and led to some functional improvement. In the 10 patients without rapidly progressive lung disease, immunosuppression of moderate intensity stabilized pulmonary findings during a median 35 months of follow-up.

The prevalence of ILD in our patients with PM/DM was 32%; this emphasizes the need for pulmonary screening in all PM/DM patients. Progressive disease, featuring ground-glass opacities on HRCT and an inflammatory BAL cell profile, is amenable to intensive immunosuppression. Conversely, patients who do not have these HRCT and BAL features appear to have a low risk of pulmonary deterioration.

Because the treatment for ILD seems to depend on the rate of clinical progression, future therapeutic trials of lung disease in PM/DM should stratify patients accordingly.