Interstitial lung disease related to dermatomyositis. Comparative study with patients without lung involvement

To compare clinical and histopathological data and outcome of patients with dermatomyositis (DM) with and without interstitial lung disease (ILD).

Patients diagnosed with definite DM were prospectively evaluated. Clinical and analytical data were recorded and muscle biopsies were performed. In patients with respiratory symptoms an extensive pulmonary evaluation was done.

104 patients were diagnosed with idiopathic inflammatory myopathy, 63 with DM. Eight of the patients with DM (13%) also had associated ILD. Arthralgia and fever were more frequently seen in the ILD group and there was no associated malignant condition. Either atypical or nonspecific cutaneous lesions were more frequently seen in ILD patients. Anti Jo-1 antibodies were positive in 75% of the patients with ILD and in 3% of patients with DM without ILD (p < 0.001). Bronchoalveolar lavage measured for cell count showed an increased lymphocyte count in 3/5 cases in which this data was recorded. Lung biopsies showed interstitial pneumonitis in 2 cases and desquamative interstitial pneumonitis in one. All patients achieved complete remission of muscular involvement. With respect to lung disease, 4/8 obtained complete remission, and the other 4 showed partial improvement. No significant statistical differences in terms of survival were found between the 2 groups.

ILD associated with DM represents a subgroup of DM with clinical and biological differences. However, such patients do not have poorer prognosis than patients without ILD if they are managed aggressively with immunosuppressive drugs.