Interstitial pulmonary fibrosis occurs in approximately 9% of patients with PM/DM, yet its effect on the course of PM/DM has been scarcely noted. In this report, two patients with PM/DM and IPF were presented to highlight the fact that pulmonary disease can overshadow the primary muscle disorder and progress despite therapy with corticosteroids and nonsteroidal immunosuppression. Our patients were added to previously reported cases and an overview of PM/DM and IPF was presented. Sixty-seven patients with the diagnosis of PM/DM and IPF, with a mean age of 60 +/- 18 years, were identified. Pulmonary complaints were present in 64 cases. Fever was present in 18, arthritis or arthralgias in 11, and Raynaud's phenomenon in 9. Forty percent died after followup of 31 +/- 32 months. This mortality was significantly higher (P less than .05) than that in 745 historical controls with PM/DM without IPF. Progressive IPF was the immediate cause of death in 58% of those who died. A subgroup of 29 patients who had histologic documentation of both myositis and IPF had a mortality of 62% after 22 +/- 25 months. In this latter group, six patients had RP; five of these died. Patients who were not treated with corticosteroids also appeared to fare worse but, given the small number of patients involved, definite conclusions cannot be drawn. We conclude that patients with PM/DM can be adversely affected by the presence of IPF and that this negative impact may be exaggerated by RP and perhaps by lack of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)