Background: Interstitial lung disease (ILD) associated with clinically amyopathic dermatomyositis (CADM) is a potentially fatal condition in which the clinical features are not well understood. The aim of the present study was to clarify the differences in clinical characteristics and prognosis of patients with ILD associated with CADM (CADM-ILD) and classic dermatomyositis associated with ILD (DM-ILD).
Methods: We retrospectively studied consecutive patients with CADM-ILD and classic DM-ILD who were hospitalized between 2001 and 2007 at Nagasaki University Hospital. The study group consisted of 11 patients with CADM-ILD and 16 patients with classic DM-ILD. We compared the clinical features and prognosis between the two forms.
Results: The Pao(2)/Fio(2) ratio was significantly lower in patients with CADM-ILD than in patients with classic DM-ILD. The lymphocyte subsets ratio in the BAL fluid of patients with CADM-ILD was significantly higher than the corresponding ratio in patients with classic DM-ILD. ILD is classified as acute or chronic, and the acute subtype was more common in patients with CADM-ILD than in those with classic DM-ILD. The mortality rate for patients with CADM-ILD (45%) was much higher than that for patients with classic DM-ILD (6%), and all of the CADM deaths occurred in the group of patients with acute CADM-ILD.
Conclusion: Our data suggest that the higher prevalence of the acute subtype of ILD in patients with CADM results in a higher mortality rate for patients with CADM-ILD.