Chronological evaluation of the onset of histologically confirmed interstitial pneumonia associated with polymyositis/dermatomyositis

Objective The present study was designed to determine the chronological sequence of interstitial pneumonia, skin involvement, and muscle involvement associated with polymyositis/dermatomyositis (PM/DM). Methods We examined our own cases of histologically confirmed interstitial pneumonia associated with PM/DM. In addition, a review of the literature was done to evaluate other cases of histologically confirmed interstitial pneumonia associated with PM/DM. Lung involvement was the first clinical symptom for all of our 8 patients. Results Including the literature review and our 8 cases, there were 94 patients with PM/DM in whom interstitial pneumonia was histologically confirmed (36 PM, 50 DM, and 8 amyopathic DM). Chronological evaluation between the diagnosis of PM/DM and lung involvement demonstrated that most lung involvement occurred just before or just after the diagnosis of PM/DM. Interstitial pneumonia was preceded in 35 of 87 evaluable patients [21 cases with PM (61.8 %), 14 cases with DM and amyopathic DM (40.2%)]. In 60 of 87 evaluable patients (69.0%), lung involvement occurred as a clinical manifestation at the diagnosis of PM/DM. Conclusion The present data demonstrate that interstitial pneumonia was frequently the initial onset in patients with PM/DM.