Predicting factors of interstitial lung disease in dermatomyositis and polymyositis.

The aim of this study was to define the predicting factors and evaluate the prognosis of interstitial lung disease in dermatomyositis/polymyositis. For the period 1995-2005, we retrospectively reviewed the clinical information and laboratory data of 56 patients who were diagnosed as definite and probable dermatomyositis and polymyositis. Interstitial lung disease is common (41.9%) in these patients. Dyspnoea and cough were the two most common initial presentations. Anti-Jo1 antibody was more common in those with interstitial lung disease. Univariate and multivariate analyses identified primary idiopathic dermatomyositis subtype, cough and dyspnoea at onset to be the three independent clinical predicting factors of interstitial lung disease. High serum lactate dehydrogenase level (>400 U/l) was inversely associated with development of interstitial lung disease (OR 0.088, p=0.031). Serum lactate dehydrogenase level and presence of anti-Jo1 antibody can serve as laboratory indicators of lung complications. Patients with malignancy and older age at onset (more than 60 years) had poorer prognosis for dermatomyositis/polymyositis (p=0.047 and p=0.035, respectively). Interstitial lung disease did not affect the survival of dermatomyositis/polymyositis patients.