Interstitial lung disease in classic and skin-predominant dermatomyositis: a retrospective study with screening recommendations.

OBJECTIVES (1) To determine the prevalence of interstitial lung disease (ILD) and isolated low diffusing capacity for carbon monoxide (DLCO) in a large cohort of outpatients with dermatomyositis. (2) To compare the pulmonary abnormalities of patients with classic dermatomyositis and those with skin-predominant dermatomyositis. DESIGN Retrospective cohort study. SETTING University hospital outpatient dermatology referral center. Patients Medical records of 91 outpatients with adult-onset dermatomyositis seen between May 26, 2006, and May 25, 2009, were reviewed. MAIN OUTCOME MEASURES Presence of ILD on thin-slice chest computed tomographic (CT) scans and DLCO. RESULTS Of the 71 patients with dermatomyositis who had CT or DLCO data, 16 (23%; 95% confidence interval [CI], 13%-33%) had ILD as defined by CT results [corrected]. All patients with ILD had a reduced DLCO, and the ILD prevalence was not different between patients with skin-predominant dermatomyositis (10 of 35 [29% ]) and those with classic dermatomyositis (6 of 36 [17% ]) (P = .27). Eighteen of 71 patients with dermatomyositis (25%; 95% CI, 15%-36%) (7 of 35 [20%] with skin-predominant dermatomyositis; 11 of 36 [31%] with classic dermatomyositis; P = .41) had a low DLCO in the absence of CT findings showing ILD. The prevalence of malignant disease was higher in patients with classic dermatomyositis than in those with skin-predominant dermatomyositis (P = .02), and no patients with skin-predominant dermatomyositis had internal malignant disease. CONCLUSIONS Radiologic ILD and isolated DLCO reductions, which may signify early ILD or pulmonary hypertension, are common in dermatology outpatients with both classic and skin-predominant dermatomyositis. Because DLCO testing is both inexpensive and sensitive for pulmonary disease, it may be appropriate to screen all patients with dermatomyositis with serial DLCO measurements and base further testing on DLCO results.