Clinical manifestation and prognostic factor in anti-melanoma differentiation-associated gene 5 antibody-associated interstitial lung disease as a complication of dermatomyositis.

OBJECTIVE The aim of this study is to evaluate the clinical manifestation and prognostic factors of anti-melanoma differentiation-associated gene 5 (MDA5) antibody-associated interstitial lung disease (ILD) with DM. METHODS Fourteen patients who presented with anti-MDA5 antibody and 10 patients with anti-aminoacyl-tRNA synthetase (ARS) antibody were enrolled. All patients were diagnosed as having DM with ILD. Clinical manifestations in the patients with anti-MDA5 antibody were compared with those in the patients with anti-ARS antibody. RESULTS The frequencies of acute/subacute interstitial pneumonia (A/SIP) and fatal outcome were significantly higher in the subset with anti-MDA5 antibody. The creatine kinase (CK) value was significantly lower and the gamma-glutamyl transpeptidase and ferritin values were significantly higher in the subset with anti-MDA5 antibody. Significant correlations were found between PaO(2)/F(i)O(2) and ferritin (r(s) = -0.59, P = 0.035), alveolar-arterial oxygen difference (A-aDO(2)) and KL-6 (r(s) = 0.73, P = 0.016) and A-aDO(2) and ferritin (r(s) = 0.66, P = 0.013) in the subset with anti-MDA5 antibody. The most significant prognostic factor was ferritin. The cumulative survival rate was significantly lower (P < 0.0001) in the subset with ferritin >or=1600 ng/ml than that in the subset with ferritin <1600 ng/ml in anti-MDA5 antibody-associated ILD. CONCLUSION Both serum ferritin and anti-MDA5 antibody are powerful indicators for the early diagnosis of A/SIP with DM. Ferritin also predicts disease severity and prognosis for patients with anti-MDA5 antibody. Intensive treatment should be administered to cases that have anti-MDA5 antibody-associated ILD with DM showing hyperferritinaemia, especially if the ferritin level is >or=1600 ng/ml.