Analysis of dermatomyositis-specific autoantibodies and clinical characteristics in Japanese patients

Dermatomyositis (DM) is an idiopathic systemic inflammatory disease that is often accompanied by interstitial lung disease (ILD) or internal malignancy. New autoantibodies, anti-clinically amyopathic dermatomyositis 140 (anti-CADM-140) antibody (Ab) and anti-155/140 Ab, as well as anti-aminoacyl-tRNA synthetase (anti-ARS) Ab and anti-Mi-2 Ab, have been discovered and their utility indicated. However, the association between these autoantibodies and the clinical characteristics of DM is not fully understood, and it is unclear whether anti-155/140 Ab is specific to DM patients with internal malignancy. Therefore, we analyzed 55 DM patients and 18 non-DM patients with malignancy to evaluate the clinical characteristics, especially skin manifestations, in association with DM-specific autoantibodies detected by immunoprecipitation. Six patients (11%) had anti-CADM-140 Ab, nine (16%) had anti-155/140 Ab, eight (15%) had anti-ARS Ab and six (11%) had anti-Mi-2 Ab. The frequency of DM patients positive for any type of autoantibody was 53%. Among the 20 DM patients with ILD, three (15%) had both anti-CADM-140 Ab and rapidly progressive ILD, and required intensive therapy (P < 0.05). ILD found in anti-ARS Ab-positive patients did not progress rapidly. The prevalence of muscle involvement in patients with anti-CADM-140 Ab was 83%. Among the 18 DM patients with internal malignancy, four (22%) had anti-155/140 Ab, and internal malignancy was found in four cases (44%) of nine anti-155/140 Ab-positive patients. None of the non-DM patients with malignancy were positive for anti-155/140 Ab. In conclusion, the results of the present study indicate that anti-155/140 Ab is specific to DM patients with internal malignancy and that we may be able to predict prognosis of ILD and the presence of malignancy to some extent, suggesting that examination of autoantibodies in DM patients is clinically very useful. However, further investigation is needed because several findings differ from those of previous reports.