Clinical and immunological characteristics and prognosis of patients with autoantibody negative dermatomyositis: a case control study

Objectives: Myositis-specific antibodies (MSAs) and myositis-associated antibodies (MAAs) are associated with distinctive dermatomyositis (DM) clinical phenotypes. The aim of this study is to explicate the clinical and immunological features of MSAs-negative DM patients. Methods: A total of 515 individuals diagnosed with DM was screened from 2013 to 2022 and 220 DM patients were enrolled in this retrospective cohort. Clinical and laboratory data of these patients were analyzed. Results: MSAs-negative DM patients were categorized into two groups: MAAs-negative (MSAs (−)/MAAs (−)) group and MAAs-positive (MSAs (−)/MAAs (+)) group. The percentage of Raynaud’s phenomenon (P=0.026) was higher in the MSAs (−)/MAAs (+) DM patients than the MSAs-positive DM patients and MSAs (−)/MAAs (−) DM patients. The proportion of rapidly progressive interstitial lung disease (RP-ILD) in the MSAs-negative DM patients was lower than that in the MSAs-positive group. The MSAs (−)/MAAs (+) group had a higher proportion of organizing pneumonia and usual interstitial pneumonia (P=0.011), and elevated eosinophils in their bronchoalveolar lavage fluid (P=0.008). Counts of lymphocytes (P=0.001) and CD16CD56 natural killer (NK) cells (P=0.012) were higher in the MSAs-negative group. Additionally, the percentage of CD4TNFα (P=0.040), CD4IFNγ (P=0.037), and CD4IL-2 (P=0.018) cells among total CD4 T cells were higher in the MSA-negative DM patients compared with the MSAs-positive DM patients. Besides, MSAs-negative patients demonstrated a more favorable prognosis than MSAs-positive patients. Multivariable regression analysis identified advanced onset age, higher level of carcinoembryonic antigen (CEA), and RP-ILD as risk factors for mortality in DM patients. Conclusions: Compared with MSAs-positive group, MSAs-negative DM patients suffered less from organ involvement compared with MSAs-positive group and tend to have better prognosis. (Table presented.).