Dermatomyositis (DM) is an autoimmune disease characterized by skeletal muscle weakness, skin rashes, and the presence of autoantibodies in the blood. These autoantibodies help clinicians diagnose and treat patients by defining unique patient subsets with different clinical symptoms and treatment responses. This study by researchers at Johns Hopkins and the NIH sought to define the clinical features of patients with Mi2 antibodies and investigate how these features evolve over time. Patients with anti-Mi2 positive DM had more severe muscle disease, characterized by muscle weakness and increased creatine kinase (CK) levels, which is a marker of muscle damage. Nearly all dermatomyositis patients with Mi2 autoantibodies experienced muscle weakness throughout the duration of their follow-up. However, most patients with anti-Mi2 antibodies had improved strength and CK levels after treatment.
Why was this study done?
Myositis-specific autoantibodies (MSAs) are protein markers in the blood that physicians use to help diagnose and treat patients with different types of muscle diseases, such as dermatomyositis. Understanding the clinical signs and symptoms associated with each antibody can be helpful in disease monitoring and prognosis. The study team therefore sought to characterize the clinical features associated with anti-Mi2 antibodies in DM over time.
How was this study done?
Researchers studied a total of 58 patients with Mi2-positive DM from the Johns Hopkins Myositis Cohort. In addition, patients with other types of myositis were included for comparison — 143 patients with Mi2-negative DM, 162 patients with anti-synthetase syndrome, and 170 patients with immune-mediated necrotizing myopathy. Each patient’s chart was reviewed for symptoms they experienced over time, and their disease characteristics (muscle biopsy characteristics, CK levels, etc.) were compared to those of other myositis types.
What were the major findings?
The majority of DM patients with Mi2 antibodies experienced weakness over their disease course but improved with treatment. Compared to patients with other types of DM, those with Mi2 antibodies were found to have higher CK levels and more muscle weakness, indicating more severe muscle disease. Among 10 patients with multiple blood samples collected over 4 or more years, the level of Mi2 autoantibodies decreased in all patients and normalized in three – two of whom stopped immunosuppressant treatment and never relapsed. Further, despite their more severe muscle involvement, patients with Mi2-positive DM had less calcinosis (i.e., accumulation of calcium deposits under the skin), interstitial lung disease, and fever than patients with Mi2-negative DM.
What is the impact of this work?
This study improves our understanding of myositis patients with Mi2 autoantibodies, which may assist clinicians in diagnosing and treating this subset of patients. The study team observed important clinical features that are associated with Mi2 antibodies, confirming their clinical value and their importance in disease diagnosis, monitoring, and prognosis.
This research was supported by:
- The Jerome L. Greene Foundation
More prominent muscle involvement in patients with dermatomyositis with anti-Mi2 autoantibodies. Pinal-Fernandez I, Mecoli CA, Casal-Dominguez M, Pak K, Hosono Y, Huapaya J, Huang W, Albayda J, Tiniakou E, Paik JJ, Johnson C, Danoff SK, Corse AM, Christopher-Stine L, Mammen AL. Neurology Nov 2019, 93 (19) e1768-e1777.