Myositis-specific autoantibodies and their associated phenotypes in juvenile dermatomyositis: data from a German cohort

Objective To describe a German cohort of patients with juvenile dermatomyositis (JDM) and to evaluate clinical manifestations, disease course and prognosis in JDM patients with a certain myositis-specific autoantibody. Methods Cross-sectional data on patients with JDM documented in the National Paediatric Rheumatologic Database in Germany between 2014 and 2016 were analysed. In a subgroup of the cohort, MSAs were determined with a commercial multiplex array, and a retrospective chart review was conducted to specify the clinical phenotype and patient outcome. Results The total cohort consisted of 196 patients with JDM (mean age 12.2 +/- 4.0 years, mean disease duration 5.1 +/- 3.8 years, 70% female). Apart from typical skin changes and muscle weakness, 41% of patients also had arthritis and/or contractures, 27% had calcinosis and approximately 10% had interstitial lung disease. Immunoblot testing was performed on the sera of 91 (46%) patients, detecting MSAs in 44% of patients. Patient groups with specific MSAs differed in clinical characteristics such as calcinosis, dysphagia, and lung and joint involvement. The extent of muscle weakness evaluated by the Childhood Myositis Assessment Scale was significantly associated with an increased level of creatine kinase. Patients with anti-MDA5 were particularly affected by polyarthritis of the small joints. After 5 years, 51patients of the MSA cohort (56.0%) achieved an inactive disease state, 12/51 (23.5%) were off therapy. Conclusion Patients with JDM in Germany show a broad spectrum of clinical manifestations that can be grouped into homogeneous groups using MSA, which also helps to predict the course and prognosis of the disease.

Automated summary

The study aimed to describe a cohort of German patients with juvenile dermatomyositis (JDM) and evaluate their clinical manifestations and prognosis based on a specific myositis-specific autoantibody (MSA). The results showed that JDM patients in Germany exhibited a wide range of clinical manifestations, which could be grouped using MSAs, and this classification helped to predict disease course and prognosis.