THU0521 JUVENILE DERMATOMYOSITIS IN GERMANY – DATA OF THE NATIONAL PEDIATRIC RHEUMATOLOGY DATABASE WITH SPECIAL REGARD TO MYOSITIS-SPECIFIC ANTIBODIES AND ASSOCIATED CLINICAL PHENOTYPES
Authors: Claudia Sengler, Svea Horn, Nadine Grösch, Jens Klotsche, Martina Niewerth, Fabian Speth, Peter Haas, Claas Hinze, Gerd Horneff, Tilmann Kallinich, Frank Weller-Heinemann, Nadine Unterwalder, Kirsten Minden
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Next to weakness of the proximal muscles and typical skin lesions as leading symptoms in juvenile dermatomyositis (JDM) there can be involvement of other organ systems and tissues. Myositis-specific antibodies (MSA) may help to distinguish clinically distinct phenotypes <h3>Objectives</h3> 1) to analyse the clinical presentation of JDM and how diagnosis was verified and 2) to determine the spectrum of MSA and the associated clinical phenotypes in a German cohort of JDM patients. <h3>Methods</h3> We analyzed data of the national pediatric rheumatology database (NPRD), where children and adolescents with chronic rheumatic diseases are documented yearly by means of disease-specific questionnaires. Cross-sectional data of patients with JDM documented between 2014 and 2016 were analyzed. MSA were determined by a commercial multiplex array. To further specify the phenotype and patient's outcome, an additional retrospective chart review was conducted. <h3>Results</h3> We identified 186 patients with a diagnosis of JDM (69% female). Mean age at disease onset was 6.8 ± 3.5 years, mean time between first symptoms and first contact to a pediatric rheumatologist was 6.1 ± 8.9 months, mean age at documentation was 11.5 ± 4.4 years. The following diagnostic procedures were pathologic/positive for JDM: Histology 44/147 (30%), electromyography 28/144 (19%), magnetic resonance imaging 103/148 (70%), Creatine kinase (CK) elevation at diagnosis 126/148 patients (85%). At last consultation (mean disease duration 5.0 ± 3.9 years), the mean physician's global assessment of disease activity (PGA, NRS 0 – 10) was 1.6 ± SD 2.3, the mean manual muscle test (MMT, range 0 – 80, best 80) was 69.7 ± SD 19, the mean disease activity score (DAS, range 0 – 20, best 0) was 4.4 ± D 4.7, the mean CHAQ was 0.5 ± SD 0.8. MSA testing was performed on 88 patients (73% female); 42% tested positive: anti-NXP2 16%, anti-TIF1γ 14%, anti-MDA5 6%, anti-Mi2 3%, anti-synthetase-antibodies 3%. The most common clinical feature was dysphagia in patients with anti-NXP2, calcinosis in patients with anti-TIF1γ, lung involvement in patients with anti-synthetase antibodies, and pronounced muscle weakness in patients with anti-Mi2. Patients with anti-MDA5 were characterized by frequent lung involvement, mucosal ulcers, fever and polyarticular arthritis of small joints. Muscle weakness tested by Childhood Myositis Assessment Score (CMAS) was significantly associated with an increased CK level. At last consultation, 32% and 14% received oral glucocorticoids (GC) &lt; 0.2 mg/kg or ≥ 0.2 mg/kg body weight, respectively, 52% were treated with methotrexate (MTX) and 27% with intravenous immunoglobulins (last 12 months). PGA was ≤ 1 in 65% of patients at last consultation, 22% of those were off therapy. <h3>Conclusion</h3> Demographic and clinical parameters of patients with JDM in Germany are comparable to JDM-cohorts in other countries. MRI has gained diagnostic importance and is used more than twice as often as biopsy. MSA could be found in almost half of the patients. Clinical phenotypes were associated with specific MSA. After 5 years, 2/3 of patients had an inactive disease, but about half of all patients still received MTX and GC therapy. <h3>Disclosure of Interests</h3> Claudia Sengler: None declared, Svea Horn: None declared, Nadine Grösch: None declared, Jens Klotsche: None declared, Martina Niewerth: None declared, Fabian Speth: None declared, Peter Haas Grant/research support from: Pfizer, Claas Hinze: None declared, Gerd Horneff: None declared, Tilmann Kallinich Grant/research support from: Novartis, Speakers bureau: Sobi, Roche, Novartis, CLB, Frank Weller-Heinemann: None declared, Nadine Unterwalder: None declared, Kirsten Minden Consultant for: AbbVie