Evaluation of disease course and major complications in juvenile idiopathic inflammatory myopathy patients

Objective: Idiopathic inflammatory myopathies (IIM) are chronic, multisystemic, autoimmune diseases affecting mainly the skin and proximal muscles. In this study, we aimed to determine the factors that may predict the disease course and to investigate the effect of major complications on the disease course in juvenile IIM patients. Methods: This retrospective, observational study was conducted in Ankara Pediatrics Hematology Oncology Training and Research Hospital between 2009 and 2019 and University of Health Sciences Turkiye, Ankara Bilkent City Hospital between 2019 and 2022 with patients who were followed up for at least 6 months with a diagnosis of IIM. Demographic, clinical, laboratory findings, myositis-specific antibodies, treatments, disease course and complications were recorded. Results: Thirty patients with IIM were included in the study. Eighteen (60%) of the patients were female. The median age at diagnosis was 118.5 [inter quartile range (IQR): 76.5-139.5] months. Twenty-six (86.7%) patients had muscle weakness, 27 (90.0%) had skin manifestations, 11 (36.7%) had arthritis, 4 (13.3%) had gastrointestinal system involvement, 2 (6.6%) had generalized edema, 1 (3.3%) had pulmonary involvement, and 1 (3.3%) had cardiac involvement. The median follow-up period was 25 (IQR: 17.7-72.5) months. Monocyclic course was observed in 15 (50.0%), polycyclic in 4 (13.3%) and persistent in 11 (36.6%) patients. Calcinosis developed in 4 (13.3%) patients and severe steroid side effects in 3 (10%) patients. The 6th month Childhood Myositis Assessment Scale (CMAS) score was significantly correlated with monocyclic disease course. Conclusion: CMAS score is useful tool in predicting the disease course in patients with IIM. Patients with low 6th month CMAS score should be carefully followed up considering the increased possibility of polycyclic/persistent course.