AB0697C THE ASSOCIATION OF ANTI-MELANOMA DIFFERENTIATION-ASSOCIATED PROTEIN 5 AND SEASONAL PATTERNS IN ONSET OF IDIOPATHIC INFLAMMATORY MYOPATHIES IN KOREA

Background: There was some reports of seasonal association with myopsitis onset. With the discovery of new myositis-specific autoantibodies (MSA), detailed grouping of idiopathic inflammatory myopathies was possible. Therefore, we evaluated the seasonal patterns in the onset of idiopathic inflammatory myositis (IIM) with MSA in Korea. Objectives: To evaluate the correlation between MSA and seasonal patterns of IIM in Korea. Methods: A total of 90 patients who met the criteria for probable or definite PM or DM and for whom data were collected from 7 referal centers in korea. 16 myositis-specific autoantibodies were detected by immunoblot with patient’s serum. Statistical analyses were performed using a Poisson model that assessed associations of sex, MSA, and month of onset of symptoms or month of diagnosis. Results: There were no significant seasonal patterns of disease onset in total IIM patients. Among MSAs, anti-synthetase (n=18), anti-transcriptional intermediary factor 1 γ (TIF1γ) (n=13), anti-melanoma differentiation-aasocianted protein 5 (anti-MDA5) (n=12), and anti–signal recognition particle (SRP) (n=12) were analyzed. Among 55 patients with dermatomyositis, patients with anti-MDA5 showed a significant peak in winter (n=12, P=0.05). This seasonal association was significant in women (n =10; P=0.045). Patients with anti–synthetase, anti-TIF1 γ or anti-SRP antibodies did not have a significant seasonal onset patterns. There were no significant seasonal patterns in patients without myositis-specific autoantibodies. Conclusion: Patients with anti-MDA5 showed a seasonality of myositis onset, in winter. Disclosure of interests: None declared