P153 Characteristics of anti-melanoma differentiation-associated gene 5 positive dermatomyositis in Singapore

Abstract

Abstract Background/Aims Anti-melanoma differentiation-associated gene 5 (MDA5) Ab positive associated dermatomyositis (DM) patients with rapidly progressive-interstitial lung disease (RP-ILD) have poor survival rates. The aim of this study was to determine the various characteristics in Singaporean patients with anti-MDA5-Ab associated DM. Methods A chart review was undertaken of 84 DM patients with positive myositis specific antibodies, diagnosed between January 2015 to July 2019, at a major tertiary centre in Singapore. All had confirmed probable or definite DM according to the Bohan and Peter criteria, and only those with an International Myositis Classification Criteria score of at least 55% (probable idiopathic inflammatory DM) were included. Results 18 out of 84 were anti-MDA5-Ab positive (See Table 1 for summary). Features more common in the anti-MDA5 Ab positive vs. the anti-MDA5 Ab negative cohort included: inverse Gottron’s papules (27.8% vs. 3%, p = 0.001) palmar papules (27.8% vs. 0%, p < 0.001), violaceous rash (55.6% vs. 16.7%, p = 0.001), cutaneous ulcers (66.7% vs. 6.1%, p = <0.001), clinically amyopathic DM (50% vs. 22.7%, p = 0.023) and polyarthritis (38.9% vs. 12.1%, p = 0.0009). The anti-MDA5 Ab positive cohort had a lower median creatine kinase (IU/L) versus the anti-MDA5 Ab negative cohort; 328 [60-3254] vs. 1318 [61-36776], (p = 0.0027). ILD was more common in the anti MDA5 Ab positive vs. anti-MDA5 Ab negative cohort (61.1% vs. 34.8%; p = 0.044). Of these anti-MDA5 Ab positive with ILD, 45.5% had RP-ILD, 27.3% had either chronic ILD or asymptomatic ILD respectively. In contrast, only 17.4% had RP-ILD in the anti-MDA5 Ab negative cohort. The mortality rate in the anti-MDA5 Ab positive vs. negative cohort was higher (33.3% vs. 24.2%). Patients with both Ro-52 and MDA5 Ab positivity had a higher incidence of cutaneous ulcers, pneumothorax, ILD and mortality. Of those anti-MDA5-Ab positive cases that survived, treatment included either rituximab and/or tofacitinib. Conclusion In our population, anti-MDA5 Abs associated DM is a distinct clinical subset of DM and associated with increased mortality. Better recognition of these distinct clinical features will enable early diagnosis, risk stratification and aggressive treatment to improve survival. Disclosure J. Low: None. C. Chua: None. W. Lim: None. L. Koh: None. M. Manghani: None.