THU0354 CHARACTERIZATION OF ANTI-MYOSITIS ANTIBODY RELATED MYOPATHIES. DESCRIPTIVE STUDY IN A MULTICENTRIC COHORT.
Authors: S. López Salguero, M. Andres, P. Vela-Casasempere, A. Esteban Rodriguez, M. P. Martínez-Vidal, J. A. Bernal, A. Alvarez de Cienfuegos, F. Sivera
Journal: Annals of the Rheumatic Diseases (2020)

Background: Idiopathic inflammatory myopathies (IIM) are a group of rare diseases consisting on immune-mediated muscle damage. About 40 to 60% show specific-myositis antibodies; aditionally, 20-40% can show myositis-related (non-specific) antibodies. The profile of antibodies can help to divide patients into subgroups with more homogeneous clinical characteristics and prognosis. Objectives: This study characterizes patients with IIM with specific or related anti-myositis antibodies, in five hospitals in the Alicante health area. Methods: This is an observational study, carried out in five hospitals with a reference population of 1.083.463 people. Patients with positive anti-myositis antibodies between October 2015 and May 2018 were selected from the database of the Clinical Laboratory of the University Hospital of Alicante. We considered the following antiboides: anti-myositis specific antibodies (anti-TIF1y, anti-MDA5, anti-Mi-2, anti-PmScl75, anti-PMScl100, anti-NXP2, anti-SRP), anti-synthetase antibodies (anti-PL7, anti-PL12, anti-Jo1, anti-OJ), myositis-related antibodies (anti-Ro52, anti-Ku). Clinical records were examined, identifying those patients with a diagnosis of IIM acording to their clinician, rheumatologist. Epidemiological and clinical data were obtained. Results: 291 patients with positive anti-myositis antibodies were identified. Among them, 40 patients had a diagnosis of IIM. Median age was 59.5 (IQR 41.5, 70) years and 68% were women. Within the subgroups, the most frequent diagnosis were dermatomyositis (n=22; 55%) and polimyositis (n=9; 22%). The most common antibody detected was anti-TIF-y among specific antibodies, and anti-Jo-1 among the anti-synthetase antibodies. The most common extramuscular feature was skin involvement. The presence of interstitial lung disease was reported in about one third of patients, being UIP the most commong pattern. Regarding treatment, the use of steroids was generalized; methotrexate was the most used inmunosupresant agent. Eight patients had a cancer related myopathy. DM (N=22 ) PM (n=9 ) DMJ (N=3 ) IMNM (n=1 ) AS (n=5 ) Age, median (IQR ) 65,5(46, 76) 57(34, 66) 15,7 (14, 18) 83 (-) 61(56, 64) Female n(% ) 15(68,2) 6(66,6) 2(66,6) 1(100) 3(60) Muscular feat. n(% ) 16(77,7) 9(100) 1(33,3) 1(100) 5(100) ILD n(% ) 1(4,5) 3(33,3) 0 0 5(100) Disfagia n(% ) 3(13,6) 1(11,1) 0 0 0 Skin feat n(% ) 17(77,3) 0 2(66,6) 0 1(20) arthritis n(% ) 1(4,5) 0 2(66,6) 0 4(80) Raynaud n(% ) 4(19) 1(11,1) 0 0 1(20) Calcinosis n(% ) 1(4,5) 1(11,1) (66,6) 0 0 Puffy hands n (% ) 2(9) 0 0 0 2(40) Sicca synd n(% ) 3(13,6) 1(11,1) 0 0 0 Cáncer n(% ) 7(31,8) 1(11,1) 0 0 0 Ck máx(UI/l), median (IQR ) 432(171, 706) 809(350, 1653) - - 665(396, 2300) Conclusion: This register allows us to characterise patients with inflammatory myositis in our area. It is important to make multicentric and prospective registers in infrequent diseases such as IIM in order to have more detailed and representative information about clinical and socio-demographic characteristic as well as prognostic data from these patients. References: [1]Dalakas M. Inflammatory Muscle Diseasees. N Engl J Med 2015;372:1734-47. [2]Lündberg IE, Tjärnlund A, Bottai M, et al. 2017 Ann Rheum Dis2017;76:1955–1964. [3]Betteridge Z, McHugh N. J. Intern Med, 2016 Jul;280(1):8-23. [4]Nuño L et al. Reumatol Clin. 2017;13(6):331-337 [5]Lilleker JB, Vencovsky J, Wang G, et al.. Ann Rheum Dis 2018;77:30-39 Disclosure of Interests: None declared