THU0410 Survival of patients with muscle biopsy proven idiopathic inflammatory myopathy based on a study in a tertiary university centre
Authors: K. Gulyás, E. Pál, T. Minier, T. Berki, L. Czirják, C. Varjú
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Idiopathic inflammatory myopathies (IIM) are characterised by muscle weakness due to muscle inflammation, various organ involvements and the presence of certain specific autoantibodies. <h3>Objectives</h3> To assess survival and characterise subsets based on muscle biopsy and myositis specific autoantibodies. <h3>Methods</h3> Eighty-two patients with muscle biopsy proven IIM were included in the study. Muscle biopsy was reevaluated and cathegorized by the same investigator (EP). All cases had myositis specific (MSA) and myositis associated (MAA) antibody tests. The MSAs and MAAs (Jo-1, PL-7, PL-12, Mi-2, SRP, Pm-Scl, Ku, ribosomal, AMA-M2) were tested with Western-blot. Dermatomyositis/DM/, polymyositis/PM/, juvenile PM/DM, inclusion body myositis/IBM/, overlap myositis/OM/ and immune mediated necrotizing myopathy/IMNM/were identified based on clinical data, immunserology and muscle biopsy. Patients were treated with glucocorticoids/cytostatics, interstitial lung disease was treated with pulse cyclophosphamide in 15/43 cases. Survival analysis was perfomed by Kaplan Meier test. <h3>Results</h3> Fifty-nine women and 23 men with a mean age of 49.3±14.6 years were included. Mean follow-up of the patients was 7.5±4.5 years. Interstitial lung disease (ILD) (51.2%), arthritis (51.2%), Raynaud's phenomenon (42.7%), skin symptoms (45.1%), dysphagia (24.4%) and significant cardiac involvement (15.9%) were the most prevalent disease manifestations. 15 cases were associated with malignancies. The distribution of myositis subsets is as follows: 26.8% (n=22) PM, 30.5% (n=25) DM, 1.2% (n=1) juvenile PM/DM, 8.5% (n=7) IBM, 22% (n=18) OM, and 11% (n=9) IMNM. Malignancy was most frequently associated with IMNM (7 out of 9 patients). Altogether 18 patients died from which 15 deaths can be connected to myositis related events. Eight patients died of malignancies (4 in the IMNM, 2 in the PM and 2 in the DM group), 5 patients due to cardiac events (heart failure, arrythmia), 2 due to lung fibrosis and 3 by unknown causes. The worst prognosis with a 10 year survival of 31% was in the IMNM subgroup (p&lt;0.01), followed by patients with PM (68%), IBM (84%) OM (85.1%) and DM (85.3%). Mi-2 positive patients had a favourable prognosis with a 10 year survival of 100. Patients with muscle histology corresponding with IMNM had the worst prognosis (10 year survival of 31.1%), followed by PM (76%), DM and IBM (85.7% each). Non specific muscle changes unclassifiable to any of the previous groups were associated with a relatively favourable prognosis (5 year survival of 80%) (p&lt;0.01). Patients with antisynthetase antibody-positivity had worse prognosis compared with patients with other antibodies or no identifiable antibodies (10 year survival of 55%, n=16) (p&lt;0.05). When comparing patients with MSA or MAA, the worst prognosis was seen in patients with both MSA and MAA positivity (10 year survival of 35.6%, n=10). <h3>Conclusions</h3> The worst survivals were seen in the IMNM and PM groups, due to the high frequency of the underlying malignancies and cardiac manifestations. Although ILD was the most frequent involvement, it was not a major determinant of outcome. <h3>Disclosure of Interest</h3> None declared