SAT0514 Mri – guided therapy for systemic sclerosis associated myositis

Background Muscle involvement in systemic sclerosis (SSc) has a significant impact on morbidity, functional capacity, and mortality. The muscle histopathology is heterogeneous including inflammatory and fibrotic changes. Currently there are no satisfactory means to diagnose inflammatory myopathy in SSc pts with normal creatine kinase (CK) and to assess the response to therapy. Objectives Our aim was to evaluate whether muscle magnetic resonance imaging (MRI) might be a tool to diagnose inflammatory myopathy in SSc patients (pts) and to assess the effect of muscle oriented- immunomodulatory therapy. Methods We retrospectively analysed the clinical data of 290 consecutive SSc pts seen at our centre between the years 2012–2017. Our cohort is part of the EUSTAR registry (centre 042). Pts with muscle weakness as defined by the Medsger muscle severity score of ≥1 and at least one MRI study were included. Clinical data analyzis included SSc subtype, disease duration, modified Rodnan skin score (mRSS), Medsger muscle severity score, CK, autoantibody profile, MRI and immunomodulatory treatment. Results 26 pts with muscle weakness answered the criteria of Medsger muscle severity score of ≥1 MRI data were available, in 17 of the pts. Muscle oedema and fasciitis were seen in MRI in 13 pts (10 diffuse subset, median: age 40, disease duration 1.25 years, mRSS 13.5). MRI was normal in 4 pts (2diffuse SSc, median: age 50 years, disease duration 6 years, mRSS 4). CK was normal in 10 pts with pathologic MRI. Anti-topoisomerase was positive in 6 pts, RNA polymerase 3 – in 3 pts, anti-centromere – in 2 pts and 6 pts were only ANA positive. Muscle biopsy results were available in 4 pts: Biopsy was compatible with myositis in 3 pts with pathologic MRI and revealed fibrosis in 1 pt with normal MRI. 14 pts received immunomodulatory treatment: rituximab (3 pts), rituximab and intravenous immunoglobulins (IVIG) (3 pts), IVIG and methotrexate/azathioprine/mycophenolate mofetil.8 A second MRI was performed in 6 pts with first pathologic MRI, after 12 months of treatment. Significant regression of muscle oedema and perifasciitis was observed in 5 pts and correlated with clinical amelioration, with improvement of muscle strength. No clinical and imaging improvement occurred in one patient, despite the treatment. No change in muscle strength was seen in the patient with normal MRI and evidence of fibrosis on muscle biopsy, although the skin score improved. Conclusions MRI might serve as a non-invasive tool for diagnosis of inflammatory myopathy in SSc pts with early disease, Medsger muscle severity score of ≥1 and normal CK and for assessment of treatment efficacy. Disclosure of Interest None declared