AB0214\u2005MUSCLE INVOLVEMENT IN SYSTEMIC SCLEROSIS

Abstract

Background The prevalence of myopathy in systemic sclerosis (SSc) or scleroderma patients varies from 5% to 81% depending on the diagnostic criteria used to define the muscle involvement. The histopathological characteristics found in these patients and their correlation with the clinical features and autoantibody profile has not been fully characterized. Objectives To characterize the muscle involvement and histopathology findings in patients with SSc. Methods This retrospective cross-sectional study included all patients from Scleroderma Cohort of Vall d’Hebron General and Hospital Clínic de Barcelona with muscle biopsies available for review performed at the Muscle Research Unit of Hospital Clínic de Barcelona from May 2004 to November 2018. Muscle biopsies were performed, for weakness or raised CK and/or aldolase. Histological sections were independently evaluated by two myopathology experts looking for inflammation in the endomisium, perimisium and perivascular areas. The presence of necrosis, regeneration, fibrosis, neurogenic atrophy, and fiber type grouping as well as perifascicular atrophy were also recorded. Based on the autoantibody profiles patients were classified into five groups, “Scl70”, “PM/Scl”, “centromere”, “U1-RNP”, and “nucleolar and centromer IFI ANA pattern without specificity for anti-Scl70 or anticentromer”. Demographic and clinical data were obtained by chart review. Results 42 subjects were included, 33 (78,6%) of them were women. Considering the immunological profile 12 had Scl70, 12 PM/Scl, 5 anticentromere, 2 U1RNP, and 11 had ANA pattern without specificity for anti-Scl70 or anticentromer. Most of patients (90.5%) were Caucasians, 2 (4.8%) were Hispanic, and 2 of other ethnic background. The mean age at the onset of SSc was 42.1 (SD 2.5) years and at the muscular symptoms 50.7 (SD 2.1) years, respectively. Twenty-two (52.4%) patients presented with high CK level (mean level of 1316 ± 353.8 U/L; normal value ≥200 U/L) whereas 38 (90.5%) exhibited high aldolase level (mean 19 ± 2.53 U/L, normal value < 6 U/L). Of note, 17 (40.5%) presented with high aldolase level and normal CK. Regarding the clinical manifestations of muscle involvement, 34 (80%) patients developed symmetrical distribution. Twenty-six (61,9%) had interstitial lung disease and 5 (11.9%) patients developed cancer. Among the pathological features, 28 (66.7%) biopsies had fibrosis. Neurogenic atrophy was detected in 4 (9.5%) and fiber type grouping was present in 9 (21.4%) muscle biopsies. In near half of the muscle biopsies (45.2%) inflammatory infiltrate was present. Compared to other patients, those positive for PM/Scl had more perivascular (75%), endomysial (50%) and perimisial inflammation (75%) and perifascicular atrophy (42%) (all p< 0.05), while a reduced prevalence of inflammatory infiltrates was noted in the Scl70 group (17%) (p< 0.05). Conclusion In our cohort of SSc patients with muscle involvement, two main histopathological patterns were found, fibrosis and inflammation. Almost half patients presented with elevated aldolase with normal CK levels. The muscle disease heterogeneity suggests that a variety of pathologic mechanisms play a role in the scleroderma associated myopathy but those patients with histopathological inflammatory features deserve to be treated with immunosuppressive therapy. References [1] Arthritis Care Res (Hoboken). 2015; 67: 1416-25 [2] Ther Adv Musculoskelet Dis. 2017; 9: 3–10. [3] Arthritis Res Ther. 2014; 16: R111. Disclosure of Interests None declared