Muscle involvement in systemic sclerosis: high mortality not associated with nature of histological lesions

Objectives: The aim of this study was to determine the association between various histological patterns and prognosis in patients with SSc and histologically proven muscle involvement. Methods: A multicentre retrospective study was conducted of a cohort of scleroderma patients who had undergone muscle biopsy. The biopsies were reviewed in a coordinated manner to classify patients based on the histological findings. Three different patterns were observed: fibrosing myopathy (FMy), inflammatory myopathy (IMy), and immune-mediated necrotizing myopathy (IMNMy). Rates of survival, muscle relapse, and cardiac and pulmonary events were compared between these three groups. Results: Among the 71 scleroderma patients with muscle biopsy specimens available for review, 33 (46.5%) were classified in the FMy group, 18 (25.5%) in the IMy group and 20 (28%) in the NMy group. The median follow-up time was 6.4 years (interquartile range, 2.2-10.9 years), and 21 patients died during follow-up, primarily from heart disease and infections. The 10-year survival rate after the first non-RP symptom was 80%, and the cumulative incidence of muscle relapse was 25%. Neither factor differed significantly between the three groups. The risk of pulmonary events was lowest in the IMy group, significantly lower than in the FMy group (hazard ratio, 0.17; 95% CI, 0.04-0.67) and non-significantly lower than in the IMNMy group (hazard ratio, 0.28; 95% CI, 0.06-1.24). The risk of cardiac events did not differ significantly between the three groups. Conclusion: The mortality rate in scleroderma patients with muscle involvement was not associated with their histological patterns. [GRAPHICS] .