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

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.

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.

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.

The mortality rate in scleroderma patients with muscle involvement was not associated with their histological patterns.