Association of Fibrosing Myopathy in Systemic Sclerosis and Higher Mortality

Objective To determine if a unique subtype of scleroderma muscle disease exists by comparing the clinical features of systemic sclerosis ( SS c; scleroderma) patients with predominant fibrosis on muscle biopsy to those with inflammatory muscle histopathology. Methods This retrospective, cross‐sectional study included SS c patients with muscle weakness and an available muscle biopsy. Biopsies with fibrosis but without inflammation/necrosis were designated as “fibrosing myopathy,” and those with inflammation and/or necrosis were assigned a category of “inflammatory myopathy.” Clinical data, including features of SS c, serum creatine kinase ( CK ) levels, electromyography, autoantibody profile, and survival, were compared between the 2 groups. Results The study population consisted of 37 weak SS c patients, 8 with fibrosing myopathy and 29 with inflammatory myopathy. Compared to those with inflammatory myopathy, patients with fibrosing myopathy were more likely to have diffuse SS c skin subtype (87% versus 62%; P = 0.18), African American race (62.5% versus 37.9%; P = 0.20), and a lower mean ± SD forced vital capacity (55.5 ± 31.9 versus 66.4 ± 17.6; P = 0.23). They also had lower mean ± SD CK values (516 ± 391 versus 2,477 ± 3,511 IU /liter; P = 0.007) and lower aldolase values (13.8 ± 4.7 versus 27.3 ± 4.7; P = 0.01). Patients with fibrosing myopathy had a significantly higher mortality (5 of 8 [62.5%] versus 4 of 29 [14.3%]; P = 0.005). Conclusion Fibrosing myopathy is a unique histologic subtype of muscle disease among weak patients with SS c and is associated with significantly worse mortality compared to those with inflammation and/or necrosis on muscle biopsy.