Myopathies related to systemic sclerosis: a case-control study of associated clinical and immunological features

Little is known about systemic sclerosis (SSc)-related myopathy. We aimed to compare the clinical and immunological features of SSc patients with or without associated myopathy.

Forty SSc patients with myopathy, defined by myalgia or muscle weakness associated with creatine kinase (CK) more than five times the upper limit range or myopathic electromyography (EMG) or abnormal myopathology, were identified from the records of four French hospital centres. For each patient, we selected two SSc controls matched for cutaneous SSc form, sex, age at SSc onset, and disease duration. We performed a case-control study testing clinical and immunological SSc-related features for association with myopathy by conditional logistic regression.

Muscle and SSc features of patients with myopathy did not differ significantly among the four centres of origin. Only four (10%) patients with SSc-associated myopathy had anti-polymyositis-scleroderma (PM-Scl) antibodies. Case-control univariate analysis revealed that reduced forced vital capacity (FVC) [odds ratio (OR) 3.0, 95% confidence interval (CI) 1.3-34.9], heart involvement, defined as clinical congestive heart failure, left ventricular ejection fraction (LVEF) < 60%, arrhythmia or conductive abnormalities (OR 2.9, 95% CI 1.3-6.5), and scleroderma renal crisis (OR 3.0, 95% CI 1.3-34.9) were significantly more frequent in patients with myopathy than in controls. Two autoantibodies were more frequent in patients with myopathy: anti-PM-Scl (OR 5.0, 95% CI 1.1-23.9) and anti-RNP (OR 6.9, 95% CI 1.1-64.4). Multivariate analysis retained two variables associated positively with myopathy [reduced FVC (OR 3.1, 95% CI 1.3-9.8) and heart involvement (OR 2.5, 95% CI 1.1-7.1)], while anti-centromere antibodies were associated negatively (OR 0.11, 95% CI 0.03-0.53).

Heart monitoring of SSc patients with myopathy should be undertaken regularly because of the association of myocardial and skeletal myopathies in such patients.