Abstract

Patients with systemic sclerosis (SSc) frequently report muscle weakness. The prevalence of muscle involvement in SSc, however, varies largely, and numbers range from 5-96%. Muscle weakness due to direct involvement of skeletal muscles in the disease process needs to be distinguished from myopathy secondary to disuse (fatigue, articular disease, cardiopulmonary involvement), cachectic atrophy, or from medications (statins, antimalarials etc.). Laboratory features such as elevation of muscle enzymes in patients’ serum may additionally contribute to the varying prevalence since in some patients, muscle enzymes may be only moderately elevated or be completely within normal limits despite the simultaneous myopathy as proven by a myopathic electromyogram (EMG) or a skeletal muscle biopsy. Furthermore, there is no consensus whether or not an inflammatory myopathy in SSc should be merely considered as an organ complication of SSc or as SSc-myositis overlap.

To illustrate possible pitfalls in diagnosing SSc-associated myopathy and scleroderma-polymyositis overlap, we will present two different cases by highlighting the clinical symptoms and diagnostic procedures and discuss current treatment options.

Based on the two case studies, we will demonstrate that the aetiology of SSc-associated myopathy is heterogenous and that there is an unmet need for the development of diagnostic consensus criteria, treatment recommendations and outcome measures.