Muscle involvement in the scleroderma syndromes. Muscle involvement was identified in 14 patients with scleroderma or a connective tissue disease overlap syndrome with predominant features of scleroderma. Patients presented with symmetrical proximal weakness indistinguishable from other inflammatory myopathies. Creatine kinase and electromyography were useful to demonstrate muscle involvement. Muscle histopathology demonstrated primarily the vasculopathy of scleroderma or polymyositis in similar numbers of patients. Scleroderma vasculopathy and polymyositis generally occur without specificity to diffuse scleroderma, the calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia syndrome, or an overlap syndrome with arthritis. Polymyositis also occurs when the vasculopathy of scleroderma involves other organ systems. 