Muscle Disease in systemic lupus erythematosus: a study of its nature, frequency and cause.

The nature, frequency and cause of clinical features suggesting muscle involvement in systemic lupus erythematosus were studied in 20 patients during "active" disease. Half of these patients experienced varying combinations of myalgia, proximal muscle weakness and muscle tenderness. This group "with muscle features" had a higher incidence of arthralgia and much of their myalgia may simply have been due to pain referred from adjacent joints. However, a greater number of abnormalities were also found in the muscle biopsies of this group and it is likely that polymyositis and steroid myopathy were important contributory factors.