How is myopathy characterized in comparison to polymyositis?

Myopathy, in general, is characterized primarily by muscle weakness that is not accompanied by tenderness. This is an essential differentiating factor, particularly when comparing it to polymyositis, which specifically presents as muscle weakness along with muscle tenderness and inflammation. Patients with polymyositis will generally experience not only weakness but also discomfort and pain in the affected muscles due to inflammatory processes.

In contrast, while myopathy may involve various forms and underlying causes (such as metabolic, genetic, or toxic factors), the defining characteristic is the weakness itself, which can occur without any noticeable pain or tenderness in the muscles. This lack of tenderness in myopathy helps distinguish it from conditions like polymyositis, where tenderness is a prominent feature.

The other choices highlight symptoms that do not align with the fundamental characteristics of myopathy. Localized pain and swelling suggest an inflammatory process, while severe muscle cramps indicate a different mechanism altogether and are not typically associated with myopathy.