Other myositis, other site

This code signifies an inflammatory condition of muscle tissue (myositis) that does not fit into more specific categories of myositis and affects a site other than those explicitly classified elsewhere. It encompasses various forms of myositis that are not infectious, toxic, or otherwise specified, presenting with muscle pain, weakness, and inflammation.

Use this code when documentation indicates myositis that is not clearly identified as dermatomyositis, polymyositis, inclusion body myositis, or other specified types, and the affected muscle group is not explicitly defined by a more specific code. Supporting documentation should detail the myositis and rule out more specific etiologies or anatomical sites.

• Ensure documentation clearly states "other myositis" or provides insufficient detail for a more specific myositis code.
• Always review for a more specific myositis code (e.g., M33.x for dermatomyositis/polymyositis) before assigning this code.
• Do not use for myositis due to infection or toxic agents; these have specific codes within Chapter 1.