Myopathy in diseases classified elsewhere

This code signifies a muscle disease (myopathy) that arises as a secondary complication or manifestation of another underlying systemic disease. It indicates that the primary disease is responsible for the muscle dysfunction, rather than the myopathy being a standalone, primary condition.

Use this code when documentation clearly links a patient's myopathy to an underlying systemic disease that is classified elsewhere in ICD-10-CM. This typically applies when the myopathy is not an inherent part of the primary disease's code description or when the primary disease has a specific code for its myopathic manifestation. The medical record should explicitly state the causal relationship between the systemic disease and the myopathy.

• Always sequence the underlying systemic disease first, followed by this code.
• Carefully review the "Excludes1" notes to avoid incorrect co-coding with specific myopathies already integrated into other disease codes.
• Ensure the documentation specifies the type of myopathy (e.g., inflammatory, toxic) if known, as this may influence the primary disease code choice or provide further specificity.