ICD-10 Code M05.4 – Rheumatoid Myopathy with Rheumatoid Arthritis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M05.4 – Rheumatoid myopathy with rheumatoid arthritis
What it is
This code identifies rheumatoid arthritis complicated by myopathy, meaning muscle weakness or muscle disease occurring with the rheumatoid condition. Use it when the record documents both rheumatoid arthritis and a related muscle disorder.
Clinical signs
Typical findings include proximal muscle weakness, reduced endurance, and functional difficulty such as rising from a chair or lifting objects. Clinical features vary; refer to documentation for evidence that the muscle problem is associated with rheumatoid arthritis.
When to use this code
Use M05.4 when the provider documents rheumatoid arthritis with myopathy, myositis, or another rheumatoid-related muscle involvement. The chart should support both the rheumatoid diagnosis and the muscle condition; check documentation if the relationship is unclear.
Do not assign it for generalized weakness alone or for muscle symptoms without a documented rheumatoid connection. If the record mentions rheumatoid arthritis but no myopathy, choose the more specific rheumatoid arthritis code instead.
Do not use for
Do not use this code for rheumatoid arthritis without muscle involvement, or for nonspecific weakness without a documented myopathy. Check documentation if another neuromuscular disorder is the actual reason for the visit.
Coding tip
Confirm that the provider links the muscle disorder to rheumatoid arthritis before coding M05.4.