ICD-10 Code M05.80 – Other rheumatoid arthritis with rheumatoid factor of unspecified site (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M05.80 – Other rheumatoid arthritis with rheumatoid factor of unspecified site
What it is
This code identifies rheumatoid arthritis with a positive rheumatoid factor when the affected site is not specified and the diagnosis does not fit a more specific rheumatoid arthritis category. Use it when documentation confirms rheumatoid factor–positive RA but does not name a joint or other site.
Clinical signs
Typical findings include chronic inflammatory joint pain, swelling, stiffness, and reduced range of motion. Clinical features vary; refer to documentation, especially when the record confirms rheumatoid factor positivity but does not specify the involved site.
When to use this code
Use M05.80 when the provider documents rheumatoid arthritis with rheumatoid factor and leaves the site unspecified. It is appropriate for encounters where the note supports seropositive RA but does not identify a particular joint or body area. If a more specific site or subtype is documented, code that detail instead.
Do not use for
Do not use this code for rheumatoid arthritis without rheumatoid factor, or when the record identifies a more specific site. Check documentation if the diagnosis is unclear or if the note describes another inflammatory arthropathy.
Coding tip
Verify both rheumatoid factor positivity and the absence of a documented site before assigning M05.80.