ICD-10 Code M05.642 – Rheumatoid arthritis of left hand with involvement of other organs and systems (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M05.642 – Rheumatoid arthritis of left hand with involvement of other organs and systems
What it is
This code identifies seropositive rheumatoid arthritis affecting the left hand, with documented involvement of other organs or systems. Use it when the record links the hand arthritis to systemic disease, not isolated joint pain.
Clinical signs
Typical findings include chronic inflammatory joint pain, swelling, stiffness, and reduced hand function. Clinical features vary; refer to documentation for evidence of systemic involvement such as extra-articular manifestations.
When to use this code
Use this code when the provider documents rheumatoid arthritis in the left hand and also notes involvement beyond the joints. It supports cases where the left hand is the specified site and the disease is not limited to a single localized joint problem. If laterality or systemic involvement is unclear, check documentation.
Do not use for
Do not use this code for unspecified rheumatoid arthritis, right-hand disease, or arthritis without documented systemic involvement. It is also not appropriate for non-rheumatoid inflammatory arthropathies.
Coding tip
Verify both laterality and the “with involvement of other organs and systems” wording before assigning M05.642.