ICD-10 Code B26.85 – Mumps arthritis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B26.85 – Mumps arthritis
What it is
B26.85 identifies arthritis caused by mumps infection. Use it when joint inflammation is documented as a complication of mumps rather than as a separate rheumatic condition.
Clinical signs
Clinical features vary; refer to documentation. Typical findings include joint pain, swelling, stiffness, and reduced range of motion occurring with or after mumps infection.
When to use this code
Use B26.85 when the provider links arthritis directly to mumps, such as in a patient with confirmed mumps and documented inflammatory joint involvement. You should code the condition when the record clearly states mumps arthritis or an equivalent diagnosis.
Apply it for acute infectious arthritis associated with mumps, not for nonspecific arthralgia or unrelated joint disease. Check documentation if the note does not explicitly connect the arthritis to mumps.
Do not use for
Do not use this code for joint pain without documented arthritis, or for arthritis caused by another infection or chronic rheumatic disorder. Check documentation when the cause is unclear.
Coding tip
Confirm that mumps is documented as the cause of the arthritis before assigning B26.85.