ICD-10 Code G35.C1 – Active secondary progressive multiple sclerosis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G35.C1 – Active secondary progressive multiple sclerosis
What it is
This code identifies secondary progressive multiple sclerosis with active disease. Use it when the record shows ongoing progression and evidence of inflammatory activity or relapses.
Clinical signs
Patients may have worsening neurologic disability over time, with or without superimposed relapses. Clinical features vary; refer to documentation for signs of active disease, such as new neurologic deficits or MRI activity.
When to use this code
Use G35.C1 when the provider documents active secondary progressive MS, not just a history of MS or a nonactive progressive course. It is appropriate when the note clearly states secondary progressive disease with current activity. Check documentation if the subtype or activity status is unclear.
Do not use for
Do not use this code for relapsing-remitting MS, primary progressive MS, or inactive secondary progressive MS. If the record only says “multiple sclerosis” without subtype or activity, check documentation.
Coding tip
Verify both the progressive subtype and the active status before assigning G35.C1.