Active secondary progressive multiple sclerosis

This code signifies a form of multiple sclerosis characterized by an initial relapsing-remitting course followed by a steady, progressive worsening of neurological function, with ongoing disease activity (e.g., new relapses, MRI activity). Patients experience accumulating disability without clear periods of remission, distinguishing it from primary progressive or relapsing-remitting forms.

Apply this code when documentation explicitly states "active secondary progressive multiple sclerosis." This diagnosis is typically made after a period of relapsing-remitting MS, and the "active" component indicates recent relapses or new MRI lesions. Supporting documentation includes neurological exam findings, MRI reports, and physician notes detailing disease progression and activity.

• Ensure documentation clearly specifies "active" to differentiate from G35.C0 (inactive secondary progressive MS).
• Do not use this code for primary progressive MS (G35.A) or relapsing-remitting MS (G35.B).
• Always sequence this code as the primary diagnosis when it is the reason for the encounter.