Question: How does secondary Parkinsonism differ from Parkinson’s disease, and what ICD-10 codes should we report for secondary Parkinsonism? Hawaii Subscriber Answer: Secondary Parkinsonism is similar to Parkinson’s disease; however, the symptoms are caused by certain medicines, a different nervous system disorder, or another illness. You have the following ICD-10 choices Parkinsonism: Don’t miss: Each code for secondary Parkinsonism excludes dementia with Parkinsonism (G31.83), Huntington’s disease (G10), Shy-Drager syndrome (G90.3), and syphilitic Parkinsonism (A52.19). Important: Since several of the secondary Parkinson’s ICD-10 codes direct you to report an additional code for adverse effects or to first code the drug or external agent causing the secondary Parkinsonism, you will want to make sure you carefully read all of the notes associated with these codes.