ICD-10-CM > G00-G99 > G20-G26 > G21 G21 Secondary parkinsonism Non-Billable/Non-Specific Type 1 Excludes Huntington's disease (G10)neurocognitive disorder with Lewy bodies (G31.83)Shy-Drager syndrome (G90.3)syphilitic Parkinsonism (A52.19) Codes G21.0Malignant neuroleptic syndromeG21.1Other drug-induced secondary parkinsonismG21.11Neuroleptic induced parkinsonismG21.19Other drug induced secondary parkinsonismG21.2Secondary parkinsonism due to other external agentsG21.3Postencephalitic parkinsonismG21.4Vascular parkinsonismG21.8Other secondary parkinsonismG21.9Secondary parkinsonism, unspecified