G21.0 Malignant neuroleptic syndrome

Billable ICD-10-CM code, FY2026. Acts as a Major Complication or Comorbidity (MCC) as a secondary diagnosis.

Excludes1 (never code together)

• neuroleptic induced parkinsonism (G21.11)

Use additional code

• code for adverse effect, if applicable, to identify drug (T43.3X5, T43.4X5, T43.505, T43.595)

Applies from G21 Secondary parkinsonism

Excludes1 (never code together)

• Huntington's disease (G10)
• neurocognitive disorder with Lewy bodies (G31.83)
• Shy-Drager syndrome (G90.3)
• syphilitic Parkinsonism (A52.19)

MS-DRG index

Defines the logic of DRG(s) 091-093 in MDC 01.

Approximate ICD-9-CM (GEMs)

• 333.92 Neuroleptic malignant syndrome

Code annotations containing back-references to G21.0

Back-references to G21.0

• Type 1 Excludes: G21.11 Neuroleptic induced parkinsonism ("malignant neuroleptic syndrome (G21.0)")

Back-references to G21

• Type 2 Excludes: F98.4 Stereotyped movement disorders ("movement disorders of organic origin (G20-G25)")
• Type 1 Excludes: G20.C Parkinsonism, unspecified ("secondary parkinsonism (G21.-)")
• Type 1 Excludes: R25 Abnormal involuntary movements ("specific movement disorders (G20-G26)")

Diagnosis Index entries for G21.0

• Syndrome › malignant › neuroleptic

Nearby codes

• G21 Secondary parkinsonism
• G21.0 Malignant neuroleptic syndrome (this code)
• G21.1 Other drug-induced secondary parkinsonism
• G21.11 Neuroleptic induced parkinsonism
• G21.19 Other drug induced secondary parkinsonism
• G21.2 Secondary parkinsonism due to other external agents
• G21.3 Postencephalitic parkinsonism