ICD-10-CM Code For Secondary Parkinsonism: Group Overview

The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code group G21 includes parkinsonism syndromes caused by medications, toxins, metabolic conditions, structural brain lesions, or other identifiable nonidiopathic causes, and it covers clinical presentations with bradykinesia, rigidity, tremor, and gait disturbances. These ICD-10-CM diagnosis codes are used to document secondary parkinsonism etiologies, capture disease severity and neurologic involvement, and distinguish these disorders from idiopathic Parkinson disease. Accurate coding within the ICD-10-CM G21 group supports proper claim adjudication, complete clinical documentation, and appropriate reimbursement.

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ICD-10-CM G21: Secondary Parkinsonism Overview

The International Classification of Diseases, Tenth Revision, Clinical Modification code group G21 covers secondary parkinsonism conditions that result from identifiable causes such as medications, toxins, metabolic disorders, or structural brain lesions. These disorders affect the extrapyramidal motor system and produce parkinsonian features including bradykinesia, rigidity, tremor, and postural instability. Accurate coding matters for reimbursement because it links clinical documentation to specific etiologies and supports appropriate claim adjudication.

When to Use

Assign a code from this group when clinical documentation specifies parkinsonism attributable to a known external or systemic cause rather than idiopathic Parkinson disease. Use these codes to reflect the specific etiology when documentation links motor symptoms to a medication, toxin exposure, metabolic disorder, or brain lesion.

ICD-10-CM Codes

8 rows

ICD-10-CM Code	Description
G21.0	Malignant neuroleptic syndrome
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
G21.4	Vascular parkinsonism
G21.8	Other secondary parkinsonism
G21.9	Secondary parkinsonism, unspecified

DRG Codes

5 rows

DRG Code	Description
056	Degenerative Nervous System Disorders with MCC
057	Degenerative Nervous System Disorders without MCC
091	Other Disorders of Nervous System with MCC
092	Other Disorders of Nervous System with CC
093	Other Disorders of Nervous System without CC/MCC

Typical Clinical Scenarios

An older adult with a known history of long-term antipsychotic use presents with new-onset bradykinesia, rigidity, and resting tremor over weeks to months, impairing gait and activities of daily living; medication history and exam suggest drug-induced parkinsonism rather than idiopathic Parkinson disease, so a secondary parkinsonism diagnosis related to medication effect is assigned. Typical codes: G21.11, G21.9
A middle-aged patient hospitalized after a severe carbon monoxide poisoning event develops subacute parkinsonian features including masked facies, slowed movements, and postural instability during the recovery phase; these neurologic sequelae are attributed to the toxic brain injury and coded as secondary parkinsonism due to toxic/metabolic cause. Typical codes: G21.2, G21.9
A patient with documented progressive supranuclear palsy–type picture or another neurodegenerative disorder with parkinsonism features is seen for chronic management of movement symptoms that are not idiopathic Parkinson disease; the clinician records secondary parkinsonism to indicate parkinsonian signs attributable to the underlying neurodegenerative condition or structural lesion rather than primary Parkinson disease. Typical codes: G21.3, G21.9}

Related Codes

G20-PARKINSONS-DISEASE

ICD-10-CM Code For Parkinsons Disease: Group Overview

G23-OTHER-DEGENERATIVE-DISEASES-BASAL-GANGLIA

ICD-10-CM Code For Other Degenerative Diseases Of Basal Ganglia: Group Overview

G24-DYSTONIA

ICD-10-CM Code For Dystonia: Group Overview

G25-OTHER-EXTRAPYRAMIDAL-MOVEMENT-DISORDERS

ICD-10-CM Code For Other Extrapyramidal And Movement Disorders: Group Overview

G26-EXTRAPYRAMIDAL-AND-MOVEMENT-DISORDERS

ICD-10-CM Code For Extrapyramidal And Movement Disorders In Diseases Classified Elsewhere: Group Overview

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.

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When to Use

ICD-10-CM Codes

8 rows

ICD-10-CM Code	Description
G21.0	Malignant neuroleptic syndrome
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
G21.4	Vascular parkinsonism
G21.8	Other secondary parkinsonism
G21.9	Secondary parkinsonism, unspecified

DRG Codes

5 rows

DRG Code	Description
056	Degenerative Nervous System Disorders with MCC
057	Degenerative Nervous System Disorders without MCC
091	Other Disorders of Nervous System with MCC
092	Other Disorders of Nervous System with CC
093	Other Disorders of Nervous System without CC/MCC

Typical Clinical Scenarios

An older adult with a known history of long-term antipsychotic use presents with new-onset bradykinesia, rigidity, and resting tremor over weeks to months, impairing gait and activities of daily living; medication history and exam suggest drug-induced parkinsonism rather than idiopathic Parkinson disease, so a secondary parkinsonism diagnosis related to medication effect is assigned. Typical codes: G21.11, G21.9
A middle-aged patient hospitalized after a severe carbon monoxide poisoning event develops subacute parkinsonian features including masked facies, slowed movements, and postural instability during the recovery phase; these neurologic sequelae are attributed to the toxic brain injury and coded as secondary parkinsonism due to toxic/metabolic cause. Typical codes: G21.2, G21.9
A patient with documented progressive supranuclear palsy–type picture or another neurodegenerative disorder with parkinsonism features is seen for chronic management of movement symptoms that are not idiopathic Parkinson disease; the clinician records secondary parkinsonism to indicate parkinsonian signs attributable to the underlying neurodegenerative condition or structural lesion rather than primary Parkinson disease. Typical codes: G21.3, G21.9}

Related Codes

G20-PARKINSONS-DISEASE

ICD-10-CM Code For Parkinsons Disease: Group Overview

G23-OTHER-DEGENERATIVE-DISEASES-BASAL-GANGLIA

ICD-10-CM Code For Other Degenerative Diseases Of Basal Ganglia: Group Overview

G24-DYSTONIA

ICD-10-CM Code For Dystonia: Group Overview

G25-OTHER-EXTRAPYRAMIDAL-MOVEMENT-DISORDERS

ICD-10-CM Code For Other Extrapyramidal And Movement Disorders: Group Overview

G26-EXTRAPYRAMIDAL-AND-MOVEMENT-DISORDERS

ICD-10-CM Code For Extrapyramidal And Movement Disorders In Diseases Classified Elsewhere: Group Overview

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

ICD-10-CM Code For Secondary Parkinsonism: Group Overview

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ICD-10-CM G21: Secondary Parkinsonism Overview

ICD-10-CM Code For Secondary Parkinsonism: Group Overview

Sign up for ICD-10-CM Code For Secondary Parkinsonism: Group Overview policy alerts

ICD-10-CM G21: Secondary Parkinsonism Overview

When to Use

ICD-10-CM Codes

DRG Codes

Typical Clinical Scenarios

Related Codes

Which conditions are included in ICD-10-CM code group `G21`?

What specific ICD-10-CM codes appear in the `G21` group?

Why is accurate coding within `G21` important for reimbursement?

How does `G21` help distinguish disorders from idiopathic Parkinson disease?

Which related DRGs may be impacted by coding a `G21` diagnosis?

References

When to Use

ICD-10-CM Codes

DRG Codes

Typical Clinical Scenarios

Related Codes

Which conditions are included in ICD-10-CM code group `G21`?

What specific ICD-10-CM codes appear in the `G21` group?

Why is accurate coding within `G21` important for reimbursement?

How does `G21` help distinguish disorders from idiopathic Parkinson disease?

Which related DRGs may be impacted by coding a `G21` diagnosis?

References