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ICD-10-CM 2027 diagnosis code

G21.2Secondary parkinsonism due to other external agents

✓ Billable / specificCC — complication/comorbidity

G21.2 is a valid, billable ICD-10-CM code for secondary parkinsonism due to other external agents. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About G21.2

G21.2 is the ICD-10-CM diagnosis code for secondary parkinsonism due to other external agents. It belongs to category G21 (secondary parkinsonism), block G20-G26 (extrapyramidal and movement disorders) and chapter 6 (diseases of the nervous system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within G21, choose G21.2 (due to other external agents) only when documentation doesn't support a more specific option: malignant neuroleptic syndrome (G21.0), other drug-induced secondary parkinsonism (G21.1), Postencephalitic parkinsonism (G21.3), vascular parkinsonism (G21.4), other secondary parkinsonism (G21.8) and unspecified (G21.9).

Code first: (T51-T65) to identify external agent.

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 056 (Degenerative Nervous System Disorders with MCC, relative weight 2.2655) and DRG 057 (Degenerative Nervous System Disorders without MCC, relative weight 1.2838), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 332.1 (secondary parkinsonism).

Coding notes

Code firstSequence the underlying condition first
  • (T51-T65) to identify external agent

Notes that apply from higher levels

Instructions written at a parent level also apply to G21.2.

› From G21 Secondary parkinsonism
Excludes1
  • Huntington's disease (G10)
  • neurocognitive disorder with Lewy bodies (G31.83)
  • Shy-Drager syndrome (G90.3)
  • syphilitic Parkinsonism (A52.19)

Broader instructions also apply from Chapter 6: Diseases of the nervous system.

Alphabetic index entries

1 entries

Terms in the official ICD-10-CM index that lead to G21.2.

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 332.1Secondary parkinsonismapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about G21.2

Is G21.2 billable?

Yes. G21.2 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can G21.2 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict G21.2 as a principal diagnosis.

Is G21.2 a CC or MCC?

G21.2 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does G21.2 group to?

G21.2 is used in the MS-DRG v44.0 logic for MS-DRG 056 (Degenerative Nervous System Disorders with MCC) and MS-DRG 057 (Degenerative Nervous System Disorders without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for G21.2?

The CMS General Equivalence Mappings map G21.2 to ICD-9-CM 332.1.