G21.2
Secondary parkinsonism due to other external agents
G21.2 (also written G212) is a billable ICD-10-CM diagnosis code for secondary parkinsonism due to other external agents. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 8 codes in category G21 (Secondary parkinsonism). The Alphabetic Index lists it under 1 entry. Its coding notes include a Code first instruction, 4 Excludes1 entries and 8 Excludes2 entries.
Code first
If the underlying condition listed here is present and known, sequence it first.
- (T51-T65) to identify external agent
Excludes1
Not coded here. The listed conditions generally should not be reported together.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (8 notes)
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
IRF 60% Rule
On the CMS list of diagnoses used to determine presumptive compliance with the IRF 60 percent rule.
Source: CMS IRF Presumptive Compliance-3, FY 2027 IRF PPS final rule files, effective for discharges on or after October 1, 2026Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 12 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CIPF Primary
IPF MS-DRG adjustment. A principal diagnosis of this code groups to one of these MS-DRGs. Which one depends on other facts of the stay, so the factor is a range:
| MS-DRG | Description | Factor |
|---|---|---|
| 056 | Degenerative nervous system disorders w MCC | 1.12 |
| 057 | Degenerative nervous system disorders w/o MCC | 1.11 |
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 1 entry