FY2027 ICD-10-CM reference
G21.9: Secondary parkinsonism, unspecified
By the HCC Buddy Coding Team
The official ICD-10-CM descriptor is Secondary parkinsonism, unspecified. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
Billable code. Verified against the official FY2027 order file.
FY2027 Tabular instructions
Instructions below include applicable chapter, section and parent-code notes. Each note identifies where it appears in the official source.
Excludes2
certain conditions originating in the perinatal period (P04-P96)
Source: G00-G99 (chapter, inherited).
Excludes2
certain infectious and parasitic diseases (A00-B99)
Source: G00-G99 (chapter, inherited).
Excludes2
complications of pregnancy, childbirth and the puerperium (O00-O9A)
Source: G00-G99 (chapter, inherited).
Excludes2
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
Source: G00-G99 (chapter, inherited).
Excludes2
endocrine, nutritional and metabolic diseases (E00-E88)
Source: G00-G99 (chapter, inherited).
Excludes2
injury, poisoning and certain other consequences of external causes (S00-T88)
Source: G00-G99 (chapter, inherited).
Excludes2
neoplasms (C00-D49)
Source: G00-G99 (chapter, inherited).
Excludes2
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Source: G00-G99 (chapter, inherited).
Excludes1
Huntington's disease (G10)
Source: G21 (category, inherited).
Excludes1
neurocognitive disorder with Lewy bodies (G31.83)
Source: G21 (category, inherited).
Excludes1
Shy-Drager syndrome (G90.3)
Source: G21 (category, inherited).
Excludes1
syphilitic Parkinsonism (A52.19)
Source: G21 (category, inherited).
Compare the FY2027 additions, removals and billable-status changes
What does G21.9 mean in FY2027?
The official ICD-10-CM descriptor is Secondary parkinsonism, unspecified. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
Is G21.9 billable in FY2027?
The FY2027 order file marks G21.9 as billable. Check the complete Tabular instructions and documentation before assigning it.
Does G21.9 map to an HCC?
In the CMS 2027 Initial ICD-10-CM Mappings (payment year 2027, 2026 dates of service), G21.9 maps to CMS-HCC V28 HCC 199 (Parkinson and Other Degenerative Disease of Basal Ganglia). For 2027 dates of service, CMS has not yet published the payment year 2028 mappings. ESRD, RxHCC, PACE and HHS-HCC mappings are still pending verification for FY2027.
Source: CMS FY2027 ICD-10-CM order file. Read the FY2027 Official Guidelines.
Review the FY2026 April edition