HCC 199: Parkinson and Other Degenerative Disease of Basal Ganglia ICD-10-CM
CMS-HCC Category 199 (Parkinson and Other Degenerative Disease of Basal Ganglia) is a payment HCC in the V28 Medicare Advantage risk adjustment model. For payment year 2026 it adds a risk adjustment factor between 0.219 and 0.634 to a beneficiary's RAF score depending on the payment segment (0.615 for a community, non-dual, aged enrollee). 16 ICD-10-CM diagnosis codes map to HCC 199. It sits at the top of its hierarchy: no other condition category supersedes it.
RAF Weight by Payment Segment 7 segments
| Payment Segment | Relative Factor |
|---|---|
| Community, non-dual, aged | 0.615 |
| Community, partial-benefit dual, aged | 0.474 |
| Community, full-benefit dual, aged | 0.634 |
| Community, non-dual, disabled | 0.517 |
| Community, partial-benefit dual, disabled | 0.354 |
| Community, full-benefit dual, disabled | 0.504 |
| Institutional | 0.219 |
A beneficiary is scored in exactly one segment, set by Medicaid (dual) status, aged or disabled entitlement, and residence. Factors are relative weights, not dollar amounts; new-enrollee segments score on demographics only. HCC 199 neither supersedes nor is superseded by any other category, so it always counts alongside unrelated HCCs.
ICD-10-CM Codes That Map to HCC 199 16 codes
- G20.A1 Parkinson's disease without dyskinesia, without mention of fluctuations from V24 HCC 78
- G20.A2 Parkinson's disease without dyskinesia, with fluctuations from V24 HCC 78
- G20.B1 Parkinson's disease with dyskinesia, without mention of fluctuations from V24 HCC 78
- G20.B2 Parkinson's disease with dyskinesia, with fluctuations from V24 HCC 78
- G20.C Parkinsonism, unspecified from V24 HCC 78
- G21.3 Postencephalitic parkinsonism from V24 HCC 78
- G21.4 Vascular parkinsonism from V24 HCC 78
- G21.8 Other secondary parkinsonism from V24 HCC 78
- G21.9 Secondary parkinsonism, unspecified from V24 HCC 78
- G23.0 Hallervorden-Spatz disease from V24 HCC 78
- G23.1 Progressive supranuclear ophthalmoplegia [Steele-Richardson-Olszewski] from V24 HCC 78
- G23.2 Striatonigral degeneration from V24 HCC 78
- G23.3 Hypomyelination with atrophy of the basal ganglia and cerebellum from V24 HCC 78
- G23.8 Other specified degenerative diseases of basal ganglia from V24 HCC 78
- G23.9 Degenerative disease of basal ganglia, unspecified from V24 HCC 78
- G90.3 Multi-system degeneration of the autonomic nervous system from V24 HCC 78
Every code above carries the full HCC 199 weight when documented and reported on a Medicare Advantage encounter. The code link opens its full page with the complete risk adjustment card.
Questions About HCC 199
What is HCC 199 in the CMS-HCC model?
HCC 199 is CMS-HCC Category 199 (Parkinson and Other Degenerative Disease of Basal Ganglia) in the V28 risk adjustment model. It covers 16 ICD-10-CM diagnosis codes that raise a Medicare Advantage beneficiary's risk score when documented.
What is the RAF weight for HCC 199?
For payment year 2026, HCC 199 adds 0.615 to the RAF score of a community, non-dual, aged beneficiary. The published weights range from 0.219 to 0.634 across the seven payment segments shown above.
Related References
Source: Centers for Medicare & Medicaid Services, Payment Year 2026 risk adjustment mapping and model software releases (CMS-HCC V28), applied to the FY 2026 ICD-10-CM code set. ICD List is not affiliated with CMS.
