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 HCC 199 neither supersedes nor is superseded by any other category, so it always counts alongside unrelated HCCs.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 (living at home, age 65 or over, not also enrolled in Medicaid). 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.
