Parkinson and Other Degenerative Disease of Basal Ganglia
Under the CMS-HCC V28 risk adjustment model (PY2026 Medicare Advantage), HCC 199 carries a community non-dual aged RAF of 0.615, and 16 payable ICD-10-CM diagnosis codes map to it.
Medically reviewed by Jess P., CPC · Reviewed: May 30, 2026
RAF factors
The community factor varies by Medicaid and originally-disabled status; the institutional factor applies to long-term-institutional members. These are the CMS-HCC V28 PY2026 relative factors.
Combine this factor with demographics and other HCCs in the RAF score calculator to model the full CMS-HCC V28 RAF for a member.
ICD-10-CM codes that map to HCC 199 (16)
Payable diagnosis codes that map to this category under CMS-HCC V28 PY2026. Open any code for its full description, HCC mapping, and coding guidance.
- G20.A1Parkinson's disease without dyskinesia, without mention of fluctuations
- G20.A2Parkinson's disease without dyskinesia, with fluctuations
- G20.B1Parkinson's disease with dyskinesia, without mention of fluctuations
- G20.B2Parkinson's disease with dyskinesia, with fluctuations
- G20.CParkinsonism, unspecified
- G21.3Postencephalitic parkinsonism
- G21.4Vascular parkinsonism
- G21.8Other secondary parkinsonism
- G21.9Secondary parkinsonism, unspecified
- G23.0Hallervorden-Spatz disease
- G23.1Progressive supranuclear ophthalmoplegia [Steele-Richardson-Olszewski]
- G23.2Striatonigral degeneration
- G23.3Hypomyelination with atrophy of the basal ganglia and cerebellum
- G23.8Other specified degenerative diseases of basal ganglia
- G23.9Degenerative disease of basal ganglia, unspecified
- G90.3Multi-system degeneration of the autonomic nervous system
Coder workflow notes
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Frequently asked questions
What is CMS-HCC V28 category 199?
HCC 199 is "Parkinson and Other Degenerative Disease of Basal Ganglia", a payment Hierarchical Condition Category in the CMS-HCC V28 risk adjustment model (100% phase-in for payment year 2026). 16 payable ICD-10-CM codes map to it.
What is the RAF weight for HCC 199?
The community non-dual aged relative factor for CMS-HCC V28 category 199 is 0.615. The exact factor varies by enrollment segment (community Medicaid and originally-disabled status, and institutional); the full segment table is published in the CMS V28 Rate Announcement.
How many ICD-10-CM codes map to HCC 199?
16 payable ICD-10-CM diagnosis codes map to CMS-HCC V28 category 199 (Parkinson and Other Degenerative Disease of Basal Ganglia) for payment year 2026.
Related references
Sources
CMS published ICD-10-CM mapping file plus CMS-HCC v28 PY2026 model software. CMS-HCC V28 model published at CMS.gov Risk Adjustors; ICD-10-CM member codes from the CMS ICD-10-CM code set.
Verified current to CMS-HCC V28, payment year 2026 — last reviewed May 30, 2026.