G90.3
BillableMulti-system degeneration of the autonomic nervous system
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G90.3 an HCC code?
Yes. G90.3 maps to Parkinson and Huntington Diseases under the CMS-HCC V28 risk adjustment model (and Parkinson's and Huntington's Diseases under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for G90.3
For G90.3 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed G90.3 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G90.3 is the ICD-10-CM diagnosis code for multi-system degeneration of the autonomic nervous system. A progressive neurological disorder where multiple body systems controlled by the autonomic nervous system gradually deteriorate, affecting blood pressure, movement, and other vital functions. G90.3 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering other disorders of the nervous system (g89-g99).
Under the CMS-HCC V28 risk adjustment model, G90.3 maps to Parkinson and Huntington Diseases (HCC 199) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, G90.3 maps to Parkinson's and Huntington's Diseases (HCC 78) with a community, non-dual, aged base RAF weight of 0.584. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Document specific systems affected (cardiovascular, gastrointestinal, etc.) for complete coding. Because G90.3 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G90.3 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document specific systems affected (cardiovascular, gastrointestinal, etc.) for complete coding
- •This is a degenerative condition; note progression and functional decline in documentation
Clinical Significance
Multi-system degeneration of the autonomic nervous system (also known as Shy-Drager syndrome or multiple system atrophy with autonomic predominance) is a progressive neurodegenerative disorder causing severe autonomic failure. This condition carries significant mortality and morbidity, with patients requiring intensive management for orthostatic hypotension, urinary dysfunction, and eventual respiratory compromise. It is a key risk-adjusting diagnosis given the high resource utilization and poor prognosis.
Documentation Requirements
- ✓Clinical findings of progressive autonomic failure (severe orthostatic hypotension, urinary retention/incontinence, anhidrosis)
- ✓Neurological examination documenting cerebellar or parkinsonian features if present
- ✓Imaging or diagnostic workup supporting multi-system atrophy diagnosis
- ✓Functional status assessment and degree of disability
- ✓Current treatment plan addressing autonomic symptoms (e.g., midodrine, fludrocortisone, compression garments)
Excludes 1 — Do NOT code together
- orthostatic hypotension NOS (I95.1)
Commonly Confused Codes
- •G90.1 — Familial dysautonomia: hereditary condition present from birth, not a neurodegenerative process
- •G20 — Parkinson disease: may share parkinsonian features but lacks the prominent autonomic failure component
- •G23.2 — Multiple system atrophy, cerebellar type (MSA-C): when cerebellar ataxia predominates rather than autonomic failure
- •G90.09 — Other idiopathic peripheral autonomic neuropathy: less severe, peripheral autonomic dysfunction without multi-system degeneration