A81.82
BillableGerstmann-Sträussler-Scheinker syndrome
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is A81.82 an HCC code?
Yes. A81.82 maps to Dementia, Mild or Unspecified under the CMS-HCC V28 risk adjustment model.
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 A81.82
For A81.82 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 A81.82 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
A81.82 is the ICD-10-CM diagnosis code for gerstmann-sträussler-scheinker syndrome. Gerstmann-Sträussler-Scheinker syndrome is a rare, inherited brain disease that causes progressive dementia, loss of coordination, and tremors due to abnormal protein buildup in the brain. It is a fatal neurodegenerative condition that typically develops in middle age and progresses over several years. A81.82 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering viral and prion infections of the central nervous system (a80-a89).
Under the CMS-HCC V28 risk adjustment model, A81.82 maps to Dementia, Mild or Unspecified (HCC 127) with a community, non-dual, aged base RAF weight of 0.464. A81.82 was not retained as a payment HCC under the older V24 model, so V28 introduced or recategorized it during the 2024–2026 phase-in. 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.
This is a prion disease requiring documentation of family history and genetic testing confirmation; verify the diagnosis is clearly documented in the medical record before coding. Because A81.82 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 A81.82 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a prion disease requiring documentation of family history and genetic testing confirmation; verify the diagnosis is clearly documented in the medical record before coding
- •Code A81.82 is specific to GSS syndrome; do not confuse with other prion diseases like Creutzfeldt-Jakob disease (A81.0) or fatal familial insomnia (A81.83)
Clinical Significance
Gerstmann-Straussler-Scheinker syndrome is a rare hereditary prion disease caused by PRNP gene mutations, characterized by progressive cerebellar ataxia and later dementia. It has a slower course than CJD (2-10 years survival) and is inherited in an autosomal dominant pattern, making genetic counseling essential.
Documentation Requirements
- ✓Genetic testing confirming PRNP gene mutation (most commonly P102L mutation)
- ✓Family history documenting autosomal dominant inheritance pattern
- ✓Clinical findings: progressive cerebellar ataxia, dysarthria, cognitive decline
- ✓Neuroimaging results showing cerebellar and cerebral atrophy
- ✓Disease stage and functional status documentation
Commonly Confused Codes
- •A81.00 (Creutzfeldt-Jakob disease, unspecified) — CJD typically has a more rapid course with early dementia; GSS presents with cerebellar ataxia predominating over cognitive decline
- •A81.83 (Fatal familial insomnia) — Another hereditary prion disease but with insomnia and autonomic dysfunction as primary features rather than ataxia
- •G11.1 (Early-onset cerebellar ataxia) — Hereditary ataxia without prion pathology; GSS has specific prion protein abnormalities