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G10 ICD-10-CM Code: Huntington's disease

G10 maps to CMS-HCC V28 200. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

ICD-10-CM Code View

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Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupG10

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Systemic atrophies primarily affecting the central nervous system (G10-G14)

G10

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Huntington's disease

Huntington's disease is a progressive genetic disorder that causes involuntary movements, emotional problems, and loss of cognitive abilities, typically appearing in middle age.

Buddy the Bee presenting code insight

Buddy Insight

Huntington's disease is a devastating autosomal dominant neurodegenerative disorder with no cure, requiring extensive multidisciplinary care including neurology, psychiatry, rehabilitation, and eventually full-time skilled nursing.

OverviewRisk ModelsCode BookDocumentationAuditNotesEdition comparison

CMS-HCC V28

HCC 200

Coefficient HCC 200: 0.279 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 119

Code-level coefficient reference

ESRD/PACE

HCC 78

Code-level coefficient reference

RXHCC

HCC 160

Code-level coefficient reference

Code Book Path

Official
G1Systemic atrophies primarily affecting the central nervous system (G10-G14)G10Huntington's disease

Inclusion Terms

Official
  • Huntington's chorea
  • Huntington's dementia

Excludes 2

Official
  • certain conditions originating in the perinatal period (P04-P96)Inherited from G00-G99
  • certain infectious and parasitic diseases (A00-B99)Inherited from G00-G99
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from G00-G99
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from G00-G99
  • endocrine, nutritional and metabolic diseases (E00-E88)Inherited from G00-G99
  • injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from G00-G99
  • neoplasms (C00-D49)Inherited from G00-G99
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from G00-G99

Related Codes

Official

No related codes are included in this display for G10. Check the Code Book for the complete code path.

Includes

Official

No Includes notes are included in this display for G10. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for G10. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for G10. Check the code and parent instructions in the Code Book.

Use Additional

Official
  • code, if applicable, to identify:
  • dementia with anxiety (F02.84, F02.A4, F02.B4, F02.C4)
  • dementia with behavioral disturbance (F02.81-, F02.A1-, F02.B1-, F02.C1-)
  • dementia with mood disturbance (F02.83, F02.A3, F02.B3, F02.C3)
  • dementia with psychotic disturbance (F02.82, F02.A2, F02.B2, F02.C2)
  • dementia without behavioral disturbance (F02.80, F02.A0, F02.B0, F02.C0)
  • mild neurocognitive disorder due to known physiological condition (F06.7-)

Code Also

Official

No Code Also instructions are included in this display for G10. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance
Confirmed diagnosis via genetic testing (CAG repeat expansion) or strong clinical criteria
Family history consistent with autosomal dominant inheritance pattern
Age of symptom onset documented
Current stage of disease and functional status

MEAT Support

HCC Buddy guidance
Confirmed diagnosis via genetic testing (CAG repeat expansion) or strong clinical criteria
Family history consistent with autosomal dominant inheritance pattern
Age of symptom onset documented
Current stage of disease and functional status

Audit Caution

HCC Buddy guidance
Failing to code associated manifestations separately (dementia F02.80, depression F06.31, chorea) when documented
Confusing Huntington's chorea with other causes of chorea such as Sydenham's or tardive dyskinesia
Coding Huntington's based on family history alone without confirmed diagnosis in the patient
Not documenting the progressive nature and current disease stage for accurate severity capture

Common Mistakes

HCC Buddy guidance
G25.5 — Other chorea: for chorea from causes other than Huntington's disease
G31.09 — Other frontotemporal dementia: can mimic Huntington's behavioral variant but lacks genetic basis and chorea
G20.A1-G20.C — Parkinson's disease codes: different neurodegenerative process with different movement disorder pattern
F02.80 — Dementia in other diseases: used as additional code for Huntington's dementia manifestation

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is G10 an HCC code?

Yes. G10 (Huntington's disease) maps to HCC 200, Friedreich and Other Hereditary Ataxias; Huntington Disease under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.279. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: G10 is billable and maps to V28 HCC 200, Friedreich and Other Hereditary Ataxias; Huntington Disease. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
G10
Description
Huntington's disease
HCC (V28)
HCC 200 — Friedreich and Other Hereditary Ataxias; Huntington Disease
RAF reference coefficient
0.279
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 200, Friedreich and Other Hereditary Ataxias; Huntington Disease
0.279
ESRDHCC 78, Parkinsons and Huntingtons Diseases
Not separately weighted
RxHCCHCC 160, Huntington Disease
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work G10 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for G10

For G10, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

  • 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

Coder workflow notes

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What This Code Means

G10 is the ICD-10-CM diagnosis code for huntington's disease. Huntington's disease is a progressive genetic disorder that causes involuntary movements, emotional problems, and loss of cognitive abilities, typically appearing in middle age. G10 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering systemic atrophies primarily affecting the central nervous system (g10-g14).

Under the CMS-HCC V28 risk adjustment model, G10 maps to Friedreich and Other Hereditary Ataxias; Huntington Disease (HCC 200) with a source-labeled community, non-dual, aged reference coefficient of 0.279. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Always verify family history documentation and age of onset to support the diagnosis. For G10, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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, source-labeled coefficient references, and MEAT documentation criteria for G10 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Always verify family history documentation and age of onset to support the diagnosis
  • •Code any associated manifestations separately (e.g., dementia, depression, chorea) if they are documented and clinically relevant

Clinical Significance

Huntington's disease is a devastating autosomal dominant neurodegenerative disorder with no cure, requiring extensive multidisciplinary care including neurology, psychiatry, rehabilitation, and eventually full-time skilled nursing. This diagnosis signals very high long-term healthcare costs and resource utilization due to progressive cognitive decline, chorea, and behavioral disturbances.

Documentation Requirements

  • ✓Confirmed diagnosis via genetic testing (CAG repeat expansion) or strong clinical criteria
  • ✓Family history consistent with autosomal dominant inheritance pattern
  • ✓Age of symptom onset documented
  • ✓Current stage of disease and functional status
  • ✓Associated manifestations documented separately (dementia, depression, chorea, dysphagia)
  • ✓Current treatment plan including medications and supportive therapies

Use Additional Code

Commonly Confused Codes

  • •G25.5: Other chorea: for chorea from causes other than Huntington's disease
  • •G31.09: Other frontotemporal dementia: can mimic Huntington's behavioral variant but lacks genetic basis and chorea
  • •G20.A1-G20.C: Parkinson's disease codes: different neurodegenerative process with different movement disorder pattern
  • •F02.80: Dementia in other diseases: used as additional code for Huntington's dementia manifestation

Code Hierarchy

└G10Huntington's disease
└G10Huntington's disease

For G10, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

G10 maps to CMS-HCC V28 category 200, Friedreich and Other Hereditary Ataxias; Huntington Disease. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for G10. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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