2027 ICD-10-CM Diagnosis Code G10Huntington's disease

ICD-10-CM Codes›G00–G99›G10-G14›G10

ICD-10-CM G10
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G10 is a billable ICD-10-CM diagnosis code for Huntington's disease. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 56 through 57. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 67 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other nervous system disorders (often hereditary or degenerative).

For Medicare Advantage risk adjustment, G10 maps to CMS-HCC Category 200 (Friedreich and Other Hereditary Ataxias; Huntington Disease) under the V28 model, adding a risk factor of about 0.279 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
G10
Billable Status
Yes — Valid for Submission
Code Describes
Huntington's disease
Short Description
Huntington's disease
Same as the full description in the CMS dataset.
Chapter
G10-G14
Systemic atrophies primarily affecting the central nervous system

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG10-G14Systemic atrophies primarily affecting the central nervous system
CategoryG10Huntington's disease
This CodeG10Huntington's disease

Medicare Risk Adjustment (HCC)Billing

G10 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.

CMS-HCC V28 Category (Payment Model)
HCC 200— Friedreich and Other Hereditary Ataxias; Huntington Disease
Payment HCC · PY 2027 one of 17 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.279
community, non-dual, aged · ranges 0.000–0.428 across segments
Hierarchy
Top of its hierarchy
HCC 200 is not superseded by any other condition category
Prior Model (CMS-HCC V24)
HCC 78
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 78 · ESRD (V21): HCC 78 · ESRD (V24): HCC 78
ESRD V21 weights: 0.065 dialysis, 0.141–0.583 functioning graft · ESRD V24 weights: 0.079 dialysis, 0.206–0.608 functioning graft
Part D (RxHCC)
RxHCC 160 — Huntington Disease
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Akinetic-rigid form of Huntington's disease
  • Altered behavior in Huntington's dementia
  • Atrophy of caudate nucleus
  • Chorea co-occurrent and due to Huntington disease-like condition
  • Dementia due to genetic disease
  • Dementia due to Huntington chorea
  • Huntington disease-like 2
  • Huntington disease-like syndrome
  • Huntington's chorea
  • Juvenile onset Huntington's disease
  • Late onset Huntington's disease
  • Progressive chorea
  • Structural abnormality of caudate nucleus

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G10: its own notes plus those printed at Chapter 6. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Huntington's chorea
  • Huntington's dementia

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G10, its category, or a range that includes it.

Excludes1 3

These codes carry an Excludes1 note naming G10: they are not reported together with it, unless the two conditions are unrelated.

  • G21 Secondary parkinsonism
    Huntington's disease (G10)
  • G25.5 Other chorea
    Huntington's chorea (G10)
  • I02 Rheumatic chorea
    Huntington's chorea (G10)

Code First 2

These codes say to code first a condition named in the note, and G10 is one of the conditions named.

  • F02 Dementia in other diseases classified elsewhere
    Huntington's disease (G10)
  • F06.7 Mild neurocognitive disorder due to known physiological condition
    Huntington's disease (G10)

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NVS006
Other nervous system disorders (often hereditary or degenerative)
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Huntington Disease

    a familial disorder inherited as an autosomal dominant trait and characterized by the onset of progressive chorea and dementia in the fourth or fifth decade of life. common initial manifestations include paranoia; poor impulse control; depression; hallucinations; and delusions. eventually intellectual impairment; loss of fine motor control; athetosis; and diffuse chorea involving axial and limb musculature develops, leading to a vegetative state within 10-15 years of disease onset. the juvenile variant has a more fulminant course including seizures; ataxia; dementia; and chorea. (from adams et al., principles of neurology, 6th ed, pp1060-4)

Patient EducationClinical

Huntington's Disease

Huntington's disease (HD) is an inherited disease that causes certain nerve cells in the brain to waste away. People are born with the defective gene, but symptoms usually don't appear until middle age. Early symptoms of HD may include uncontrolled movements, clumsiness, and balance problems.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert G10 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
333.4 Huntington's chorea
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G10Overview

What is the ICD-10 code for Huntington's disease?

The ICD-10-CM code for Huntington's disease is G10. It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G10 (Huntington's disease) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Huntington's disease on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does G10 group to?

When Huntington's disease is the principal diagnosis on an inpatient stay, it groups to MS-DRG 57, 56, with relative weights from 1.2835 to 2.2649 depending on complications. Higher weights mean higher Medicare reimbursement.

Is G10 a CC or MCC?

CMS lists G10 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 67 closely related codes in its exclusion list.

Does G10 need an additional code?

When the condition applies, yes. The Use Additional Code note reads: 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); and 1 more listed in the Instructional Notes section. The additional code is reported after G10.

What HCC is G10?

G10 (Huntington's disease) maps to CMS-HCC Category 200 (Friedreich and Other Hereditary Ataxias; Huntington Disease), commonly written as HCC 200, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 78 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 160.

Does G10 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, G10 adds a risk adjustment factor of about 0.279 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.000 to 0.428 depending on the payment segment). HCC 200 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 200 category page.