G31.80 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 Buddy coding tools

ICD-10-CM Code View

HCC Buddy Code Card

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

Code lookupG31.80

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Other degenerative diseases of the nervous system (G30-G32)

G31.80

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

Leukodystrophy, unspecified

A group of inherited disorders affecting the white matter of the brain, causing progressive neurological deterioration without a specific identified type.

Buddy Insight

Leukodystrophy, unspecified, captures a group of rare inherited disorders affecting the white matter of the brain.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 200

Friedreich and Other Heredita...

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

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 119

HHS-HCC 119 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 52

Dementia Without Complication

Code-level coefficient reference

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

G31Other degenerative diseases of nervous system, not elsewhere classified G31.8Other specified degenerative diseases of nervous system G31.80Leukodystrophy, unspecified

Inclusion Terms

Official

No inclusion terms are included in this display for G31.80. Check the code and parent instructions in the Code Book.

Excludes 2

Official

certain conditions originating in the perinatal period (P04-P96)Inherited from G00-G99, G31
certain infectious and parasitic diseases (A00-B99)Inherited from G00-G99, G31
complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from G00-G99, G31
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from G00-G99, G31
endocrine, nutritional and metabolic diseases (E00-E88)Inherited from G00-G99, G31
injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from G00-G99, G31
neoplasms (C00-D49)Inherited from G00-G99, G31
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from G00-G99, G31
Reye's syndrome (G93.7)Inherited from G00-G99, G31

Related Codes

Official

G31.81Alpers disease G31.82Leigh's disease G31.83Neurocognitive disorder with Lewy bodies G31.84Mild cognitive impairment of uncertain or unknown etiology G31.85Corticobasal degeneration

Includes

Official

No Includes notes are included in this display for G31.80. Check the code and parent instructions in the Code Book.

Excludes 1

Official

No Excludes 1 notes are included in this display for G31.80. Check the code and parent instructions in the Code Book.

Code First

Official

No Code First sequencing instructions are included in this display for G31.80. Check the code and parent instructions in the Code Book.

Use Additional

Official

code, if applicable, for codes G31.0-G31.83, G31.85-G31.9, to identify:Inherited from G31
dementia with anxiety (F02.84, F02.A4, F02.B4, F02.C4)Inherited from G31
dementia with behavioral disturbance (F02.81-, F02.A1-, F02.B1-, F02.C1-)Inherited from G31
dementia with mood disturbance (F02.83, F02.A3, F02.B3, F02.C3)Inherited from G31
dementia with psychotic disturbance (F02.82, F02.A2, F02.B2, F02.C2)Inherited from G31
dementia without behavioral disturbance (F02.80, F02.A0, F02.B0, F02.C0)Inherited from G31
mild neurocognitive disorder due to known physiological condition (F06.7-)Inherited from G31

Code Also

Official

No Code Also instructions are included in this display for G31.80. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Documentation confirming leukodystrophy diagnosis via neuroimaging (MRI showing white matter abnormalities)

Genetic testing results if available, even if specific type is not identified

Neurological examination findings documenting motor, cognitive, or developmental deficits

Documentation that specific leukodystrophy subtypes could not be determined

MEAT Support

HCC Buddy guidance

Documentation confirming leukodystrophy diagnosis via neuroimaging (MRI showing white matter abnormalities)

Genetic testing results if available, even if specific type is not identified

Neurological examination findings documenting motor, cognitive, or developmental deficits

Documentation that specific leukodystrophy subtypes could not be determined

Audit Caution

HCC Buddy guidance

Using G31.80 when a specific leukodystrophy type has been identified and has its own ICD-10 code

Confusing inherited leukodystrophies with acquired demyelinating diseases like multiple sclerosis

Not querying for genetic testing results that could identify the specific leukodystrophy subtype

Failing to recognize that some specific leukodystrophies are classified under metabolic codes (E75.x) rather than G31

Common Mistakes

HCC Buddy guidance

G31.86 — Alexander disease; a specific type of leukodystrophy that has its own code

G23.3 — Hypomyelination with atrophy of basal ganglia and cerebellum; specific pattern of white matter disease

G35 — Multiple sclerosis; acquired demyelinating disease, not inherited leukodystrophy

G37.0 — Diffuse sclerosis of central nervous system; different pattern of white matter involvement

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 G31.80 an HCC code?

Yes. G31.80 (Leukodystrophy, unspecified) 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: G31.80 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: G31.80
Description: Leukodystrophy, unspecified
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 52, Dementia Without Complication

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 G31.80 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for G31.80

For G31.80, 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

G31.80 is the ICD-10-CM diagnosis code for leukodystrophy, unspecified. A group of inherited disorders affecting the white matter of the brain, causing progressive neurological deterioration without a specific identified type. G31.80 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering other degenerative diseases of the nervous system (g30-g32).

Under the CMS-HCC V28 risk adjustment model, G31.80 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.

Leukodystrophies are rare genetic disorders; query for specific type if documentation is vague. For G31.80, 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 G31.80 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Leukodystrophies are rare genetic disorders; query for specific type if documentation is vague
•Consider genetic testing documentation and family history when coding these conditions

Clinical Significance

Leukodystrophy, unspecified, captures a group of rare inherited disorders affecting the white matter of the brain. These conditions cause progressive neurological deterioration and require intensive multidisciplinary care. Despite being unspecified, the diagnosis reflects a serious genetic neurological condition with significant care needs and resource utilization.

Documentation Requirements

✓Documentation confirming leukodystrophy diagnosis via neuroimaging (MRI showing white matter abnormalities)
✓Genetic testing results if available, even if specific type is not identified
✓Neurological examination findings documenting motor, cognitive, or developmental deficits
✓Documentation that specific leukodystrophy subtypes could not be determined
✓Family history of neurological disorders if applicable
✓Current treatment plan and specialty referrals

Commonly Confused Codes

•G31.86: Alexander disease; a specific type of leukodystrophy that has its own code
•G23.3: Hypomyelination with atrophy of basal ganglia and cerebellum; specific pattern of white matter disease
•G35: Multiple sclerosis; acquired demyelinating disease, not inherited leukodystrophy
•G37.0: Diffuse sclerosis of central nervous system; different pattern of white matter involvement
•E75.25: Metachromatic leukodystrophy; a specific leukodystrophy with its own code