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G31.86 ICD-10-CM Code: Alexander disease

Compare with another code for G31.86Check this code on a claim

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
1 Excludes2 · 7 use-additional codes
Risk adjustment
CMS-HCC V28: 1 category · RxHCC V08 category 112

Billable · FY2027A valid, specific ICD-10-CM code, reportable for dates of service in FY2027.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too; the Instructions section marks which is which.

Use additional codeReport with this code when documented

+3 more in Instructions

Excludes2Not included here; may be reported together

Where it sits Source: CMS/NCHS

Under:Chapter 6: Diseases of the Nervous SystemG30-G32 Other degenerative diseases of the nervous systemG31 Other degenerative diseases of nervous system, not elsewhere classifiedG31.8 Other specified degenerative diseases of nervous system

Most relevant related codes MedCoder-derived

Read off the official notes above and this code’s own position in the tabular list. Which to report is a documentation question; Compare shows the two side by side.

CompareCheck ClaimView Related Codes

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v44, Appendix B.

  • MS-DRG 056 — DEGENERATIVE NERVOUS SYSTEM DISORDERS WITH MCC (MDC 01)
  • MS-DRG 057 — DEGENERATIVE NERVOUS SYSTEM DISORDERS WITHOUT MCC (MDC 01)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 127 — Dementia, Mild or Unspecified

Other models: RxHCC V08 HCC 112

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for G31.86 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

Notes without a marker are published on G31.86 itself; “inherited from” names the category or block whose note applies here.

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from G31

Use Additional Code

Supplementary codes the tabular list directs you to add.

Source: inherited from G31

Coder workflow for G31.86

MedCoder structured workflow — derived from this code’s own official record

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
The conditions the Use Additional Code note names
Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.

Official instructions as workflow

  • Excludes2 — not part of G31.86(1 note)

    Coding workflow: The conditions named in this note are not included in G31.86. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareG93.7

    See the official tabular notes · Guidelines I.A.12.b

  • Use Additional Code — after identifying G31.86(7 notes)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with G31.86 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    ReviewF02.84, F02.A4, F02.B4, F02.C4, F02.81, F02.A1

    See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: A condition the Use Additional Code note names is documented.

Coding question: Is a second code reported with G31.86?

Path: Review the Use Additional Code note and the code it names.

Reason: The additional code is reported when the record documents the condition; a conditional instruction applies only when its condition is met (Guidelines I.A.13).

ReviewF02.84, F02.A4, F02.B4, F02.C4, F02.81, F02.A1

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse G31.86 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of G31.86 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

  • G31.80— Specificity relationship (Review)

    Overlapping diagnoses in the same category.

    Overlapping codes in the same category — the documentation decides which is the more specific fit.

    What moves you there: A record that documents no more than “Leukodystrophy, unspecified” takes G31.80; specificity in the record moves it back here.

    Full comparison: G31.86 vs G31.80 →

  • G93.7— Excludes2 relationship (Informational)

    Distinct conditions — both may be reported.

    A distinct condition — both may be reported when both are documented.

    What moves you there: Documentation of Reye's syndrome adds G93.7; it is not part of this code and both may be reported when both are documented.

    Full comparison: G31.86 vs G93.7 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Code Overview

Alexander disease is a billable ICD-10-CM diagnosis code (G31.86).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder-derived relationships — computed from published CMS and AHRQ datasets

MS-DRG Grouper Relationships (FY2027)

Potential MS-DRG participation — not a DRG assignment.

FY2027 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 2 MS-DRGs: DRG 056 (MDC 01), DRG 057 (MDC 01).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):NVS011 — Neurocognitive disorders (default); NVS006 — Other nervous system disorders (often hereditary or degenerative).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Dementia, Mild or Unspecified) for risk-adjusted payment.

F03.A3 — Unspecified dementia, mild, with mood disturbance, F03.A4 — Unspecified dementia, mild, with anxiety, G30.0 — Alzheimer's disease with early onset, G30.1 — Alzheimer's disease with late onset, G30.8 — Other Alzheimer's disease, G30.9 — Alzheimer's disease, unspecified, G31.01 — Pick's disease, G31.09 — Other frontotemporal neurocognitive disorder, G31.81 — Alpers disease, G31.82 — Leigh's disease, G31.83 — Neurocognitive disorder with Lewy bodies, G91.0 — Communicating hydrocephalus, G91.1 — Obstructive hydrocephalus, G91.2 — (Idiopathic) normal pressure hydrocephalus, G91.3 — Post-traumatic hydrocephalus, unspecified, G91.4 — Hydrocephalus in diseases classified elsewhere, G91.8 — Other hydrocephalus, G91.9 — Hydrocephalus, unspecified, G93.7 — Reye's syndrome, I67.3 — Progressive vascular leukoencephalopathy, +44 more

Related risk categories

These categories interact through CMS's HCC hierarchy — one can suppress the other's risk-adjustment weight when both are present on a claim.

Dementia, Severe, Dementia, Moderate

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical categories (Neurocognitive disorders, Other nervous system disorders (often hereditary or degenerative)).

G31.01 — Pick's disease, G31.09 — Other frontotemporal neurocognitive disorder, G31.1 — Senile degeneration of brain, not elsewhere classified, G31.2 — Degeneration of nervous system due to alcohol, G31.80 — Leukodystrophy, unspecified, G31.81 — Alpers disease, G31.82 — Leigh's disease, G31.83 — Neurocognitive disorder with Lewy bodies, G31.84 — Mild cognitive impairment of uncertain or unknown etiology, G31.85 — Corticobasal degeneration, G31.87 — Primary progressive apraxia of speech, G31.89 — Other specified degenerative diseases of nervous system, G31.9 — Degenerative disease of nervous system, unspecified, G32.0 — Subacute combined degeneration of spinal cord in diseases classified elsewhere, G32.81 — Cerebellar ataxia in diseases classified elsewhere, G32.89 — Other specified degenerative disorders of nervous system in diseases classified elsewhere, G90.01 — Carotid sinus syncope, G90.09 — Other idiopathic peripheral autonomic neuropathy, G90.1 — Familial dysautonomia [Riley-Day], G90.3 — Multi-system degeneration of the autonomic nervous system, +176 more

Contextual Map

Every relationship of G31.86 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Hierarchy

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 127 — Dementia, Mild or Unspecified [CMS-HCC]— CMS-HCC V28 · 2026

MS-DRG Grouper

MDC crossing

  • MDC 01 — Diseases and Disorders of the Nervous System[MDC crossing]: “Diseases and Disorders of the Nervous System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 8,919 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2027

Index entries

  • Disease, diseased, Alexander[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2027

Nearest codes (16)

Change history

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Indexed Clinical Terms (1)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v44 Release, file and checksum · Publisher’s page
Risk adjustment Official source data
2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder-derived relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder editorial explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "G31.86 — Alexander disease." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/g31.86-alexander-disease

Change history

  • FY2024 — October 1, 2023
    Added to the code set
    Alexander disease
    FY2024 changes

Nearest Codes in This Family

Official ICD-10-CM classifications closest to G31.86 in its code family, with their registry titles.

View all codes in the G31 family