2026 ICD-10-CM Diagnosis Code G31.86Alexander disease

ICD-10-CM Codes›G00–G99›G30-G32›G31

ICD-10-CM G31.86
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G31.86 is a billable ICD-10-CM diagnosis code for alexander disease. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neurocognitive disorders and Other nervous system disorders (often hereditary or degenerative).

Code Identity

ICD-10-CM Code
G31.86
Billable Status
Yes — Valid for Submission
Code Describes
Alexander disease
Short Description
Alexander disease
Same as the full description in the CMS dataset.
Parent Code
G31.8
Other specified degenerative diseases of nervous system

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG30-G32Other degenerative diseases of the nervous system
CategoryG31Other degenerative diseases of nervous system, not elsewhere classified
This CodeG31.86Alexander disease

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Alexander disease
  • Alexander disease type I
  • Alexander disease type II

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Disease, diseased
      • Alexander

Clinical ClassificationClinical

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

CCSR NVS011
Neurocognitive disorders
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR NVS006
Other nervous system disorders (often hereditary or degenerative)
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Alexander Disease

    rare leukoencephalopathy with infantile-onset accumulation of rosenthal fibers in the subpial, periventricular, and subependymal zones of the brain. rosenthal fibers are glial fibrillary acidic protein aggregates found in astrocytes. juvenile- and adult-onset types show progressive atrophy of the lower brainstem instead. de novo mutations in the gfap gene are associated with the disease with propensity for paternal inheritance.

  • Alexander Disease

    a rare genetic neurodegenerative disorder which belongs to the group of leukodystrophies. it has a slow and progressive clinical course and is characterized by developmental delay, macrocephaly, seizures, dementia and spasticity.

Code History & ChangesHistory

Replacement G31.86 replaces the following previously assigned code(s):

  • G31.89 - Other specified degenerative diseases of nervous system
FY 2024AddedAdded to the ICD-10-CM code setEffective October 1, 2023.
FY 2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About G31.86Overview

Is G31.86 (Other specified degenerative diseases of nervous system) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report alexander disease on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.