G31.86 – Alexander disease

ICD-10-CM 2027 diagnosis code · Other degenerative diseases of the nervous system

Billable code

ICD-10-CM code G31.86

Code: G31.86 (claims format: G3186)
Description: Alexander disease
Billable: Yes – valid for HIPAA-covered transactions
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 6. Diseases of the nervous system (G00-G99)
Block: G30-G32 Other degenerative diseases of the nervous system
Parent codes: G31 › G31.8

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

G31 – Other degenerative diseases of nervous system, not elsewhere classified

Excludes2 (not included here):

Reye's syndrome (G93.7)

Use additional code:

code, if applicable, for codes G31.0-G31.83, G31.85-G31.9, 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-)

Index terms for G31.86

Entries in the ICD-10-CM alphabetic index that lead to this code:

Disease, diseased, Alexander

Related codes in G31.8

G31.80 – Leukodystrophy, unspecifiedBillable
G31.81 – Alpers diseaseBillable
G31.82 – Leigh's diseaseBillable
G31.83 – Neurocognitive disorder with Lewy bodiesBillable
G31.84 – Mild cognitive impairment of uncertain or unknown etiologyBillable
G31.85 – Corticobasal degenerationBillable
G31.87 – Primary progressive apraxia of speechBillable
G31.89 – Other specified degenerative diseases of nervous systemBillable

Frequently asked questions

What is ICD-10 code G31.86?

G31.86 is the ICD-10-CM code for alexander disease, in the block G30-G32 (Other degenerative diseases of the nervous system).

Is G31.86 a billable code?

Yes. G31.86 is a billable/specific code that can be used to indicate a diagnosis for reimbursement purposes.

What category does G31.86 belong to?

It belongs to category G31 – Other degenerative diseases of nervous system, not elsewhere classified.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.