2026 ICD-10-CM Diagnosis Code G04.31Postinfectious acute necrotizing hemorrhagic encephalopathy

ICD-10-CM Codes›G00–G99›G00-G09›G04

ICD-10-CM G04.31
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

G04.31 is a billable ICD-10-CM diagnosis code for postinfectious acute necrotizing hemorrhagic encephalopathy. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as acute necrotizing encephalopathy of childhood. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Encephalitis.

Code Identity

ICD-10-CM Code
G04.31
Billable Status
Yes — Valid for Submission
Code Describes
Postinfectious acute necrotizing hemorrhagic encephalopathy
Short Description
Postinfectious acute necrotizing hemorrhagic encephalopathy
Same as the full description in the CMS dataset.
Parent Code
G04.3
Acute necrotizing hemorrhagic encephalopathy

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG00-G09Inflammatory diseases of the central nervous system
CategoryG04Encephalitis, myelitis and encephalomyelitis
This CodeG04.31Postinfectious acute necrotizing hemorrhagic encephalopathy

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute necrotizing encephalopathy of childhood

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.

    • Encephalitis(chronic) (hemorrhagic) (idiopathic) (nonepidemic) (spurious) (subacute)
      • acute
        • necrotizing hemorrhagic
          • postinfectious
    • Encephalomyelitis
      • acute necrotizing hemorrhagic
        • postinfectious
    • Encephalopathy(acute)
      • acute necrotizing hemorrhagic
        • postinfectious

Clinical ClassificationClinical

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

CCSR NVS002
Encephalitis
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Encephalitis

Encephalitis is inflammation (swelling) of the brain. It can happen when an infection or medical condition that affects the brain activates your immune system. The inflammation can cause a wide range of symptoms. In extreme cases, it can lead to brain damage, stroke, or even death.

The full article covers:

  • What is encephalitis?
  • What causes encephalitis?
  • Who is more likely to get encephalitis?
  • What are the symptoms of encephalitis?
  • How is encephalitis diagnosed?
  • What are the treatments for encephalitis?
  • Can encephalitis be prevented?

Read the full article at MedlinePlus

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

Convert G04.31 to ICD-9-CMHistory

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

ICD-9-CM
323.62 Postinf encephalitis NEC
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About G04.31Overview

Is G04.31 (Acute necrotizing hemorrhagic encephalopathy) a billable code?

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

What is the ICD-9 equivalent of G04.31?

Under the General Equivalence Mappings, postinfectious acute necrotizing hemorrhagic encephalopathy converts to ICD-9-CM 323.62 (postinf encephalitis NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.