2027 ICD-10-CM Diagnosis Code G31.81Alpers disease

ICD-10-CM Codes›G00–G99›G30-G32›G31

ICD-10-CM G31.81
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G31.81 is a billable ICD-10-CM diagnosis code for alpers disease. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 56 through 57. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 26 closely related codes. Coders also document this condition as progressive neuronal degeneration of childhood. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neurocognitive disorders and Other nervous system disorders (often hereditary or degenerative).

For Medicare Advantage risk adjustment, G31.81 maps to CMS-HCC Category 127 (Dementia, Mild or Unspecified) under the V28 model, adding a risk factor of about 0.341 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
G31.81
Billable Status
Yes — Valid for Submission
Code Describes
Alpers disease
Short Description
Alpers 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 CodeG31.81Alpers disease

Medicare Risk Adjustment (HCC)Billing

G31.81 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.

CMS-HCC V28 Category (Payment Model)
HCC 127— Dementia, Mild or Unspecified
Payment HCC · PY 2027 one of 65 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.341
community, non-dual, aged · ranges 0.000–0.438 across segments
Hierarchy
Superseded by HCC 125 and HCC 126
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 52
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
ESRD (V21): HCC 52 · ESRD (V24): HCC 52
ESRD V21 weights: 0.045 dialysis, 0.000–0.328 functioning graft · ESRD V24 weights: 0.042 dialysis, 0.000–0.399 functioning graft
Part D (RxHCC)
RxHCC 112 — Dementia, Except Alzheimer's Disease
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Progressive neuronal degeneration of childhood
  • Progressive sclerosing poliodystrophy

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G31.81: its own notes plus those printed at G31 and Chapter 6. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Grey-matter degeneration

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From G31 Other degenerative diseases of nervous system, not elsewhere classified applies to 14 codes
From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From G31 Other degenerative diseases of nervous system, not elsewhere classified applies to 14 codes

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G31.81, its category, or a range that includes it.

Use Additional Code 1

These codes say to use an additional code from the note, and G31.81 is one of the codes named.

  • G31 Other degenerative diseases of nervous system, not elsewhere classified
    code, if applicable, for codes G31.0-G31.83, G31.85-G31.9, to identify: names G31.0-G31.83, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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

  • Alper Syndrome

    a rare genetic syndrome with an autosomal recessive pattern of inheritance. it is caused by a mutation in the gene for the mitochondrial dna polymerase polg. clinical signs are usually not present at birth but develop within the first two years of life and include hypoglycemia from underlying liver dysfunction, failure to thrive, spasticity, myoclonus and seizures. the clinical course follows a progression of neurologic disability and hepatic failure. the prognosis is poor with survival outside the first decade unlikely.

Patient EducationClinical

Degenerative Nerve Diseases

Degenerative nerve diseases affect many of your body's activities, such as balance, movement, talking, breathing, and heart function. Many of these diseases are genetic. Sometimes the cause is a medical condition such as alcoholism, a tumor, or a stroke. Other causes may include toxins, chemicals, and viruses.

Read the full article at MedlinePlus

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

Convert G31.81 to ICD-9-CMHistory

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

ICD-9-CM
330.8 Cereb degen in child 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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G31.81Overview

What is the ICD-10 code for alpers disease?

The ICD-10-CM code for alpers disease is G31.81 (sometimes written as G3181). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G31.81 (Other specified degenerative diseases of nervous system) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report alpers disease on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does G31.81 group to?

When alpers disease is the principal diagnosis on an inpatient stay, it groups to MS-DRG 57, 56, with relative weights from 1.2835 to 2.2649 depending on complications. Higher weights mean higher Medicare reimbursement.

Is G31.81 a CC or MCC?

CMS lists G31.81 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 26 closely related codes in its exclusion list.

Does G31.81 need an additional code?

When the condition applies, yes. The Use Additional Code note at G31, which applies to G31.81, reads: 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); and 1 more listed in the Instructional Notes section. The additional code is reported after G31.81.

What HCC is G31.81?

G31.81 (alpers disease) maps to CMS-HCC Category 127 (Dementia, Mild or Unspecified), commonly written as HCC 127, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 52 under the retired V24 model. It also maps in the ESRD (V21) and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 112.

Does G31.81 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, G31.81 adds a risk adjustment factor of about 0.341 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.000 to 0.438 depending on the payment segment). A more severe related category (HCC 125 and HCC 126) supersedes it when both are reported. See the full factor table on the HCC 127 category page.