2027 ICD-10-CM Diagnosis Code G11.5Hypomyelination - hypogonadotropic hypogonadism - hypodontia

ICD-10-CM Codes›G00–G99›G10-G14›G11

ICD-10-CM G11.5
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G11.5 is a billable ICD-10-CM diagnosis code for hypomyelination - hypogonadotropic hypogonadism - hypodontia. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 58 through 60. 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 170 closely related codes. Coders also document this condition as 4H leukodystrophy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Any dental condition including traumatic injury, Disorders of teeth and gingiva, and Nontraumatic dental conditions.

For Medicare Advantage risk adjustment, G11.5 maps to CMS-HCC Category 200 (Friedreich and Other Hereditary Ataxias; Huntington Disease) under the V28 model, adding a risk factor of about 0.279 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
G11.5
Billable Status
Yes — Valid for Submission
Code Describes
Hypomyelination - hypogonadotropic hypogonadism - hypodontia
Short Description
Hypomyelination - hypogonadotropic hypogonadism - hypodontia
Same as the full description in the CMS dataset.
Parent Code
G11
Hereditary ataxia

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG10-G14Systemic atrophies primarily affecting the central nervous system
CategoryG11Hereditary ataxia
This CodeG11.5Hypomyelination - hypogonadotropic hypogonadism - hypodontia

Medicare Risk Adjustment (HCC)Billing

G11.5 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 200— Friedreich and Other Hereditary Ataxias; Huntington Disease
Payment HCC · PY 2027 one of 17 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.279
community, non-dual, aged · ranges 0.000–0.428 across segments
Hierarchy
Top of its hierarchy
HCC 200 is not superseded by any other condition category
Prior Model (CMS-HCC V24)
HCC 72
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 72 · ESRD (V21): HCC 72 · ESRD (V24): HCC 72
ESRD V21 weights: 0.102 dialysis, 0.256–0.456 functioning graft · ESRD V24 weights: 0.099 dialysis, 0.222–0.523 functioning graft
Part D (RxHCC)
Not mapped
G11.5 does not risk-adjust in the RxHCC prescription drug model

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.

  • 4H leukodystrophy
  • Hypomyelination, hypogonadotropic hypogonadism, hypodontia syndrome

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G11.5: its own notes plus those printed at G11 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.

  • 4H syndrome
  • Pol III-related leukodystrophy

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 G11 Hereditary ataxia applies to 11 codes
  • cerebral palsy (G80.-)
  • hereditary and idiopathic neuropathy (G60.-)
  • metabolic disorders (E70-E88)
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)

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name G11.5, its category, or a range that includes it.

Excludes1 2

These codes carry an Excludes1 note naming G11.5: they are not reported together with it, unless the two conditions are unrelated.

  • R26 Abnormalities of gait and mobility
    hereditary ataxia (G11.-) names G11.-, which includes this code
  • R27 Other lack of coordination
    hereditary ataxia (G11.-) names G11.-, 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 DEN001
Any dental condition including traumatic injury
Default principal diagnosis: inpatient No · outpatient No
CCSR DIG002
Disorders of teeth and gingiva
Default principal diagnosis: inpatient No · outpatient No
CCSR DEN002
Nontraumatic dental conditions
Default principal diagnosis: inpatient No · outpatient No
CCSR NVS006
Other nervous system disorders (often hereditary or degenerative)
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR END013
Pituitary disorders
Default principal diagnosis: inpatient No · outpatient No

Patient EducationClinical

Leukodystrophies

Leukodystrophies are a group of rare genetic disorders that affect the central nervous system (CNS). The CNS is made up of your brain and spinal cord. Leukodystrophies damage the white matter of your CNS. The white matter includes:

The full article covers:

  • What are leukodystrophies?
  • What causes leukodystrophies?
  • What are the symptoms of leukodystrophies?
  • How are leukodystrophies diagnosed?
  • What are the treatments for leukodystrophies?

Read the full article at MedlinePlus

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

Code History & ChangesHistory

Replacement G11.5 replaces the following previously assigned code(s):

  • E23.0 - Hypopituitarism
  • G11.8 - Other hereditary ataxias
  • K00.0 - Anodontia
FY 2024AddedAdded to the ICD-10-CM code setEffective October 1, 2023.
FY 2025–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G11.5Overview

What is the ICD-10 code for hypomyelination - hypogonadotropic hypogonadism - hypodontia?

The ICD-10-CM code for hypomyelination - hypogonadotropic hypogonadism - hypodontia is G11.5 (sometimes written as G115). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G11.5 (Hereditary ataxia) a billable code?

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

What MS-DRG does G11.5 group to?

When hypomyelination - hypogonadotropic hypogonadism - hypodontia is the principal diagnosis on an inpatient stay, it groups to MS-DRG 60, 58, 59, with relative weights from 0.9248 to 1.8430 depending on complications. Higher weights mean higher Medicare reimbursement.

Is G11.5 a CC or MCC?

CMS lists G11.5 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 170 closely related codes in its exclusion list.

What HCC is G11.5?

G11.5 (hypomyelination - hypogonadotropic hypogonadism - hypodontia) maps to CMS-HCC Category 200 (Friedreich and Other Hereditary Ataxias; Huntington Disease), commonly written as HCC 200, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 72 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.

Does G11.5 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, G11.5 adds a risk adjustment factor of about 0.279 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.000 to 0.428 depending on the payment segment). HCC 200 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 200 category page.