2027 ICD-10-CM Diagnosis Code G12.21Amyotrophic lateral sclerosis

ICD-10-CM Codes›G00–G99›G10-G14›G12

ICD-10-CM G12.21
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G12.21 is a billable ICD-10-CM diagnosis code for amyotrophic lateral sclerosis. 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 111 closely related codes. The code is restricted by the Medicare Code Editor to adult patients (age 15 through 124). In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other nervous system disorders (often hereditary or degenerative).

For Medicare Advantage risk adjustment, G12.21 maps to CMS-HCC Category 190 (Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease, Spinal Muscular Atrophy) under the V28 model, adding a risk factor of about 1.175 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
G12.21
Billable Status
Yes — Valid for Submission
Code Describes
Amyotrophic lateral sclerosis
Short Description
Amyotrophic lateral sclerosis
Same as the full description in the CMS dataset.
Parent Code
G12.2
Motor neuron disease

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG10-G14Systemic atrophies primarily affecting the central nervous system
CategoryG12Spinal muscular atrophy and related syndromes
This CodeG12.21Amyotrophic lateral sclerosis

Code EditsBilling

Medicare Code Editor checks that affect claim validity for G12.21.

Adult diagnoses
The Medicare Code Editor detects inconsistencies in adult cases by checking a patient's age and any diagnosis on the patient's record. The adult code edits apply to patients age range is 15–124 years inclusive (e.g., senile delirium, mature cataract).

Medicare Risk Adjustment (HCC)Billing

G12.21 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 190— Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease, Spinal Muscular Atrophy
Payment HCC · PY 2027 one of 11 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+1.175
community, non-dual, aged · ranges 0.628–3.642 across segments
Hierarchy
Top of its hierarchy
HCC 190 is not superseded by any other condition category
Prior Model (CMS-HCC V24)
HCC 73
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 73 · ESRD (V21): HCC 73 · ESRD (V24): HCC 73
ESRD V21 weights: 0.117 dialysis, 0.446–1.030 functioning graft · ESRD V24 weights: 0.213 dialysis, 0.739–1.644 functioning graft
Part D (RxHCC)
RxHCC 154 — Amyotrophic Lateral Sclerosis and Other Motor Neuron 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.

  • Amyotrophic lateral sclerosis
  • Amyotrophic lateral sclerosis plus syndrome
  • Amyotrophic lateral sclerosis type 1
  • Amyotrophic lateral sclerosis type 10
  • Amyotrophic lateral sclerosis type 3
  • Amyotrophic lateral sclerosis type 4
  • Amyotrophic lateral sclerosis type 6
  • Amyotrophic lateral sclerosis type 7
  • Amyotrophic lateral sclerosis type 8
  • Amyotrophic lateral sclerosis type 9
  • Amyotrophic lateral sclerosis with autonomic dysfunction
  • Amyotrophic lateral sclerosis with cerebellar dysfunction
  • Amyotrophic lateral sclerosis with dementia
  • Amyotrophic lateral sclerosis with frontotemporal dementia
  • Amyotrophic lateral sclerosis with multiple system atrophy
  • Amyotrophic lateral sclerosis with parkinsonism
  • Amyotrophic lateral sclerosis with spinocerebellar ataxia
  • Amyotrophic lateral sclerosis, parkinsonism, dementia complex
  • Amyotrophic lateral sclerosis, parkinsonism, dementia complex of Kii Peninsula
  • Amyotrophic lateral sclerosis, parkinsonism, dementia complex of West New Guinea
  • Autosomal dominant amyotrophic lateral sclerosis type 1
  • Autosomal recessive amyotrophic lateral sclerosis type 1
  • Juvenile amyotrophic lateral sclerosis
  • Juvenile amyotrophic lateral sclerosis type 2
  • Juvenile amyotrophic lateral sclerosis type 5
  • Multiple system atrophy
  • Restrictive lung disease
  • Restrictive lung disease due to amyotrophic lateral sclerosis

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G12.21: its own notes plus those printed at Chapter 6. A note printed at a category, block or chapter applies to every code under it.

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 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 G12.21, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming G12.21: they are not reported together with it, unless the two conditions are unrelated.

  • M62.5 Muscle wasting and atrophy, not elsewhere classified
    progressive muscular atrophy (G12.21)

Code First 1

These codes say to code first a condition named in the note, and G12.21 is one of the conditions named.

  • F48.2 Pseudobulbar affect
    amyotrophic lateral sclerosis (G12.21)

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 NVS006
Other nervous system disorders (often hereditary or degenerative)
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Amyotrophic Lateral Sclerosis

    a degenerative disorder affecting upper motor neurons in the brain and lower motor neurons in the brain stem and spinal cord. disease onset is usually after the age of 50 and the process is usually fatal within 3 to 6 years. clinical manifestations include progressive weakness, atrophy, fasciculation, hyperreflexia, dysarthria, dysphagia, and eventual paralysis of respiratory function. pathologic features include the replacement of motor neurons with fibrous astrocytes and atrophy of anterior spinal nerve roots and corticospinal tracts. (from adams et al., principles of neurology, 6th ed, pp1089-94)

Patient EducationClinical

Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a nervous system disease that attacks nerve cells called neurons in your brain and spinal cord. These neurons transmit messages from your brain and spinal cord to your voluntary muscles - the ones you can control, like in your arms and legs. At first, this causes mild muscle problems.

Read the full article at MedlinePlus

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

Convert G12.21 to ICD-9-CMHistory

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

ICD-9-CM
335.20 Amyotrophic sclerosis
Approximate The match is approximate rather than exact.
ICD-9-CM
335.21 Prog muscular atrophy
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 G12.21Overview

What is the ICD-10 code for amyotrophic lateral sclerosis?

The ICD-10-CM code for amyotrophic lateral sclerosis is G12.21 (sometimes written as G1221). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G12.21 (Motor neuron disease) a billable code?

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

What MS-DRG does G12.21 group to?

When amyotrophic lateral sclerosis 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 G12.21 a CC or MCC?

CMS lists G12.21 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 111 closely related codes in its exclusion list.

Who can G12.21 be reported for?

The Medicare Code Editor checks amyotrophic lateral sclerosis against patient demographics: this code is intended for adult patients (age 15 through 124). Claims outside these limits are flagged as inconsistent.

What HCC is G12.21?

G12.21 (amyotrophic lateral sclerosis) maps to CMS-HCC Category 190 (Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease, Spinal Muscular Atrophy), commonly written as HCC 190, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 73 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 154.

Does G12.21 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, G12.21 adds a risk adjustment factor of about 1.175 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.628 to 3.642 depending on the payment segment). HCC 190 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 190 category page.