2027 ICD-10-CM Diagnosis Code G12.0Infantile spinal muscular atrophy, type I [Werdnig-Hoffman]
ICD-10-CM Codes›G00–G99›G10-G14›G12
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 190
- Chronic Condition
G12.0 is a billable ICD-10-CM diagnosis code for infantile spinal muscular atrophy, type I [Werdnig-Hoffman]. 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. Coders also document this condition as anterior horn cell disease. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other nervous system disorders (often hereditary or degenerative).
For Medicare Advantage risk adjustment, G12.0 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
Code Classification
Medicare Risk Adjustment (HCC)Billing
G12.0 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.
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.
- Anterior horn cell disease
- Spinal muscular atrophy
- Werdnig-Hoffmann disease
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to G12.0: 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.
- 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.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
Werdnig-Hoffmann G12.0
Syndrome See Also: Disease;
Hoffmann-Werdnig G12.0
Werdnig-Hoffman G12.0
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Werdnig-Hoffmann Disease
the most severe form of spinal muscular atrophy. it is manifested in the first year of life with muscle weakness, poor muscle tone, and lack of motor development. the motor neuron death affects the major organ systems, particularly the respiratory system. most patients die before the age of two secondary to pneumonia.
Patient EducationClinical
Spinal Muscular Atrophy
Spinal muscular atrophy (SMA) is a group of genetic diseases that damages and kills motor neurons. Motor neurons are a type of nerve cell in the spinal cord and lower part of the brain. They control movement in your arms, legs, face, chest, throat, and tongue.
The full article covers:
- What is spinal muscular atrophy (SMA)?
- What are the types of spinal muscular atrophy (SMA) and what are their symptoms?
- What causes spinal muscular atrophy (SMA)?
- How is spinal muscular atrophy (SMA) diagnosed?
- What are the treatments for spinal muscular atrophy (SMA)?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert G12.0 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About G12.0Overview
What is the ICD-10 code for infantile spinal muscular atrophy, type I [Werdnig-Hoffman]?
The ICD-10-CM code for infantile spinal muscular atrophy, type I [Werdnig-Hoffman] is G12.0 (sometimes written as G120). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is G12.0 (Spinal muscular atrophy and related syndromes) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report infantile spinal muscular atrophy, type I [Werdnig-Hoffman] on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does G12.0 group to?
When infantile spinal muscular atrophy, type I [Werdnig-Hoffman] 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 G12.0 a CC or MCC?
CMS lists G12.0 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.
What is the ICD-9 equivalent of G12.0?
Under the General Equivalence Mappings, infantile spinal muscular atrophy, type I [Werdnig-Hoffman] converts to ICD-9-CM 335.0 (werdnig-hoffmann disease). The mapping is a direct match.
What HCC is G12.0?
G12.0 (infantile spinal muscular atrophy, type I [Werdnig-Hoffman]) 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 72 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 155.
Does G12.0 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, G12.0 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.
