G12.1
Other inherited spinal muscular atrophy
G12.1 (also written G121) is a billable ICD-10-CM diagnosis code for other inherited spinal muscular atrophy. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 11 codes in category G12 (Spinal muscular atrophy and related syndromes). The Alphabetic Index lists it under 11 entries. Its coding notes include 8 Excludes2 entries.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (8 notes)
- 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)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Home Health Primary
Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the Neuro Rehabilitation clinical group.
Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026IRF 60% Rule
On the CMS list of diagnoses used to determine presumptive compliance with the IRF 60 percent rule.
Source: CMS IRF Presumptive Compliance-3, FY 2027 IRF PPS final rule files, effective for discharges on or after October 1, 2026Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 111 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CIPF Primary
IPF MS-DRG adjustment. A principal diagnosis of this code groups to one of these MS-DRGs. Which one depends on other facts of the stay, so the factor is a range:
| MS-DRG | Description | Factor |
|---|---|---|
| 056 | Degenerative nervous system disorders w MCC | 1.12 |
| 057 | Degenerative nervous system disorders w/o MCC | 1.11 |
Inclusion terms
Conditions classified to this code.
- Adult form spinal muscular atrophy
- Childhood form, type II spinal muscular atrophy
- Distal spinal muscular atrophy
- Juvenile form, type III spinal muscular atrophy [Kugelberg-Welander]
- Progressive bulbar palsy of childhood [Fazio-Londe]
- Scapuloperoneal form spinal muscular atrophy
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 11 entries
- Atrophy, atrophic (of), muscle, muscular (diffuse) (general) (idiopathic) (primary), progressive (bulbar), adult
- Atrophy, atrophic (of), muscle, muscular (diffuse) (general) (idiopathic) (primary), progressive (bulbar), spinal, adult
- Atrophy, atrophic (of), muscle, muscular (diffuse) (general) (idiopathic) (primary), spinal, adult form
- Atrophy, atrophic (of), muscle, muscular (diffuse) (general) (idiopathic) (primary), spinal, childhood form, type II
- Atrophy, atrophic (of), muscle, muscular (diffuse) (general) (idiopathic) (primary), spinal, distal
- Atrophy, atrophic (of), muscle, muscular (diffuse) (general) (idiopathic) (primary), spinal, hereditary NEC
- Atrophy, atrophic (of), muscle, muscular (diffuse) (general) (idiopathic) (primary), spinal, juvenile form, type III (Kugelberg- Welander)
- Atrophy, atrophic (of), muscle, muscular (diffuse) (general) (idiopathic) (primary), spinal, scapuloperoneal form
- Fazio-Londe disease or syndrome
- Kugelberg-Welander disease
- Palsy, bulbar (progressive) (chronic), of childhood (Fazio-Londe)