G12.1
BillableOther inherited spinal muscular atrophy
HCC Category Mapping
V28HCC 190 — Motor Neuron Disease, Including Amyotrophic Lateral Sclerosis
0.935V24HCC 72 — Spinal Cord Disorders/Injuries
0.464ESRDHCC 72 — Spinal Cord Disorders/Injuries
0.000RxHCCHCC 155 — Myelitis and Encephalomyelitis
0.000What This Code Means
Inherited forms of spinal muscular atrophy other than the infantile type, causing progressive muscle weakness and wasting.
Coding Tips
- •Differentiate from G12.0 by confirming the patient does not have infantile-onset type I SMA
- •Document the specific type (juvenile, adult-onset, etc.) when available to support medical necessity
Clinical Significance
Other inherited spinal muscular atrophy encompasses types II (intermediate), III (Kugelberg-Welander), and IV (adult-onset), which present later and progress more slowly than type I. These conditions still cause significant disability and drive high costs, particularly with the availability of disease-modifying gene therapies that can cost hundreds of thousands of dollars annually.
Documentation Requirements
- ✓SMN1 gene deletion testing confirming spinal muscular atrophy diagnosis
- ✓Documentation of specific type (II, III, or IV) with age of onset
- ✓Current motor function status (ability to sit, stand, walk)
- ✓Respiratory function assessment
- ✓Disease-modifying therapy if applicable (nusinersen, risdiplam)
- ✓Confirmation that the patient does not have type I infantile form
Commonly Confused Codes
G12.0 — Infantile spinal muscular atrophy type I: most severe form with onset before 6 monthsG12.9 — Spinal muscular atrophy, unspecified: avoid when the inherited type is knownG12.20 — Motor neuron disease, unspecified: different category affecting upper and/or lower motor neuronsG71.0 — Muscular dystrophy: distinct genetic disorder with primary muscle pathology
Code Hierarchy
└G12Spinal muscular atrophy and related syndromes└G12.1Other inherited spinal muscular atrophy
└G12.1Other inherited spinal muscular atrophy