G12.24
BillableFamilial motor neuron disease
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G12.24 an HCC code?
Yes. G12.24 maps to Motor Neuron Disease, Including Amyotrophic Lateral Sclerosis under the CMS-HCC V28 risk adjustment model (and Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for G12.24
For G12.24 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed G12.24 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G12.24 is the ICD-10-CM diagnosis code for familial motor neuron disease. A hereditary form of motor neuron disease that runs in families and causes progressive muscle weakness and wasting. G12.24 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering systemic atrophies primarily affecting the central nervous system (g10-g14).
Under the CMS-HCC V28 risk adjustment model, G12.24 maps to Motor Neuron Disease, Including Amyotrophic Lateral Sclerosis (HCC 190) with a community, non-dual, aged base RAF weight of 0.935. Under the older CMS-HCC V24 model, G12.24 maps to Amyotrophic Lateral Sclerosis and Other Motor Neuron Disease (HCC 73) with a community, non-dual, aged base RAF weight of 0.896. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Ensure documentation confirms family history of motor neuron disease to justify this familial classification. Because G12.24 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for G12.24 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation confirms family history of motor neuron disease to justify this familial classification
- •Specify the inheritance pattern (autosomal dominant, recessive, X-linked) if documented
Clinical Significance
Familial motor neuron disease represents inherited forms of motor neuron degeneration, most commonly familial amyotrophic lateral sclerosis caused by mutations in genes such as SOD1, C9orf72, or TARDBP. This diagnosis has implications for genetic counseling of family members and may guide targeted therapies like tofersen for SOD1 mutations.
Documentation Requirements
- ✓Family history of motor neuron disease in first-degree relatives
- ✓Genetic testing results identifying specific mutation if available
- ✓Inheritance pattern documented (autosomal dominant, recessive, X-linked)
- ✓Clinical presentation consistent with motor neuron disease
- ✓Electromyography and nerve conduction study results
- ✓Genetic counseling provided to patient and family members
Commonly Confused Codes
- •G12.21 — Amyotrophic lateral sclerosis: sporadic form without documented familial pattern
- •G12.20 — Motor neuron disease, unspecified: does not capture the familial/genetic component
- •G12.1 — Other inherited spinal muscular atrophy: different disease category affecting anterior horn cells specifically
- •G12.29 — Other motor neuron disease: for non-familial atypical motor neuron diseases