G40.C09
BillableLafora progressive myoclonus epilepsy, not intractable, without status epilepticus
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G40.C09 an HCC code?
Yes. G40.C09 maps to Seizure Disorders and Convulsions under the CMS-HCC V28 risk adjustment model (and Seizure Disorders and Convulsions 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 G40.C09
For G40.C09 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 G40.C09 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G40.C09 is the ICD-10-CM diagnosis code for lafora progressive myoclonus epilepsy, not intractable, without status epilepticus. Lafora disease is a rare, inherited progressive epilepsy causing myoclonic seizures and neurological decline. This code indicates the condition responds to medication and the patient is not currently experiencing prolonged seizure activity. G40.C09 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering episodic and paroxysmal disorders (g40-g47).
Under the CMS-HCC V28 risk adjustment model, G40.C09 maps to Seizure Disorders and Convulsions (HCC 201) with a community, non-dual, aged base RAF weight of 0.262. Under the older V24 model, G40.C09 mapped to the same category but with a base RAF weight of 0.244 — V28 recalibrated weights across the entire model. 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.
Confirm Lafora disease diagnosis through genetic testing or pathological findings in documentation. Because G40.C09 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 G40.C09 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm Lafora disease diagnosis through genetic testing or pathological findings in documentation
- •Verify absence of status epilepticus and that seizures are controlled with current treatment
Clinical Significance
Lafora progressive myoclonus epilepsy, medication-responsive, without status epilepticus likely represents early-stage disease when seizures may still respond to treatment. Lafora disease is a devastating progressive condition that typically presents in late childhood or adolescence and leads to intractable epilepsy, cognitive decline, and death within 10 years of onset. Early-stage medication responsiveness is expected to decline over time.
Documentation Requirements
- ✓Confirmed Lafora disease diagnosis through genetic testing or pathology
- ✓Current seizure control status (responding to medication)
- ✓Absence of status epilepticus
- ✓Disease stage and progression timeline
- ✓Current medication regimen
- ✓Genetic counseling documentation for family members