HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Diseases of myoneural junction and muscle (G70-G73)
G70.80
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceLambert-Eaton syndrome, unspecified
Lambert-Eaton syndrome, a rare autoimmune disorder affecting the connection between nerves and muscles, causing muscle weakness that improves with activity.
Buddy Insight
Lambert-Eaton syndrome, unspecified is a rare autoimmune disorder targeting presynaptic voltage-gated calcium channels at the neuromuscular junction, causing proximal muscle weakness that characteristically improves with repeated use.
CMS-HCC V28
MappedHCC 196
RAF 0.402
CMS-HCC V24
MappedHCC 75
RAF 0.425
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 75
RAF 0.0
RXHCC
MappedHCC 153
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
Official- Lambert-Eaton syndrome NOS
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for G70.80 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for G70.80 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for G70.80 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for G70.80 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for G70.80 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for G70.80 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is G70.80 an HCC code?
Yes. G70.80 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre under the CMS-HCC V28 risk adjustment model (and Myasthenia Gravis/Myoneural Conditions and Guillain-Barre Syndrome 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 G70.80
For G70.80to 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 G70.80 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G70.80 is the ICD-10-CM diagnosis code for lambert-eaton syndrome, unspecified. Lambert-Eaton syndrome, a rare autoimmune disorder affecting the connection between nerves and muscles, causing muscle weakness that improves with activity. G70.80 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering diseases of myoneural junction and muscle (g70-g73).
Under the CMS-HCC V28 risk adjustment model, G70.80 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre (HCC 196) with a community, non-dual, aged base RAF weight of 0.402. Under the older CMS-HCC V24 model, G70.80 maps to Myasthenia Gravis/Myoneural Conditions and Guillain-Barre Syndrome (HCC 75) with a community, non-dual, aged base RAF weight of 0.425. 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.
Use this code when Lambert-Eaton syndrome is diagnosed but not associated with another classified disease. Because G70.80 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 G70.80 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code when Lambert-Eaton syndrome is diagnosed but not associated with another classified disease
- •If associated with malignancy or another condition, use G70.81 instead
Clinical Significance
Lambert-Eaton syndrome, unspecified is a rare autoimmune disorder targeting presynaptic voltage-gated calcium channels at the neuromuscular junction, causing proximal muscle weakness that characteristically improves with repeated use. It may be paraneoplastic or autoimmune in nature. Accurate coding is essential as it carries significant HCC value and may prompt cancer screening when paraneoplastic origin is suspected.
Documentation Requirements
- ✓Clinical features: proximal weakness improving with activity, autonomic dysfunction, hyporeflexia
- ✓Electrodiagnostic confirmation: incremental response on repetitive nerve stimulation
- ✓Voltage-gated calcium channel antibody testing results
- ✓Cancer screening results: chest imaging, PET scan to evaluate for small cell lung cancer
- ✓Distinction from myasthenia gravis documented
- ✓Provider's explicit diagnosis of Lambert-Eaton syndrome
Commonly Confused Codes
- •G70.81 — Lambert-Eaton syndrome in disease classified elsewhere should be used when associated with a specific underlying disease
- •G73.1 — Lambert-Eaton syndrome in neoplastic disease should be used when associated with cancer
- •G70.00 — Myasthenia gravis without exacerbation affects postsynaptic receptors and worsens with activity, opposite of Lambert-Eaton syndrome
- •G70.89 — Other specified myoneural disorders is less specific and should not be used when Lambert-Eaton syndrome is diagnosed