G37.5
BillableConcentric sclerosis [Balo] of central nervous system
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G37.5 an HCC code?
Yes. G37.5 maps to Multiple Sclerosis under the CMS-HCC V28 risk adjustment model (and Multiple Sclerosis 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 G37.5
For G37.5 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 G37.5 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G37.5 is the ICD-10-CM diagnosis code for concentric sclerosis [balo] of central nervous system. A rare neurological condition where inflammation and damage to nerve insulation (myelin) occurs in concentric rings in the brain and spinal cord, also known as Balo's disease. G37.5 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering demyelinating diseases of the central nervous system (g35-g37).
Under the CMS-HCC V28 risk adjustment model, G37.5 maps to Multiple Sclerosis (HCC 198) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, G37.5 mapped to the same category but with a base RAF weight of 0.476 — 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.
This is a rare demyelinating disease; ensure diagnosis is confirmed by neuroimaging and clinical presentation before coding. Because G37.5 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 G37.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a rare demyelinating disease; ensure diagnosis is confirmed by neuroimaging and clinical presentation before coding
- •Do not confuse with other demyelinating diseases like multiple sclerosis; documentation should specify 'concentric sclerosis' or 'Balo disease'
Clinical Significance
Concentric sclerosis (Balo disease) is a rare demyelinating disease characterized by concentric rings of alternating demyelinated and myelinated tissue on brain imaging. Originally considered a variant of multiple sclerosis, it is now recognized as a distinct entity with characteristic imaging findings. Accurate identification is important for treatment planning and risk adjustment.
Documentation Requirements
- ✓Documentation specifically identifying concentric sclerosis or Balo disease
- ✓MRI showing characteristic concentric ring or onion-skin pattern of demyelination
- ✓Neurological examination documenting associated deficits
- ✓Clinical timeline documenting disease course
- ✓Evidence distinguishing from multiple sclerosis and other demyelinating conditions
- ✓Current treatment plan (corticosteroids, immunosuppressants)
Commonly Confused Codes
- •G35 — Multiple sclerosis; has focal plaques rather than concentric ring pattern
- •G37.0 — Diffuse sclerosis of CNS (Schilder disease); diffuse rather than concentric pattern
- •G36.9 — Acute disseminated demyelination, unspecified; different imaging and clinical pattern
- •G37.9 — Demyelinating disease of CNS, unspecified; too nonspecific when Balo disease is confirmed
- •G37.81 — MOGAD; different antibody-mediated mechanism