What is ICD-10 code G90.B?

G90.B is the ICD-10-CM diagnosis code for LMNB1-related autosomal dominant leukodystrophy. LMNB1-related autosomal dominant leukodystrophy is a rare genetic disorder affecting the white matter of the brain, caused by mutations in the LMNB1 gene. It belongs to the ICD-10-CM chapter for diseases of the nervous system (g00-g99). G90.B is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. G90.B is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. G90.B is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. G90.B is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for G90.B?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. G90.B is a payment HCC under V28 (Cerebellar Ataxia and Other Degenerative Diseases of Nervous System) but was not retained as a payment HCC under V24. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting G90.B?

Genetic testing confirmation should be documented in the medical record This is a rare disease; ensure genetic counseling and specialized neurology involvement is documented Because G90.B maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

G90.B ICD-10 Code: LMNB1-related autosomal

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupG90.BEffective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the nervous system (G00-G99) / Other disorders of the nervous system (G89-G99)

G90.B

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

LMNB1-related autosomal dominant leukodystrophy

LMNB1-related autosomal dominant leukodystrophy is a rare genetic disorder affecting the white matter of the brain, caused by mutations in the LMNB1 gene.

Buddy Insight

LMNB1-related autosomal dominant leukodystrophy is a rare inherited white matter disease caused by duplication of the LMNB1 gene, leading to progressive demyelination of the central nervous system.

CMS-HCC V28

Mapped

HCC 200

Cerebellar Ataxia and Other D...

RAF 0.262

CMS-HCC V24

Not risk-adjusted for this model/period.

RAF 0

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Not risk-adjusted for this model/period.

RAF 0

RXHCC

Not risk-adjusted for this model/period.

RAF 0

Code Trumping

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Code Book Path

Official

G90Disorders of autonomic nervous system

G90.BLMNB1-related autosomal dominant leukodystrophy

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for G90.B in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for G90.B in this effective period.

Related Child Codes

Official

G90.0Idiopathic peripheral autonomic neuropathy

G90.1Familial dysautonomia [Riley-Day]

G90.2Horner's syndrome

G90.3Multi-system degeneration of the autonomic nervous system

G90.4Autonomic dysreflexia

Includes

Official

ICD-10-CM does not list Includes notes for G90.B in this effective period.

Excludes 1

Official

dysfunction of the autonomic nervous system due to alcohol (G31.2)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for G90.B in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for G90.B in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for G90.B in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Genetic testing confirming LMNB1 gene duplication

MRI findings demonstrating progressive white matter changes consistent with leukodystrophy

Neurological examination documenting pyramidal signs, cerebellar dysfunction, and autonomic abnormalities

Family history of autosomal dominant inheritance pattern

MEAT Support

HCC Buddy guidance

Genetic testing confirming LMNB1 gene duplication

MRI findings demonstrating progressive white matter changes consistent with leukodystrophy

Neurological examination documenting pyramidal signs, cerebellar dysfunction, and autonomic abnormalities

Family history of autosomal dominant inheritance pattern

Audit Caution

HCC Buddy guidance

Using a nonspecific leukodystrophy or white matter disease code when the LMNB1 genetic confirmation exists

Confusing with other adult-onset leukodystrophies that have their own specific codes

Failing to document the genetic confirmation which is required to justify this specific code

Not coding associated manifestations (autonomic dysfunction, cerebellar ataxia) separately

Common Mistakes

HCC Buddy guidance

G93.44 — Adult-onset leukodystrophy with axonal spheroids: different genetic basis (CSF1R gene), different pathology

G93.42 — Megalencephalic leukoencephalopathy with subcortical cysts: typically childhood onset, different genetic cause

G35 — Multiple sclerosis: acquired demyelinating disease with relapsing-remitting pattern, not hereditary

E75.25 — Metachromatic leukodystrophy: different enzyme deficiency (arylsulfatase A), different inheritance pattern

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 G90.B an HCC code?

Yes. G90.B maps to Cerebellar Ataxia and Other Degenerative Diseases of Nervous System under the CMS-HCC V28 risk adjustment model.

HCC Category Mapping

V28HCC 200, Cerebellar Ataxia and Other Degenerative Diseases of Nervous System

0.262

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 G90.B

For G90.Bto 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 G90.B during that encounter, not just copy-forwarded from a problem list.

What This Code Means

G90.B is the ICD-10-CM diagnosis code for lmnb1-related autosomal dominant leukodystrophy. LMNB1-related autosomal dominant leukodystrophy is a rare genetic disorder affecting the white matter of the brain, caused by mutations in the LMNB1 gene. G90.B sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering other disorders of the nervous system (g89-g99).

Under the CMS-HCC V28 risk adjustment model, G90.B maps to Cerebellar Ataxia and Other Degenerative Diseases of Nervous System (HCC 200) with a community, non-dual, aged base RAF weight of 0.262. G90.B was not retained as a payment HCC under the older V24 model, so V28 introduced or recategorized it during the 2024–2026 phase-in. 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.

Genetic testing confirmation should be documented in the medical record. Because G90.B 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 G90.B sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Genetic testing confirmation should be documented in the medical record
•This is a rare disease; ensure genetic counseling and specialized neurology involvement is documented

Clinical Significance

LMNB1-related autosomal dominant leukodystrophy is a rare inherited white matter disease caused by duplication of the LMNB1 gene, leading to progressive demyelination of the central nervous system. It typically presents in the fourth or fifth decade of life with autonomic dysfunction, cerebellar ataxia, and pyramidal signs. This is a significant risk adjustment code given the progressive neurological deterioration and high care needs.

Documentation Requirements

✓Genetic testing confirming LMNB1 gene duplication
✓MRI findings demonstrating progressive white matter changes consistent with leukodystrophy
✓Neurological examination documenting pyramidal signs, cerebellar dysfunction, and autonomic abnormalities
✓Family history of autosomal dominant inheritance pattern
✓Current functional status and neurological progression documentation

Commonly Confused Codes

•G93.44: Adult-onset leukodystrophy with axonal spheroids: different genetic basis (CSF1R gene), different pathology
•G93.42: Megalencephalic leukoencephalopathy with subcortical cysts: typically childhood onset, different genetic cause
•G35: Multiple sclerosis: acquired demyelinating disease with relapsing-remitting pattern, not hereditary
•E75.25: Metachromatic leukodystrophy: different enzyme deficiency (arylsulfatase A), different inheritance pattern