2027 ICD-10-CM Diagnosis Code G37.9Demyelinating disease of central nervous system, unspecified
ICD-10-CM Codes›G00–G99›G35-G37›G37
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 198
- Chronic Condition
G37.9 is a billable ICD-10-CM diagnosis code for demyelinating disease of central nervous system, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 58 through 60, 974 through 976. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 166 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other nervous system disorders (neither hereditary nor degenerative).
For Medicare Advantage risk adjustment, G37.9 maps to CMS-HCC Category 198 (Multiple Sclerosis) under the V28 model, adding a risk factor of about 0.647 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
G37.9 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- C11ORF73-related autosomal recessive hypomyelinating leukodystrophy
- Central nervous system demyelinating disease with AIDS
- Central nervous system demyelination due to Whipple disease
- Central nervous system disorder due to Sjögren's syndrome
- Chronic inflammatory demyelinating polyradiculoneuropathy
- Chronic inflammatory demyelinating polyradiculoneuropathy with central nervous system demyelination
- Clinically isolated syndrome
- Demyelinating disease of central nervous system
- Demyelinating disease of central nervous system co-occurrent with human immunodeficiency virus infection
- Demyelination due to systemic vasculitis
- Demyelination of central nervous system co-occurrent and due to mitochondrial disease
- Demyelination of central nervous system co-occurrent and due to neurosarcoidosis
- Demyelination of central nervous system co-occurrent and due to Sjogren disease
- Demyelination of central nervous system co-occurrent and due to systemic lupus erythematosus
- Demyelination of spinal cord
- Epilepsy co-occurrent and due to demyelinating disorder
- Extrapontine myelinolysis
- Hypomyelination of central nervous system structure
- Hypomyelination with brain stem and spinal cord involvement and leg spasticity
- Neurosarcoidosis
- Optic neuritis due to demyelinating disease
- Sjögren's syndrome
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to G37.9: its own notes plus those printed at Chapter 6. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Clinically isolated syndromes
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name G37.9, its category, or a range that includes it.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
Syndrome See Also: Disease;
clinically isolated G37.9
demyelinating G37.9
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Demyelinating Disorder of Central Nervous System
any condition in which there is degeneration of the myelin sheath that covers the nerves of the central nervous system.
Patient EducationClinical
Degenerative Nerve Diseases
Degenerative nerve diseases affect many of your body's activities, such as balance, movement, talking, breathing, and heart function. Many of these diseases are genetic. Sometimes the cause is a medical condition such as alcoholism, a tumor, or a stroke. Other causes may include toxins, chemicals, and viruses.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert G37.9 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About G37.9Overview
What is the ICD-10 code for demyelinating disease of central nervous system, unspecified?
The ICD-10-CM code for demyelinating disease of central nervous system, unspecified is G37.9 (sometimes written as G379). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is G37.9 (Other demyelinating diseases of central nervous system) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report demyelinating disease of central nervous system, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does G37.9 group to?
When demyelinating disease of central nervous system, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 974, 976, 60, 975, 58, 59, with relative weights from 0.7879 to 3.0488 depending on complications. Higher weights mean higher Medicare reimbursement.
Is G37.9 a CC or MCC?
CMS lists G37.9 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 166 closely related codes in its exclusion list.
What is the ICD-9 equivalent of G37.9?
Under the General Equivalence Mappings, demyelinating disease of central nervous system, unspecified converts to ICD-9-CM 341.9 (cns demyelination NOS). The mapping is approximate, so confirm the match fits the documentation.
What HCC is G37.9?
G37.9 (demyelinating disease of central nervous system, unspecified) maps to CMS-HCC Category 198 (Multiple Sclerosis), commonly written as HCC 198, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 77 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does G37.9 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, G37.9 adds a risk adjustment factor of about 0.647 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.226 to 1.143 depending on the payment segment). HCC 198 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 198 category page.
