2027 ICD-10-CM Diagnosis Code G35.C1Active secondary progressive multiple sclerosis

ICD-10-CM Codes›G00–G99›G35-G37›G35

ICD-10-CM G35.C1
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

G35.C1 is a billable ICD-10-CM diagnosis code for active secondary progressive multiple sclerosis. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Multiple sclerosis.

For Medicare Advantage risk adjustment, G35.C1 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

ICD-10-CM Code
G35.C1
Billable Status
Yes — Valid for Submission
Code Describes
Active secondary progressive multiple sclerosis
Short Description
Active secondary progressive multiple sclerosis
Same as the full description in the CMS dataset.
Parent Code
G35.C
Secondary progressive multiple sclerosis

Code Classification

ChapterG00–G99Diseases of the nervous system
SectionG35-G37Demyelinating diseases of the central nervous system
CategoryG35Multiple sclerosis
This CodeG35.C1Active secondary progressive multiple sclerosis

Medicare Risk Adjustment (HCC)Billing

G35.C1 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.

CMS-HCC V28 Category (Payment Model)
HCC 198— Multiple Sclerosis
Payment HCC · PY 2027 one of 20 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.647
community, non-dual, aged · ranges 0.226–1.143 across segments
Hierarchy
Top of its hierarchy
HCC 198 is not superseded by any other condition category
Prior Model (CMS-HCC V24)
Not mapped under V24
this diagnosis newly risk-adjusts under the V28 model
Other CMS Models
PACE (CMS-HCC V22): HCC 77 · ESRD (V21): HCC 77 · ESRD (V24): HCC 77
ESRD V21 weights: 0.069 dialysis, 0.000–0.546 functioning graft · ESRD V24 weights: 0.111 dialysis, 0.042–1.113 functioning graft
Part D (RxHCC)
RxHCC 159 — Multiple Sclerosis
also risk-adjusts in the Part D prescription drug model (V08)

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.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to G35.C1: 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.

  • Secondary progressive multiple sclerosis with evidence of inflammatory disease activity

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.

From Chapter 6 (G00-G99) Diseases of the nervous system applies to 700 codes
  • 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 G35.C1, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming G35.C1: they are not reported together with it, unless the two conditions are unrelated.

  • G37.3 Acute transverse myelitis in demyelinating disease of central nervous system
    multiple sclerosis (G35-) names G35-, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming G35.C1: its condition is not part of those codes, and both may be reported when the patient has both.

  • G04 Encephalitis, myelitis and encephalomyelitis
    multiple sclerosis (G35-) names G35-, which includes this code

Code First 2

These codes say to code first a condition named in the note, and G35.C1 is one of the conditions named.

  • F02 Dementia in other diseases classified elsewhere
    multiple sclerosis (G35-) names G35-, which includes this code
  • F48.2 Pseudobulbar affect
    multiple sclerosis (G35-) names G35-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR NVS005
Multiple sclerosis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Multiple Sclerosis

    an autoimmune disorder mainly affecting young adults and characterized by destruction of myelin in the central nervous system. pathologic findings include multiple sharply demarcated areas of demyelination throughout the white matter of the central nervous system. clinical manifestations include visual loss, extra-ocular movement disorders, paresthesias, loss of sensation, weakness, dysarthria, spasticity, ataxia, and bladder dysfunction. the usual pattern is one of recurrent attacks followed by partial recovery (see multiple sclerosis, relapsing-remitting), but acute fulminating and chronic progressive forms (see multiple sclerosis, chronic progressive) also occur. (adams et al., principles of neurology, 6th ed, p903)

Patient EducationClinical

Multiple Sclerosis

Multiple sclerosis (MS) is a disease that affects your brain and spinal cord, also called the central nervous system. MS damages myelin, the protective coating around your nerve cells. Myelin helps nerves send messages quickly. When it's damaged, messages between your brain and body slow down or get blocked. This leads to MS symptoms.

The full article covers:

  • What is multiple sclerosis?
  • What are the types of multiple sclerosis?
  • What causes multiple sclerosis?
  • What are the symptoms of multiple sclerosis?
  • How is multiple sclerosis diagnosed?
  • What are the treatments for multiple sclerosis?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code History & ChangesHistory

Replacement G35.C1 replaces the following previously assigned code(s):

  • G35 - Multiple sclerosis
FY 2026AddedAdded to the ICD-10-CM code setEffective October 1, 2025.
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About G35.C1Overview

What is the ICD-10 code for active secondary progressive multiple sclerosis?

The ICD-10-CM code for active secondary progressive multiple sclerosis is G35.C1 (sometimes written as G35C1). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is G35.C1 (Secondary progressive multiple sclerosis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report active secondary progressive multiple sclerosis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does G35.C1 group to?

When active secondary progressive multiple sclerosis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 60, 58, 59, with relative weights from 0.9248 to 1.8430 depending on complications. Higher weights mean higher Medicare reimbursement.

What HCC is G35.C1?

G35.C1 (active secondary progressive multiple sclerosis) 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 also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 159.

Does G35.C1 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, G35.C1 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.