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G35.C0

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🧬 ICD-10 CM G35.C0 — Primary Progressive Multiple Sclerosis without Acute Exacerbation

Billable Code Confirmed

ICD-10 CM G35.C0 is a valid, billable 5-character ICD-10-CM code for FY2026. All required characters are present: G35 (category) + .C (primary progressive phenotype) + 0 (without acute exacerbation).

Non-Billable Parent Codes — Never Submit These

  • ❌ G35 — 3-character header — missing phenotype and exacerbation status
  • ❌ G35.C — 4-character header — missing exacerbation status

Always submit G35.C0 (all 5 characters) when PPMS is documented at its baseline progression.

Clinical Context: "Primary Progressive" vs. Other Phenotypes

ICD-10 CM G35.C0 specifically identifies Primary Progressive Multiple Sclerosis (PPMS). Unlike Relapsing-Remitting MS (RRMS), which features distinct attacks followed by recovery, PPMS is characterized by a gradual, continuous accumulation of neurologic disability from symptom onset. The 0 indicates the patient is without an acute exacerbation—meaning they are currently experiencing their baseline, steady progression rather than a sudden, rapid inflammatory flare.

Code Classification

ICD-10-CM Diagnosis Code — Fields for wRVU, assistant payable, and global period are not applicable. For associated inpatient profee and facility procedure coding, see the CPT Procedural Crosswalk and ICD-10-PCS Crosswalk sections below.

🔍 Code Description

ICD-10 CM G35.C0 classifies Primary progressive multiple sclerosis without acute exacerbation. It denotes an immune-mediated demyelinating disease of the central nervous system where the clinical course is marked by steady functional decline from the very beginning.

In PPMS, the autoimmune attack on the myelin sheath and the underlying nerve fibers (axons) leads to less prominent inflammatory “plaques” in the brain compared to RRMS, but often a higher burden of lesions in the spinal cord. This results in progressive spinal cord atrophy and the hallmark symptom of gradually worsening lower extremity weakness and spasticity.

The qualifier “without acute exacerbation” (also known as a relapse or flare) means the patient is not currently suffering from a rapid, acute onset of new neurological symptoms (or severe worsening of old ones) that typically require high-dose intravenous corticosteroid intervention.

🌳 Code Tree / Hierarchy


G35 Multiple Sclerosis ❌ Non-billable

│
├── G35.A Multiple sclerosis, unspecified ✅ Billable
├── G35.B Relapsing-remitting multiple sclerosis (RRMS) ❌ Non-billable
│ │
│ ├── G35.B0 RRMS without acute exacerbation ✅ Billable
│ └── G35.B1 RRMS with acute exacerbation ✅ Billable
│
├── G35.C Primary progressive multiple sclerosis (PPMS) ❌ Non-billable
│ │
│ ├── G35.C0 PPMS WITHOUT ACUTE EXACERBATION ◀ THIS CODE ✅ Billable
│ └── G35.C1 PPMS with acute exacerbation ✅ Billable
│
├── G35.D Secondary progressive multiple sclerosis (SPMS) ❌ Non-billable
│ │
│ ├── G35.D0 SPMS without acute exacerbation ✅ Billable
│ └── G35.D1 SPMS with acute exacerbation ✅ Billable
│
└── G35.E Clinically isolated syndrome (CIS) ✅ Billable

Specificity is Key for Proper Care Management

PPMS represents only about 10-15% of all MS cases. Treatment protocols are vastly different. While dozens of Disease-Modifying Therapies (DMTs) exist for RRMS, very few (such as Ocrelizumab) are FDA-approved for PPMS. Capturing G35.C0 justifies the medical necessity for these specific, high-cost biologic therapies.

✅ Includes

The following clinical terms and scenarios map to G35.C0 when acute flare is absent:

  • Primary progressive MS (PPMS) NOS
  • Chronic progressive multiple sclerosis
  • Progressive multiple sclerosis from onset

❌ Excludes

Excludes 1 — Cannot Be Coded Simultaneously with G35.C0

CodeDescriptionNote
G36.0Neuromyelitis optica [Devic]Mutually exclusive — NMO involves antibodies targeting aquaporin-4 (AQP4); pathophysiology is distinct from MS. Code G36.0 instead if NMO is confirmed.
G36.9Acute disseminated demyelinationADEM is typically a monophasic post-infectious process, unlike the chronic, progressive nature of PPMS.
G37.81MOGADMyelin oligodendrocyte glycoprotein antibody-associated disease is a distinct demyelinating syndrome.

Excludes 1 Violation Risk

You cannot assign MS codes concurrently with other specified central demyelinating diseases like NMO or MOGAD. If a patient’s diagnosis is revised from MS to NMO based on autoantibody testing, use the NMO code exclusively.

Excludes 2 — May Be Coded in Addition if Separately Present

CodeDescriptionNote
G37.-Other demyelinating diseases of central nervous systemMay be coded additionally if a completely distinct condition is present.

📋 Clinical Overview

Phenotype Distinction — The Critical Factor

The MS category expansion requires coders to distinguish the disease trajectory. This distinction must be explicitly documented by the neurologist.

FeaturePrimary Progressive (PPMS)Relapsing-Remitting (RRMS)Secondary Progressive (SPMS)
Disease CourseSteady decline from onset.Unpredictable attacks followed by periods of remission.Initial relapsing course that shifts to steady progression.
Typical OnsetUsually older (age 40+), equal male-to-female ratio.Usually younger (age 20-30), highly female-predominant.Usually diagnosed 10-20 years after RRMS onset.
Common PresentationProgressive myelopathy (spinal cord involvement), gait issues.Optic neuritis, sensory changes, focal brainstem signs.Gradually worsening mobility despite lack of obvious flares.
Code FamilyG35.C- series (This code)G35.B- seriesG35.D- series

CDI Query Trigger — "Multiple Sclerosis" NOS

If the physician documents only “Multiple Sclerosis” for a patient clearly on a DMT or with a long history of the disease, a CDI query is warranted. The difference between RRMS, PPMS, and SPMS dictates risk adjustment, care pathways, and payer approvals. Defaulting to G35.A (Unspecified) should be a last resort.

Manifestations & Symptom Burden

Unlike an acute exacerbation, the symptoms of G35.C0 represent the patient’s continuous baseline. These often include:

  • Progressive spastic paraparesis: Stiffness and weakness in the legs.
  • Neurogenic bowel/bladder: Urgency, retention, or incontinence.
  • Cognitive changes: Processing speed delays.
  • Severe fatigue: Often disproportionate to the physical exertion.

Coding Manifestations

Always code the documented manifestations to fully capture the patient’s complexity, especially in the inpatient profee setting where evaluation and management of these specific symptoms drive the E/M level. Examples include:

  • R27.0 — Ataxia, unspecified
  • M62.838 — Other muscle spasm
  • N31.9 — Neuromuscular dysfunction of bladder, unspecified
  • R53.83 — Other fatigue
  • Z99.3 — Dependence on wheelchair

💰 HCC Risk Adjustment (CMS-HCC v28)

FieldDetail
CMS-HCC Model Versionv28 (2024-2025 Implementation)
HCC Assignment✅ Mapped
HCC CategoryHCC 77 — Multiple Sclerosis
RAF Coefficient~0.45 - 0.65 (varies by demographic/status)

G35.C0 maps directly to an HCC and contributes significantly to the RAF score.

Capture Annually

Even though PPMS is a lifelong, incurable condition, it must be evaluated, documented, and coded at least once every calendar year to be calculated in the patient’s risk profile.

🏥 MS-DRG Assignment

MDC 01 — Diseases and Disorders of the Nervous System

DRGTitleEst. Relative Weight*
DRG 058Multiple Sclerosis & Cerebellar Ataxia with MCC~1.30 - 1.50
DRG 059Multiple Sclerosis & Cerebellar Ataxia with CC~0.90 - 1.10
DRG 060Multiple Sclerosis & Cerebellar Ataxia without CC/MCC~0.65 - 0.80

Approximate. Verify against IPPS FY2026 Final Rule tables.

MS as a Secondary Diagnosis

While an admission strictly for PPMS without exacerbation is rare, PPMS patients are frequently admitted for complications (e.g., severe pressure ulcers, urosepsis, aspiration pneumonia). When G35.C0 is a secondary diagnosis, it often functions as a crucial Comorbidity (CC) that accurately increases the DRG weight to reflect the intensive nursing and physical therapy requirements.

🔗 Related ICD-10-CM Codes

Exacerbation Status Variants

CodeDescription
G35.C0PPMS without acute exacerbation ← This Code
G35.C1PPMS with acute exacerbation

Phenotype Variants

CodeDescription
G35.B0Relapsing-remitting multiple sclerosis without acute exacerbation
G35.D0Secondary progressive multiple sclerosis without acute exacerbation
G35.AMultiple sclerosis, unspecified

🛠️ Commonly Associated CPT Codes (Neurology / PM&R)

Outpatient and Profee Setting Context

The CPT codes below are associated with the diagnostic workup and management of PPMS in profee and outpatient settings.

CPT CodeDescriptionProfee Coding Notes (Modifier 26)
70551MRI brain without contrast materialAppend -26 if the physician is only interpreting the imaging in a facility setting.
72141MRI cervical spine without contrastPPMS often has a heavy cervical cord lesion burden.
62270Spinal puncture, lumbar, diagnosticUsed to check for oligoclonal bands.
96365Intravenous infusion, for therapy, prophylaxis, or diagnosis; initial, up to 1 hourFrequently used for administering DMTs like Ocrelizumab.
96366Intravenous infusion, each additional hour

NCCI Bundling Considerations

  • When coding 62270 (lumbar puncture), fluoroscopic guidance (77003) is typically bundled depending on the payer, but may be billed separately with appropriate modifiers if distinct medical necessity is documented.
  • Infusion services (96365) billed on the same day as an E/M visit require the E/M to be significant and separately identifiable (Modifier -25).

🔬 ICD-10-PCS Crosswalk (Inpatient Procedures)

When G35.C0 is an inpatient diagnosis and a procedure is performed (e.g., during an admission for severe disease progression requiring inpatient rehab transfer or complication management), these PCS codes are relevant.

PCS SectionBody SystemRoot OperationClinical Application
3 (Administration)E (Physiological Systems)0 (Introduction)Infusion of Disease-Modifying Therapy (e.g., Ocrelizumab). Example: 3E033GC (Intro of Other Therapeutic Sub into Peripheral Vein).
0 (Medical & Surgical)0 (Central Nervous System)9 (Drainage)Diagnostic Lumbar Puncture. Example: 009U3ZX (Drainage of Spinal Canal, Percutaneous, Diagnostic).
0 (Medical & Surgical)0 (Central Nervous System)H (Insertion)Implantation of intrathecal baclofen pump for severe, refractory spasticity associated with PPMS.

💊 Coding Scenarios and Examples

Scenario 1 — Outpatient Biologic Infusion (Profee / Outpatient Facility)

Clinical Vignette: A 52-year-old male with a 5-year history of primary progressive MS presents to the outpatient infusion center for his scheduled half-dose of Ocrevus (ocrelizumab). Neurologist’s note states the patient’s gait continues to slowly decline, but there are no signs of an acute flare. Infusion lasts exactly 2.5 hours without complication.

CPT / HCPCS (Profee/Outpatient):

  • 96365 — IV infusion, initial, up to 1 hour
  • 96366 x2 — IV infusion, each additional hour
  • J9296 — Injection, ocrelizumab, 1 mg (Code units based on exact dosage)

ICD-10-CM:

  • G35.C0 — Primary progressive multiple sclerosis without acute exacerbation
  • R26.89 — Other abnormalities of gait and mobility (Supports the clinical picture of slow decline)

Scenario 2 — Admitted for Sepsis, PPMS as Comorbidity (Inpatient Facility)

Clinical Vignette: A 60-year-old female with advanced PPMS (wheelchair dependent, neurogenic bladder managed with indwelling Foley) is admitted from the ER for altered mental status and hypotension. Blood cultures and urine cultures are positive for E. coli. She is treated with IV antibiotics for severe sepsis. Her MS is noted to be at baseline.

Principal Diagnosis:

  • A41.51 — Sepsis due to Escherichia coli (Reason for admission)

Secondary Diagnoses:

  • N39.0 — Urinary tract infection, site not specified
  • G35.C0 — Primary progressive multiple sclerosis without acute exacerbation (Crucial secondary diagnosis driving nursing care burden)
  • N31.9 — Neuromuscular dysfunction of bladder, unspecified
  • Z99.3 — Dependence on wheelchair
  • Z46.6 — Encounter for fitting and adjustment of urinary device (Foley catheter)

MS-DRG Assignment: - The sepsis principal diagnosis groups this to MDC 18. The inclusion of G35.C0 and other complexities acts as a CC, properly adjusting the DRG weight (e.g., DRG 871 - Septicemia or Severe Sepsis w/o MV >96 Hours w/ MCC, if an MCC is present, or DRG 872 w/ CC).

Scenario 3 — CDI Query: Clarifying the Disease Course

Clinical Vignette: The H&P for a patient admitted to the inpatient rehab unit states: “Patient has a long history of multiple sclerosis, worsening lower extremity weakness over the last 3 years without distinct attacks. Admitted for intensive physical therapy and baclofen pump optimization.”

Action / Outcome: If a coder relies solely on the term “multiple sclerosis,” they would assign G35.A (Unspecified). However, the clinical description (“worsening… without distinct attacks”) strongly points to a progressive phenotype. A CDI query should be sent to the attending physician to clarify the exact phenotype.

Query Response: The physician updates the documentation to “Primary Progressive MS.”

Corrected ICD-10-CM Coding:

  • G35.C0 — Primary progressive multiple sclerosis without acute exacerbation
  • Z51.89 — Encounter for other specified aftercare (Baclofen pump optimization)

⚠️ Coding Pitfalls and Tips

Pitfall or Tip
❌Do not default to G35.A (Unspecified) if documentation provides clues. If the note says “PPMS,” “SPMS,” or “RRMS,” you must use the specific 4th/5th character.
❌Do not use G35.C1 (with exacerbation) unless explicitly stated. An “exacerbation” in MS is a distinct, acute inflammatory event. A patient saying they feel “a bit worse” or the natural slow decline of PPMS does not constitute an acute exacerbation.
✅Sequence properly. In an inpatient setting, if the patient is admitted for an acute issue (e.g., pneumonia, UTI, fracture), code the acute condition first. G35.C0 is sequenced secondarily but remains critical for DRG capture and risk adjustment.
✅Capture all manifestations. For profee coders, capturing the specific manifestations (spasticity, neurogenic bladder, fatigue) paints a clear picture of the Medical Decision Making (MDM) complexity, supporting higher level E/M codes.
✅Append Modifier -26 correctly. If billing profee for diagnostic testing (MRIs, OCTs) performed in a hospital setting, ensure Modifier -26 is appended so you are only billing for the professional interpretation.

📚 Sources

  1. CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2026. 2. National Multiple Sclerosis Society. Types of MS: Primary Progressive MS.
  2. CMS. 2025-2026 Medicare Advantage Risk Adjustment — CMS-HCC Model v28 ICD-10-CM Mappings. 4. CMS. IPPS Final Rule FY2026 — MS-DRG Definitions Manual v43. MDC 01 logic tables.
  3. CMS. ICD-10-PCS Reference Manual FY2026. Section 0 (Central Nervous System), Section 3 (Administration).
  4. AMA. CPT Professional Edition 2026. Neurology and Medicine subsections.

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