What is ICD-10 code M46.35?

M46.35 is the ICD-10-CM diagnosis code for Infection of intervertebral disc (pyogenic), thoracolumbar region. A bacterial infection of the intervertebral disc located at the junction between the mid-back and lower back (thoracolumbar region). M46.35 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. M46.35 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. M46.35 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. M46.35 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 M46.35?

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. For M46.35, V28 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis at RAF 0.479 while V24 mapped to Bone/Joint/Muscle Infections/Necrosis at RAF 0.401. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting M46.35?

Thoracolumbar region spans T12-L1; confirm this is the documented location Document any associated symptoms like back pain or neurological deficits Because M46.35 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.

2026 ICD-10-CM M46.35: Infection of intervertebral

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Code lookupM46.35Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Spondylopathies (M45-M49)

M46.35

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

Infection of intervertebral disc (pyogenic), thoracolumbar region

A bacterial infection of the intervertebral disc located at the junction between the mid-back and lower back (thoracolumbar region).

Buddy Insight

Thoracolumbar junction discitis presents unique challenges due to the biomechanical stress at this spinal transition zone and potential for both thoracic and lumbar complications.

CMS-HCC V28

Mapped

HCC 92

Bone/Joint/Muscle/Severe Soft...

RAF 0.479

CMS-HCC V24

Mapped

HCC 39

Bone/Joint/Muscle Infections/...

RAF 0.401

ACA/HHS

Mapped

HCC 55

HHS-HCC 55

Varies by metal level

ESRD/PACE

Mapped

HCC 39

Bone/Joint/Muscle Infections/...

RAF 0.092

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

M46Other inflammatory spondylopathies

M46.3Infection of intervertebral disc (pyogenic)

M46.35Infection of intervertebral disc (pyogenic), thoracolumbar region

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M46.35 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M46.35 in this effective period.

Related Child Codes

Official

M46.30Infection of intervertebral disc (pyogenic), site unspecified

M46.31Infection of intervertebral disc (pyogenic), occipito-atlanto-axial region

M46.32Infection of intervertebral disc (pyogenic), cervical region

M46.33Infection of intervertebral disc (pyogenic), cervicothoracic region

M46.34Infection of intervertebral disc (pyogenic), thoracic region

Includes

Official

ICD-10-CM does not list Includes notes for M46.35 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M46.35 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M46.35 in this effective period.

Use Additional

Official

code (B95-B97) to identify infectious agent.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M46.35 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Specific thoracolumbar junction location (T12-L1)

Pyogenic bacterial infection confirmation

MRI findings showing disc space enhancement and edema

Assessment of lumbar lordosis and thoracic alignment

MEAT Support

HCC Buddy guidance

Specific thoracolumbar junction location (T12-L1)

Pyogenic bacterial infection confirmation

MRI findings showing disc space enhancement and edema

Assessment of lumbar lordosis and thoracic alignment

Audit Caution

HCC Buddy guidance

Assigning to pure thoracic or lumbar regions instead of junction code

Missing the biomechanical significance of transitional zone infection

Failing to document both thoracic and lumbar neurological assessment

Not capturing unique healing challenges at this location

Common Mistakes

HCC Buddy guidance

M46.34 — Thoracic region when infection purely thoracic

M46.36 — Lumbar region when infection purely lumbar

M46.55 — Other infective spondylopathies same region when non-bacterial

M43.27 — Fusion of spine, lumbosacral region when describing treatment outcome

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is M46.35 an HCC code?

Yes. M46.35 (Infection of intervertebral disc (pyogenic), thoracolumbar region) maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24), with a community non-dual aged RAF of 0.479. It is billable for payment year 2026.

Coder answer: M46.35 is billable and maps to V28 HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: M46.35
Description: Infection of intervertebral disc (pyogenic), thoracolumbar region
HCC (V28): HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
RAF: 0.479
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis

0.479

V24HCC 39, Bone/Joint/Muscle Infections/Necrosis

0.401

ESRDHCC 39, Bone/Joint/Muscle Infections/Necrosis

0.092

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.

Work M46.35 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for M46.35

For M46.35 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 M46.35 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M46.35 is the ICD-10-CM diagnosis code for infection of intervertebral disc (pyogenic), thoracolumbar region. A bacterial infection of the intervertebral disc located at the junction between the mid-back and lower back (thoracolumbar region). M46.35 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering spondylopathies (m45-m49).

Under the CMS-HCC V28 risk adjustment model, M46.35 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.479. Under the older CMS-HCC V24 model, M46.35 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 39) with a community, non-dual, aged base RAF weight of 0.401. 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.

Thoracolumbar region spans T12-L1; confirm this is the documented location. Because M46.35 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 M46.35 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Thoracolumbar region spans T12-L1; confirm this is the documented location
•Document any associated symptoms like back pain or neurological deficits

Clinical Significance

Thoracolumbar junction discitis presents unique challenges due to the biomechanical stress at this spinal transition zone and potential for both thoracic and lumbar complications. This location often experiences delayed healing and may require prolonged treatment courses.