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B46.3 ICD-10-CM Code: Cutaneous mucormycosis

B46.3 maps to CMS-HCC V28 6 (RAF 0.381). Documentation must support MEAT. MEAT criteria · RAF calculator · free HCC coding tools

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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Mycoses (B35-B49)

B46.3

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

Cutaneous mucormycosis

A serious fungal infection of the skin caused by mucormycosis, which is a type of mold that can invade and damage skin tissue. This condition typically occurs in people with weakened immune systems or uncontrolled diabetes.

Buddy the Bee presenting code insight

Buddy Insight

Cutaneous mucormycosis is the form most commonly seen in immunocompetent patients, typically following trauma, burns, or surgical wounds with soil contamination.

CMS-HCC V28

HCC 6

RAF 0.381

CMS-HCC V24

HCC 6

RAF 0.424

ACA/HHS

HCC 6

Varies by metal level

ESRD/PACE

HCC 6

RAF 0.076

RXHCC

HCC 5

RAF 0.468

Code Book Path

Official
B46Zygomycosis
B46.3Cutaneous mucormycosis

Inclusion Terms

Official
  • Subcutaneous mucormycosis

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for B46.3 in this effective period.

Related Child Codes

Official
B46.0Pulmonary mucormycosis
B46.1Rhinocerebral mucormycosis
B46.2Gastrointestinal mucormycosis
B46.4Disseminated mucormycosis
B46.5Mucormycosis, unspecified

Includes

Official

ICD-10-CM does not list Includes notes for B46.3 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for B46.3 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for B46.3 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for B46.3 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for B46.3 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Wound or skin biopsy confirming Mucorales with tissue invasion
Site, size, and depth of cutaneous involvement documented with laterality
History of trauma, burns, or surgical wound with contamination
Assessment for underlying immunocompromise (diabetes, transplant, neutropenia)

MEAT Support

HCC Buddy guidance
Wound or skin biopsy confirming Mucorales with tissue invasion
Site, size, and depth of cutaneous involvement documented with laterality
History of trauma, burns, or surgical wound with contamination
Assessment for underlying immunocompromise (diabetes, transplant, neutropenia)

Audit Caution

HCC Buddy guidance
Coding as generic wound infection when tissue biopsy reveals mucormycosis — specific fungal etiology must be captured
Not evaluating for deep tissue or bone extension beneath the cutaneous lesion
Failing to assess immunocompromised patients for disseminated disease when cutaneous mucormycosis is found
Missing the diagnosis in burn patients where wound discoloration is attributed to ischemia rather than fungal invasion

Common Mistakes

HCC Buddy guidance
B46.0-B46.2 (Site-specific mucormycosis) - other forms affect lung, sinus/brain, or gastrointestinal tract
B46.4 (Disseminated mucormycosis) - use if cutaneous disease has extended systemically
L08.89 (Other specified local infections of skin and subcutaneous tissue) - do not use generic skin infection code when fungal etiology is confirmed

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 B46.3 an HCC code?

Yes. B46.3 (Cutaneous mucormycosis) maps to Opportunistic Infections under the CMS-HCC V28 risk adjustment model (and Opportunistic Infections under V24), with a community non-dual aged RAF of 0.381. It is billable for payment year 2026.

Coder answer: B46.3 is billable and maps to V28 HCC 6, Opportunistic Infections. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
B46.3
Description
Cutaneous mucormycosis
HCC (V28)
HCC 6 — Opportunistic Infections
RAF
0.381
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 6, Opportunistic Infections
0.381
V24HCC 6, Opportunistic Infections
0.424
ESRDHCC 6, Opportunistic Infections
0.076
RxHCCHCC 5, Opportunistic Infections
0.468

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 B46.3 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for B46.3

For B46.3 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 B46.3 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

B46.3 is the ICD-10-CM diagnosis code for cutaneous mucormycosis. A serious fungal infection of the skin caused by mucormycosis, which is a type of mold that can invade and damage skin tissue. This condition typically occurs in people with weakened immune systems or uncontrolled diabetes. B46.3 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering mycoses (b35-b49).

Under the CMS-HCC V28 risk adjustment model, B46.3 maps to Opportunistic Infections (HCC 6) with a community, non-dual, aged base RAF weight of 0.381. Under the older V24 model, B46.3 mapped to the same category but with a base RAF weight of 0.424, V28 recalibrated weights across the entire model. 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.

Verify the anatomical site of the cutaneous infection and use appropriate laterality codes if applicable (left, right, or bilateral). Because B46.3 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 B46.3 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Verify the anatomical site of the cutaneous infection and use appropriate laterality codes if applicable (left, right, or bilateral)
  • •Investigate the underlying cause or risk factor (such as immunocompromised status, diabetes, or transplant status) as these may require additional codes for complete clinical documentation

Clinical Significance

Cutaneous mucormycosis is the form most commonly seen in immunocompetent patients, typically following trauma, burns, or surgical wounds with soil contamination. Unlike other mucormycosis forms, primary cutaneous disease has the best prognosis (approximately 70% survival) when treated early with surgical debridement and antifungal therapy. However, it can progress to disseminated disease in immunocompromised patients.

Documentation Requirements

  • ✓Wound or skin biopsy confirming Mucorales with tissue invasion
  • ✓Site, size, and depth of cutaneous involvement documented with laterality
  • ✓History of trauma, burns, or surgical wound with contamination
  • ✓Assessment for underlying immunocompromise (diabetes, transplant, neutropenia)
  • ✓Evidence of local extension vs contained disease documented
  • ✓Surgical debridement performed and extent documented

Commonly Confused Codes

  • •B46.0-B46.2 (Site-specific mucormycosis) - other forms affect lung, sinus/brain, or gastrointestinal tract
  • •B46.4 (Disseminated mucormycosis) - use if cutaneous disease has extended systemically
  • •L08.89 (Other specified local infections of skin and subcutaneous tissue) - do not use generic skin infection code when fungal etiology is confirmed

Child Codes

B46.0Pulmonary mucormycosis
HCC 6
B46.1Rhinocerebral mucormycosis
HCC 6
B46.2Gastrointestinal mucormycosis
HCC 6
B46.3Cutaneous mucormycosis
HCC 6
B46.4Disseminated mucormycosis
HCC 6
B46.5Mucormycosis, unspecified
HCC 6
B46.8Other zygomycoses
HCC 6
B46.9Zygomycosis, unspecified
HCC 6

Code Hierarchy

└B46Zygomycosis└B46.3Cutaneous mucormycosis
└B46.3Cutaneous mucormycosis

Because B46.3 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.

B46.3 maps to CMS-HCC V28 category 6, Opportunistic Infections. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. Because B46.3 carries a payment HCC, you can see what it adds to a RAF score and check the documentation the chart needs before it is submitted.

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Open B46.3 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

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