B46.3
BillableCutaneous mucormycosis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is B46.3 an HCC code?
Yes. B46.3 maps to Opportunistic Infections under the CMS-HCC V28 risk adjustment model (and Opportunistic Infections under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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.
MEAT Criteria for B46.3
For B46.3to 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.
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