What is ICD-10 code B46.8?

B46.8 is the ICD-10-CM diagnosis code for Other zygomycoses. Other types of fungal infections caused by zygomycete fungi (a broader fungal family) that are not mucormycosis. It belongs to the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99). B46.8 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. B46.8 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. B46.8 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. B46.8 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 B46.8?

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 B46.8, V28 maps to Opportunistic Infections at RAF 0.381 while V24 mapped to Opportunistic Infections at RAF 0.424. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting B46.8?

Document the specific type of zygomycosis if identified Ensure this is not mucormycosis, which has its own specific codes Because B46.8 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 B46.8: Other zygomycoses

ICD-10-CM Code View

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Code lookupB46.8Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

B46.8

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

Other zygomycoses

Other types of fungal infections caused by zygomycete fungi (a broader fungal family) that are not mucormycosis.

Buddy Insight

Other zygomycoses captures infections caused by zygomycete fungi other than Mucorales, including entomophthoramycosis (Basidiobolus and Conidiobolus species).

CMS-HCC V28

Mapped

HCC 6

Opportunistic Infections

RAF 0.381

CMS-HCC V24

Mapped

HCC 6

Opportunistic Infections

RAF 0.424

ACA/HHS

Mapped

HCC 6

HHS-HCC 6

Varies by metal level

ESRD/PACE

Mapped

HCC 6

Opportunistic Infections

RAF 0.076

RXHCC

Mapped

HCC 5

Opportunistic Infections

RAF 0.468

Code Book Path

Official

B46Zygomycosis

B46.8Other zygomycoses

Inclusion Terms

Official

Entomophthoromycosis

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for B46.8 in this effective period.

Related Child Codes

Official

B46.0Pulmonary mucormycosis

B46.1Rhinocerebral mucormycosis

B46.2Gastrointestinal mucormycosis

B46.3Cutaneous mucormycosis

B46.4Disseminated mucormycosis

Includes

Official

ICD-10-CM does not list Includes notes for B46.8 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for B46.8 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for B46.8 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for B46.8 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for B46.8 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Culture or histopathologic identification of the specific zygomycete organism

Documentation that this is NOT mucormycosis (different genus within Zygomycetes)

Clinical presentation: subcutaneous nodules, facial swelling (Conidiobolus), or limb/trunk masses (Basidiobolus)

Geographic/travel history to tropical or subtropical endemic areas

MEAT Support

HCC Buddy guidance

Culture or histopathologic identification of the specific zygomycete organism

Documentation that this is NOT mucormycosis (different genus within Zygomycetes)

Clinical presentation: subcutaneous nodules, facial swelling (Conidiobolus), or limb/trunk masses (Basidiobolus)

Geographic/travel history to tropical or subtropical endemic areas

Audit Caution

HCC Buddy guidance

Confusing entomophthoramycosis with mucormycosis — they have different organisms, clinical presentations, and prognoses

Using mucormycosis codes (B46.0-B46.5) for non-Mucorales zygomycetes

Not recognizing that entomophthoramycosis can occur in immunocompetent patients, unlike classic mucormycosis

Common Mistakes

HCC Buddy guidance

B46.0-B46.5 (Mucormycosis codes) - mucormycosis is the most common zygomycosis and has its own specific codes

B46.9 (Zygomycosis, unspecified) - use only when the specific organism cannot be determined

B48.8 (Other specified mycoses) - for fungal infections not classified as zygomycoses

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 B46.8 an HCC code?

Yes. B46.8 (Other zygomycoses) 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: B46.8 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: B46.8
Description: Other zygomycoses
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 B46.8 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for B46.8

For B46.8 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 B46.8 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

B46.8 is the ICD-10-CM diagnosis code for other zygomycoses. Other types of fungal infections caused by zygomycete fungi (a broader fungal family) that are not mucormycosis. B46.8 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, B46.8 maps to Opportunistic Infections (HCC 6) with a community, non-dual, aged base RAF weight of 0.381. Under the older V24 model, B46.8 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.

Document the specific type of zygomycosis if identified. Because B46.8 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 B46.8 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Document the specific type of zygomycosis if identified
•Ensure this is not mucormycosis, which has its own specific codes

Clinical Significance

Other zygomycoses captures infections caused by zygomycete fungi other than Mucorales, including entomophthoramycosis (Basidiobolus and Conidiobolus species). These infections differ from mucormycosis in that they can affect immunocompetent patients and tend to be more chronic and indolent. They are predominantly found in tropical regions.

Documentation Requirements

✓Culture or histopathologic identification of the specific zygomycete organism
✓Documentation that this is NOT mucormycosis (different genus within Zygomycetes)
✓Clinical presentation: subcutaneous nodules, facial swelling (Conidiobolus), or limb/trunk masses (Basidiobolus)
✓Geographic/travel history to tropical or subtropical endemic areas
✓Immune status of the patient documented

Commonly Confused Codes

•B46.0-B46.5 (Mucormycosis codes) - mucormycosis is the most common zygomycosis and has its own specific codes
•B46.9 (Zygomycosis, unspecified) - use only when the specific organism cannot be determined
•B48.8 (Other specified mycoses) - for fungal infections not classified as zygomycoses