2026 ICD-10-CM Diagnosis Code B46.1Rhinocerebral mucormycosis

ICD-10-CM Codes›A00–B99›B35-B49›B46

ICD-10-CM B46.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B46.1 is a billable ICD-10-CM diagnosis code for rhinocerebral mucormycosis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 867 through 869. Coders also document this condition as fungal infection of cerebrum. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Fungal infections.

Code Identity

ICD-10-CM Code
B46.1
Billable Status
Yes — Valid for Submission
Code Describes
Rhinocerebral mucormycosis
Short Description
Rhinocerebral mucormycosis
Same as the full description in the CMS dataset.
Parent Code
B46
Zygomycosis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB35-B49Mycoses
CategoryB46Zygomycosis
This CodeB46.1Rhinocerebral mucormycosis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Fungal infection of cerebrum
  • Rhinocerebral mucormycosis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Mucormycosis
      • rhinocerebral

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF004
Fungal infections
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Zygomycosis

    infection in humans and animals caused by fungi in the class zygomycetes. it includes mucormycosis and entomophthoramycosis. the latter is a tropical infection of subcutaneous tissue or paranasal sinuses caused by fungi in the order entomophthorales. phycomycosis, closely related to zygomycosis, describes infection with members of phycomycetes, an obsolete classification.

  • Mucormycosis

    infection in humans and animals caused by any fungus in the order mucorales (e.g., rhizopus; mucor; cunninghamella; apophysomyces; absidia; saksenaea and rhizomucor) there are many clinical types associated with infection including central nervous system, lung, gastrointestinal tract, skin, orbit and paranasal sinuses. in humans, it usually occurs as an opportunistic infection.

Patient EducationClinical

Brain Diseases

Your brain is the control center of your body. It controls your thoughts, memory, speech, and movement. It regulates the function of many organs. It's part of your nervous system, which also includes your spinal cord and peripheral nerves. The nervous system sends signals between your brain and the rest of the body.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert B46.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
117.7 Zygomycosis
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About B46.1Overview

Is B46.1 (Zygomycosis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report rhinocerebral mucormycosis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does B46.1 group to?

When rhinocerebral mucormycosis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 867, 868, 869, with relative weights from 0.7297 to 2.0932 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of B46.1?

Under the General Equivalence Mappings, rhinocerebral mucormycosis converts to ICD-9-CM 117.7 (zygomycosis). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.