2026 ICD-10-CM Diagnosis Code B43.1Pheomycotic brain abscess

ICD-10-CM Codes›A00–B99›B35-B49›B43

ICD-10-CM B43.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B43.1 is a billable ICD-10-CM diagnosis code for pheomycotic brain abscess. 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 infection by Cladosporium trichoides. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under CNS abscess and Fungal infections.

Code Identity

ICD-10-CM Code
B43.1
Billable Status
Yes — Valid for Submission
Code Describes
Pheomycotic brain abscess
Short Description
Pheomycotic brain abscess
Same as the full description in the CMS dataset.
Parent Code
B43
Chromomycosis and pheomycotic abscess

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB35-B49Mycoses
CategoryB43Chromomycosis and pheomycotic abscess
This CodeB43.1Pheomycotic brain abscess

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Infection by Cladosporium trichoides
  • Infection of brain caused by Form Dematiaceae
  • Phaeohyphomycosis
  • Pheohyphomycotic brain abscess

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Cerebral chromomycosis

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.

    • Abscess(connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic)
      • brain (any part) (cystic) (otogenic)
        • pheomycotic (chromomycotic)
    • Chromomycosis
      • brain abscess
    • Chromomycosis
      • cerebral
    • Infection, infected, infective(opportunistic)
      • Cladosporium
        • bantianum (brain abscess)
    • Infection, infected, infective(opportunistic)
      • Cladosporium
        • trichoides (brain abscess)

Clinical ClassificationClinical

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

CCSR NVS014
CNS abscess
Default principal diagnosis: inpatient Yes · outpatient Yes
CCSR INF004
Fungal infections
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Cerebral Phaeohyphomycosis

    cns infections caused by neurotropic dematiaceous fungi that contain melanin in their cell walls. the infections often result in brain abscess; encephalitis; and meningitis in patients who are often immunocompetent. the common causative fungi include members cladophialophora bantiana, exophiala dermatitidis, rhinocladiella mackenziei, and ochroconis gallopavum. r. mackenziei infection is seen almost exclusively in patients from the middle east.

  • Phaeohyphomycosis

    opportunistic infections caused by the dematiaceous (darkly pigmented) mitosporic fungi of alternaria, bipolaris, cladosporium, curvularia, and exophiala. these fungi have pigmented hyphae due to melanin in the cell wall. the initial subcutaneous cyst from the infection can become systemic and spread rapidly to renal, pulmonary and cerebral systems (see cerebral phaeohyphomycosis) in an immunocompromised host.

Patient EducationClinical

Abscess

An abscess is a pocket of pus. You can get an abscess almost anywhere in your body. When an area of your body becomes infected, your body's immune system tries to fight the infection. White blood cells go to the infected area, collect within the damaged tissue, and cause inflammation. During this process, pus forms.

Read the full article at MedlinePlus

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

Convert B43.1 to ICD-9-CMHistory

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

ICD-9-CM
117.2 Chromoblastomycosis
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 B43.1Overview

Is B43.1 (Chromomycosis and pheomycotic abscess) a billable code?

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

What MS-DRG does B43.1 group to?

When pheomycotic brain abscess 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 B43.1?

Under the General Equivalence Mappings, pheomycotic brain abscess converts to ICD-9-CM 117.2 (chromoblastomycosis). 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.