2026 ICD-10-CM Diagnosis Code B40.9Blastomycosis, unspecified

ICD-10-CM Codes›A00–B99›B35-B49›B40

ICD-10-CM B40.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

B40.9 is a billable ICD-10-CM diagnosis code for blastomycosis, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 791, 793, 867 through 869. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 14 closely related codes. Coders also document this condition as blastomycosis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Fungal infections.

Code Identity

ICD-10-CM Code
B40.9
Billable Status
Yes — Valid for Submission
Code Describes
Blastomycosis, unspecified
Short Description
Blastomycosis, unspecified
Same as the full description in the CMS dataset.
Parent Code
B40
Blastomycosis

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionB35-B49Mycoses
CategoryB40Blastomycosis
This CodeB40.9Blastomycosis, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Blastomycosis
  • Blastomycotic prostatitis
  • Infection by Blastomyces dermatitidis
  • Non-bacterial prostatitis
  • Urogenital blastomycosis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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

  • Blastomycosis

    a fungal infection by blastomyces that may appear in two forms: 1, a primary lesion characterized by the formation of a small cutaneous nodule and small nodules along the lymphatics that may heal within several months; and 2, chronic granulomatous lesions characterized by thick crusts, warty growths, and unusual vascularity and infection in the middle or upper lobes of the lung.

  • Lobomycosis

    a chronic, fungal, subcutaneous infection endemic in rural regions in south america and central america. the causal organism is lacazia labol.

  • Paracoccidioidomycosis

    a mycosis affecting the skin, mucous membranes, lymph nodes, and internal organs. it is caused most often by paracoccidioides brasiliensis. it is also called paracoccidioidal granuloma.

  • Blastomyces

    a genus of onygenacetous mitosporic fungi whose perfect state is ajellomyces (see onygenales). the species blastomyces dermatitidis (perfect state is ajellomyces dermatitidis) causes blastomycosis.

  • Blastomycosis

    a fungal infection caused by inhalation of spores of blastomyces dermatitidis. it presents with flu-like symptoms including fever, chills, cough, pleuritic chest pain and myalgias. it may lead to a chronic granulomatous pulmonary infection and disseminate to other anatomic sites including skin, nervous system and bones.

  • North American Blastomycosis|Blastomyces Dermatitidis Infection

    a pulmonary disease resulting from infection with blastomyces dermatitidis, which is prevalent in north america.

Patient EducationClinical

Fungal Infections

If you have ever had athlete's foot or a yeast infection, you can blame a fungus. A fungus is a primitive organism. Mushrooms, mold and mildew are examples. Fungi live in air, in soil, on plants and in water. Some live in the human body. Only about half of all types of fungi are harmful.

Read the full article at MedlinePlus

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

Convert B40.9 to ICD-9-CMHistory

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

ICD-9-CM
116.0 Blastomycosis
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 B40.9Overview

What is the ICD-10 code for blastomycosis, unspecified?

The ICD-10-CM code for blastomycosis, unspecified is B40.9 (sometimes written as B409). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is B40.9 (Blastomycosis) a billable code?

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

What MS-DRG does B40.9 group to?

When blastomycosis, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 791, 793, 867, 868, 869, with relative weights from 0.7297 to 4.1696 depending on complications. Higher weights mean higher Medicare reimbursement.

Is B40.9 a CC or MCC?

CMS lists B40.9 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 14 closely related codes in its exclusion list.

What is the ICD-9 equivalent of B40.9?

Under the General Equivalence Mappings, blastomycosis, unspecified converts to ICD-9-CM 116.0 (blastomycosis). The mapping is approximate, so confirm the match fits the documentation.