2026 ICD-10-CM Diagnosis Code A42Actinomycosis

ICD-10-CM Codes›A00–B99›A30-A49›A42

ICD-10-CM A42
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A42 is a non-billable ICD-10-CM category code for actinomycosis, so it cannot be submitted on claims. Use a more specific code from this category instead, such as A42.0, A42.1, A42.2, and A42.7.

Code Identity

ICD-10-CM Code
A42
Billable Status
No — Non-Billable Category
Code Describes
Actinomycosis
Chapter
A30-A49
Other bacterial diseases

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA30-A49Other bacterial diseases
CategoryA42Actinomycosis
This CodeA42Actinomycosis

Specific Coding for ActinomycosisOverview

Non-specific codes like A42 require more characters. Use one of these billable codes instead:

  • Use A42.0 for Pulmonary actinomycosis

  • Use A42.1 for Abdominal actinomycosis

  • Use A42.2 for Cervicofacial actinomycosis

  • Use A42.7 for Actinomycotic sepsis

  • A42.8 for Other forms of actinomycosis

  • Use A42.81 for Actinomycotic meningitis

  • Use A42.82 for Actinomycotic encephalitis

  • Use A42.89 for Other forms of actinomycosis

  • Use A42.9 for Actinomycosis, unspecified

Tabular List NotesGuidance

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

Type 1 Excludes

Clinical InformationClinical

  • Actinomycosis

    infections with bacteria of the genus actinomyces.

  • Actinomycosis, Cervicofacial

    a form of actinomycosis characterized by slow-growing inflammatory lesions of the lymph nodes that drain the mouth (lumpy jaw), reddening of the overlying skin, and intraperitoneal abscesses.

  • Actinomyces

    a genus of gram-positive, rod-shaped bacteria whose organisms are nonmotile. filaments that may be present in certain species are either straight or wavy and may have swollen or clubbed heads.

  • Actinomycosis

    an infectious process caused by bacteria of the actinomyces species. it is characterized by the formation of purulent and painful abscesses in the mouth, lungs and gastrointestinal tract.

Patient EducationClinical

Bacterial Infections

Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.

The full article covers:

  • What are bacteria?
  • How do bacterial infections spread?
  • What are the treatments for bacterial infections?
  • Can bacterial infections be prevented?

Read the full article at MedlinePlus

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

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 A42Overview

Is A42 (Actinomycosis) a billable code?

No. This is a category header that groups the codes for actinomycosis, and headers cannot be submitted on claims. Claims for actinomycosis need a more specific code from this category, such as A42.0, A42.1, and A42.2.